Racecar Engineering Le Mans 2021

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The new era starts here >> New cars analysed

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LE MANS 24 HOURS 2021 | COMMENT

CONTENTS 04 TOYOTA GR010 Can the Japanese firm extend its LMP winning streak with its stunning Hypercar?

12 GLICKENHAUS 007C US privateer takes on the big guns at the Le Mans 24 Hours

34 CORVETTE C8R How will the US mid-engine supercar fare on its Le Mans debut?

46 REMEMBERING 1991 On the 30th anniversary of Mazda’s famous win we take an in-depth look at its rotary racers

XPB

20 BALANCING HYPERCARS The man behind the WEC BoP system runs us through its logic

28 TYRE DEVELOPMENT The differing philosophies of Michelin and Goodyear at Le Mans

T

here have been plenty of talking points in the paddock at Le Mans in 2021, surrounding not only the new era of Hypercars at the race, but also the future of prototype and GT racing. At a press conference on Friday morning ahead of the race, the FIA and ACO confirmed that they would switch focus in GT racing to GT3 cars for the 2024 season. IMSA has already confirmed that these cars would no longer race in the US at the end of this year, meaning that Porsche, Corvette and Ferrari have one more year in the FIA WEC, and at Le Mans, with their GTEs. During the conference, the ACO also confirmed that it has delayed the introduction of its Hydrogen class to 2025, but in the interim announced that with partners Total Energies, it will feature renewable fuel in both the Le Mans 24 hours and truck racing in 2022 to help promote the environmentally aware agenda.

The fuel will reduce carbon emissions by up to 60 per cent, says Total. This is a welcome addition to the future of fuels debate, with no mention of electric, that has already been tried in endurance racing (with the ZEOD, which led to no continued racing programme) and the retaining of the internal combustion engine formula.

There was also a firm commitment to the LMP2 category that will be introduced in 2024. These cars will, insists the FIA and ACO, be based on the LMDh spine, and they are convinced that they will be able to be turned into cost-effective customer racing cars. This category will remain as the top class in the European and Asian Le Mans Series, and the cars will also be eligible to race in the FIA WEC and IMSA. It rather stuck a stick in the eye of some of the LMDh manufacturers, who were hoping that their cars would be able to be sold into ELMS and Asia, but does favour the smaller prototype teams that want to continue with their racing programmes.

The conference struck a positive note in promoting the future of the race, but there are still details to be sorted out. GM cancelled its planned press conference, where it was expected to confirm Cadillac coming to Le Mans and Corvette to race in GT3, as until the ACO could commit to a firm set of regulations surrounding the new GT class and pro and am categories, it preferred to wait. Alpine has yet to confirm its racing plans, although it, too, is expected to opt for an LMDh programme.

The fuel will reduce carbon emissions by up to 60 per cent, says Total

Andrew Cotton, Editor Racecar Engineering • Le Mans 2021 3

RACECAR FOCUS | TOYOTA GR010 HYPERCAR

One step beyond The Toyota was the first of the new breed of Hypercars to break cover, built to a completely new rule set that sees cars longer, wider, heavier, less powerful and supposedly cheaper to build and run than before

‘Probably the positive thing of the new regulations is that the aero is free’ John Litjens, project leader for Hypercar

4 Le Mans 2021 • Racecar Engineering

Toyota launched its new Hypercar in January, and is set to defend its World Championship and Le Mans titles in the new era of endurance racing

By ANDREW COTTON

T

oyota in January took the wraps off its new Le Mans challenger, the GR010 hybrid, with which it will compete in the FIA World Endurance Championship until at least 2025. Toyota was the first to reveal its new Hypercar, and it has since gone on to win each of the three rounds of the WEC leading up to Le Mans at Spa, Portimao and Monza.

The GR010 is built to a totally new set of regulations and therefore is longer, wider, heavier and less powerful than the outgoing TS050. The car is expected to be around 10 seconds per lap slower at Le Mans than the TS050 by regulation, and five seconds slower on a regular WEC circuit.

The GR010 is powered by a 3.5-litre V6 engine that produces a maximum power output of no more than 500kW by regulation, whether from solely the engine or a combination of engine and hybrid system, a loss of 33 per cent compared to the TS050.

The GR010 also carries less technology than its predecessor, making it cheaper to run. It features only one energy recovery system at the front, for example, and the interlinked suspension has gone, replaced by independent suspension on the four corners.

Reduced advantage A new Balance of Performance system will govern the pace of the Hypercars, reducing the advantage for manufacturers.

The development of this racecar will directly influence the roadgoing supercar Gazoo Racing and Toyota showed in concept at Le Mans in September.

The new regulations have targeted a reduction in costs, so fewer rare materials have been used in the construction of the car.

The centre of gravity is fixed for the gearbox, monocoque and engine by regulation, which for Toyota led to extensive re-design work and strengthening of parts for its 2021 challenger when compared to the TS050.

Aerodynamically, the GR010 is particularly striking, with large gaps between the front splitter and the bottom of the monocoque, and at the rear between the engine cover and diffuser. These are designed to ensure adequate cooling, while maintaining smooth airflow over the bodywork.

A further cost-cutting regulation is that there is no variation of the bodywork from race to race. So this is the body that will be used at Le Mans, as well as at shorter circuits such as Fuji. Cooling is therefore an important consideration as the car will also race in high temperatures without modification, and without overheating.

Racecar Engineering • Le Mans 2021 5

RACECAR FOCUS | TOYOTA GR010 HYPERCAR The regulations feature a set of performance windows into which each of the Hypercars, be they prototype or road car based, must fit. One of those is a point on the lift / drag graph that dictates the aerodynamics of the car and is not, according to Toyota, challenging to meet.

With power limited and closely monitored by the FIA using standard telemetry and torque sensors on each of the driveshafts, this is a totally different animal to the team’s former LMP1 car, and has been built with entirely new objectives.

All-new engine The switch to a 3.5-litre unit was driven by the fact it will be required to deliver up to 500kW of power, more than the TS050. The increase in capacity is also to bring the engine in line with the planned production car, which would have struggled with the smaller capacity engine.

‘The reason [for the change] is there is quite a significant change in powertrain regulation with the switch of power dominance from hybrid side to combustion engine,’ says Gazoo Racing’s technical director, Pascal Vasselon. ‘We need to achieve a given power target, which is 500kW at the moment, and we know we can only temporarily use the 200kW of

hybrid power, so this means the combustion engine has to be able to deliver 500kW. ‘Considering that within the Balance of Performance category reliability is even more important than it was before, the decision to go to a bigger engine was quite logical. More power was needed, as were even higher reliability standards.’

The decision to stick with a V6 was also driven by the packaging requirements for the GR010. Even though the wheelbase is slightly longer than the car’s predecessor that would allow for a longer engine, the cockpit has been moved further away from the centre line of the front wheels.

The mandated battery position is behind the driver. With the fuel cell located in a similar position, there was no option for Toyota to go for more cylinders.

‘We had to do something with the road car and the clear goal from management was to share the main components between the two, so this is a totally new engine,’ explains John Litjens, project leader for the Le Mans programmes including Hypercar.

One of the challenges for the engine will be the switch from full ICE power to combined power delivery from the ICE and hybrid system, which may only take place over 120kph in the dry, and between 140-160kph in the wet in order to protect

With just one body kit allowed for the whole season, and the car designed with the roadgoing variant in mind, the rear fin was initially left off, but was later put back in as part of the car’s development process. Rear wing end plates are noticeably smaller than before

6 Le Mans 2021 • Racecar Engineering

‘The architecture is the most efficient one within the regulations, but we have to bear in mind that we are in Balance of Performance’ Pascal Vasselon, technical director at Gazoo Racing

the two-wheel drive competitors. At no point may the power output exceed 500kW, and so the control systems will need to be able to switch seamlessly between the two.

‘The way to handle the hybrid system is totally different compared to LMP1,’ says Vasselon. ‘Now we are talking about a maximum combined power, while in LMP1 the power of the hybrid system was adding to the combustion engine. Now it is either or. It means that if we use 200kW from the hybrid, we can only use 300kW from the combustion engine.

TECH SPEC: Toyota GR010 Hypercar Bodywork: Carbon fibre composite

With more freedom by regulation, the above roof air intake is set much further back compared to the TS050

Gearbox: Transverse with seven gears, sequential Driveshafts: Constant velocity tripod plunge-joint Clutch: Multidisc Differential: Mechanical locking differential Suspension: Independent front and rear double wishbone, pushrod system Springs: Torsion bar Anti-roll bars: Front and rear Steering: Hydraulically assisted Brakes: Akebono monoblock alloy calipers with carbon ventilated discs Rims: RAYS magnesium alloy 13 x 18in Tyres: Michelin radial 31/71-18 Length: 4900mm Width: 2000mm Height: 1150mm Weight: 1040kg Fuel capacity: 90 litres Engine: V6 direct injection twin turbo Valves: Four per cylinder Engine capacity: 3.5 litres Fuel: Petrol Engine power: 500kW / 680ps Hybrid power: 200kW / 272ps Battery: High-powered Toyota lithium-ion Front motor / inverter: Aisin AW / Denso

The regulations are a set of performance windows into which each of the five categories of car must fit

Only one adjustable aero device is now allowed, and Toyota chose to use the rear wing

Racecar Engineering • Le Mans 2021 7

RACECAR FOCUS | TOYOTA GR010 HYPERCAR ‘A hybrid system will remain more fuel efficient, and the hybrid system at the front allows four-wheel drive functionality.

The architecture is the most efficient one within the regulations, but we have to bear in mind that we are in Balance of Performance, so these benefits will be compensated by other handicaps.’

Hybrid system The hybrid system is also new compared to the TS050, with different requirements compared to its predecessor. The MGU-K is still mounted in the footwell of the chassis, as it was before, but where the old hybrid system was limited to a maximum power output of 300kW, it was actually the recharging capability that drove the size of the battery.

‘We were running much higher power in the recovery and boost in the LMP1,’ confirms Vasselon. ‘Now we are at 200kW for recovery and boost, so it is clearly a different battery.

[The limit of 300kW of the TS050] was only for boost. We were going between 500-600kW in recovery [in the LMP1 era] and this was sizing the battery. It is a large reduction in the power requirement for the battery.’

In terms of power deployment, there are surprisingly few regulations and manufacturers will be largely free to decide where and by how much to boost.

‘There is quite a lot of freedom in how to deploy the front motor, considering the main regulation is a catch-all regulation at 500kW, but within this we can do pretty much what we want,’ says Vasselon.

‘We can choose to boost continually throughout the lap at the front, or we can decide to boost at corner exit and use 200kW and nothing five seconds later. We have a lot of freedom, considering the main limitation is the maximum combined power.’

Chassis re-think The chassis for the GR010 is the first to be developed by the team since the start of the TS050 programme in 2016, and required a fundamental re-think due to the increase in weight and correlation to the road car. The racecar tips the scales at 1040kg by regulation and that then is balanced. The engine, gearbox and monocoque are all heavier than the TS050, and the team has strengthened the more sensitive parts of the car accordingly.

‘The gearbox increased in weight by quite a lot because there is a minimum weight by regulations, and there is a minimum centre of gravity, too,’ says Litjens.

‘The monocoque also has a minimum weight and centre of gravity, so you had to put weight on [there], and the rest of the weight went onto reliability and robustness in case of contact. We have load cases [design targets] and a safety factor [built into them], and we increased the safety factor.’

8 Le Mans 2021 • Racecar Engineering

Airflow at the side of the car is directed through the radiators and into a Coke bottle effect, starting ahead of the rear wheels

However, while the architecture was being finalised, the aero work was simpler than expected. ‘Probably the positive thing of the new regulations is that the aero is free,’ confirms Litjens. ‘For sure, the aero numbers to meet the Balance of Performance boundaries are not that challenging if you compare to where we were with the LMP1 racecars, but we had the opportunity to create the link with the roadgoing Hypercars, and with the people in Japan working on these cars. From our side we put some positive things in, because for a roadgoing Hypercar you want some proper downforce.’

The gap between the front splitter and the bottom of the monocoque, for example, is large, and one of the challenges of the design team was to keep that area clear of driveshafts, suspension components and the motor generator unit.

‘From an aero point of view, you are almost panicking about things not disturbing

In addition to the reduction in the number of body kits, the new regulations also stipulate only one adjustable aerodynamic device can be used the airflow,’ says Litjens. ‘The aero efficiency and downforce numbers were not that challenging, so we worked on the suspension kinematics, and you have the packaging of the front motor and monocoque so that sets the driveshaft position.

‘Also in play was the torque sensors, which are not small and are mandatory, and you need clearance, and so this all defined the aero. The numbers were not critical, though, so we didn’t have an issue with that.’

Aero devices In addition to the reduction in the number of body kits, the new regulations also stipulate only one adjustable aerodynamic device can be used. For Toyota, it was a tough call to decide between fixing the rear wing in place, or use a flap at the rear of the front diffuser to change aero balance, and that decision was not taken until after Christmas.

‘Due to the regulations, you have to freeze all of your bodywork and have only one adjustable device, and this can be the front wing flap or the rear wing,’ confirms Litjens.

‘Our car will have the rear wing adjuster. In the end, we tried to get clean aero, especially

Driver’s view, with Sebastien Buemi Q: What is the GR010 like to drive?

A: It is different to what I was used to. The restriction of fuel per lap is gone, so it gives you the feeling that we are back to pure racing where you brake as late as you can, as hard as you can, and don’t have to save fuel and recover as much as possible.

You still recover energy, but you don’t have to adapt your driving style to maximise the effect of the hybrid system. It is a lot of pleasure because it is back to what it was years ago.

The car is heavier and less powerful, but nice to drive. There are many things we were able to improve over the last car.

Q: As a driver, what is it like with that added weight and less power?

A: The four-wheel drive is only useable above 120kph, so you don’t feel that same acceleration out of a 50kph corner, but we maximise what we have. You feel the additional weight when you brake, but the downforce and mechanical grip in lowspeed corners is impressive.

The car is two metres wide again, so it feels like a big car, and the mechanical grip is, if anything, better than the TS050. In Portimao the car feels big, but for Le Mans and Spa it will not be any issue at all.

We want to win Le Mans, so of course we want it to be good there and we have only one aero kit, so the car that you homologate, that’s it. A few years ago, we had aero kits for pretty much every kind of track, then we had two for the year, and now we have only one for the whole year. It is going to feel much better on a track like Le Mans than a track like Portimao.

Though the new car is heavier and less powerful, and has a limit on downforce, drivers report it is highly competent and exciting to drive, and will especially suit a track like Le Mans

Q: Can you feel the difference on the brake pedal with an hydraulic and electronic system?

A: It is a bit of a different brake feel, but for a different reason. Before, we had end-ofstraight recovery and we had to do some of that to go to 8MJ. Now you arrive flat out and brake hard, so that feels completely different. Before, there was a deceleration, not a big brake. Now you have slightly less assistance with one motor on the front and nothing on the rear, so you feel you need to press the brake harder, but it is not an issue.

We are fine tuning it now.

Q: How does it work in traffic, will it be easier or more difficult?

A: You will not suffer the point where the GTs and LMP2 overtake you on the fuel cut as we used to have [at the end of the straight], but you also don’t have the very strong boost. You could all of a sudden go from 500bhp to 1000bhp and you could overtake where you wanted. Now you have 600bhp from start to finish, but you don’t have the fuel cut.

Driving in traffic will therefore be slightly easier because they don’t have to look at your rear lights flashing to see if you are recovering energy, but sometimes you could see a GT entering Porsche Curves, and push a button to get it done. Now, if you can do it on the momentum then fine, but if not you are behind all the way through.

Q: How does the new suspension system affect driving?

A: The car is so different to how it used to be that it is very difficult to make a proper comparison. The car is heavier, limited fourwheel drive and has a limit on downforce.

The interlinked suspension [on the old car] was to improve the aero. At slow speed, this car is amazing, and at high speed it is slower because you have less downforce and the car is heavier. For Le Mans, the downforce is pretty good compared to what we used to have. It will be very close to what we had there, and potentially better than before, but lower on other tracks because we don’t have the other aero packages.

Q: How are the new tyres?

A: You would be surprised the good work [Michelin] have done. They need to find the right compromise between durability and not be too risky, but they have lots of experience and know what to do.

The tyres are a bit heavier, but that might come from the fact the car is heavier and they want to be sure it is safe.

Racecar Engineering • Le Mans 2021 9

RACECAR FOCUS | TOYOTA GR010 HYPERCAR because of the importance of consistent aero. In LMP1, 2 and 3 you struggle for this, so you have a lot of flaps, turning vanes and winglets that on long runs take tyre marbles and so your aero degrades. Our philosophy was to get a car as clean as possible.’

The nose of the car remains high, although in comparison with the TS050 the driver’s legs are actually lower than before. The discussions about more upright seating positions ended early on when the plans for new regulations for 2018 were shelved following the withdrawal of Porsche which push regulators to cut costs. Such a change in seating position would have had a knock-on effect on the height of the car.

With clean airflow through the nose and channelled around the monocoque, it then feeds through the radiators mounted at the side before following a Coke bottle shape, starting ahead of the rear wheels and ending between them.

‘The floor is cut back because the air goes above the splitter, between the chassis and the floor, and then into the radiator duct and underneath into the Coke shape.

And the floor has a curved foot ahead of the rear wheels,’ confirms Litjens.

While blanking plates are allowed to help with brake temperatures in cooler conditions, that is the only permissible change to the bodywork, so the whole cooling concept has to be geared for the hotter races.

Moving back through the car, the air intake above the roof is significantly set back compared to the TS050, and the fin on the engine cover is of totally different design. ‘The regulations in LMP1 said you had to start [the air intake] a few millimetres behind the windscreen, but it is not there any more so you are more free to work around,’ says Litjens. ‘The air inlet feeds the engine and the gearbox cooler, as well as our cooling to the exhaust.

‘The fin is not mandatory any more. You have the downforce and drag levels to respect to be in the [performance] window and then, because of the stability of the cars, there are some regulations set up with a reference car in CFD. They have to find certain ride heights and yaw angles, and you then have to make sure your car is better than the reference car.

‘We started off without any fin, and therefore have a double-pillar rear wing, but to fulfil the criteria, we know from LMP the shark fin is a big step. That is why we added a big part of it back in by development.’

The decision to try to build the car without the fin was again driven by the road car design. ‘We didn’t know what the road car would look like with the fin, so that’s why we started without, but we realised after the first check that it would not be clever [to leave it out],’ notes Litjens. Noticeably, and significantly, the rear wing end plates 10 Le Mans 2021 • Racecar Engineering

Nose of the car remains high, though the driver’s legs are actually lower in the chassis than they were in the previous TS050

are smaller than might be expected and the team did experiment with them, making them larger initially to compensate for the loss of the fin and there is still an option to adopt this concept within the homologation period if the design team can make it work.

‘Your homologation is for five years, but each manufacturer within these five years has the chance to do an update,’ confirms Litjens. ‘The good thing is that it was not planned to allow anything like that, but it depends which manufacturers come with their own programme. They kept it flexible with their newcomers and work with people’s road car programmes.’

Development path With a view to reducing costs, the new era of endurance racing’s top class will feature simpler cars, and with that has gone the interlinked suspension that was a feature of the old LMP1s. Designed to create a stable aero platform, the complicated and expensive system has been replaced with a traditional independent system on the four corners.

Also different is the braking system, which by regulation features a brake-by-wire system for the MGU-K at the front and, for the first time in Toyota’s WEC programme, a hydraulic system at the rear. The brake sizes on the TS050 were led by the amount of hybrid regen’ that could be harvested, but with this more conventional layout the brakes are of more traditional size.

The area with possibly the biggest development path is the electronics

The area with possibly the biggest development path is the electronics that will need to cope with the ever-changing demands on the brake pedal

that will need to cope with the everchanging demands on the brake pedal.

While the car is charging up the battery using kinetic energy under braking, the force on the pedal would be lighter than when the battery is fully charged and more braking requirement is needed.

‘It is a nice exercise for our people,’ says Litjens. ‘Either it is full conventional on both axles or not, so now we really have to find a way to control it in a smooth way.’

This has taken time to perfect with the drivers reporting that the car is tricky to manage on the brakes, but by Le Mans the team had completed its 24 hour test programme and was confident that it had addressed the issues. This is a learning exercise for all concerned, and it remains to be seen how much more development still needs to be done.

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ENDURANCE | GLICKENHAUS 007C HYPERCAR

Glick bait

The Glickenhaus 007C is a privately-funded Hypercar set to take on the factories in endurance racing’s greatest contest Frederik Herregods; Motul

By ANDREW COTTON

J

im Glickenhaus has taken the next step in his commitment to endurance racing and signed up to take a Hypercar to this year’s Le Mans 24 Hours, and compete in rounds of the FIA World Endurance Championship.

His 007C, a ground-up design that features a twin turbo V8 engine from Pipo Moteurs and a chassis from Podium Advanced Technologies, has competed in two of the first three rounds of the series and shown some serious signs of improvment.

12 Le Mans 2021 • Racecar Engineering

The team delayed the final homologation of the car until they were certain that it was right, as they did not believe that they should rush a design that would be fixed for five years. Therefore, they elected to miss the first race at Spa and instead focus on testing, particularly at Vallelunga and Monza where much of the pre-season mileage was undertaken.

The philosophy behind the programme is to sell cars rather than to compete for marketing value, and so the team is clear

that it will only contest the races that are important to its sales platform. It is unlikely that they will compete in Bahrain, for example, with the double header planned for November, as they do not expect cars to be sold on the back of a result. The golden races for the team are Le Mans, plus the Sebring event scheduled for March of next year, as well as the classic races including Spa and Monza.

The team has been immaculately prepared, with Podium Technologies

The 007C showed promising form so far, setting fastest lap at Le Mans in the pre-race test

designing and building the engine, Pipo Moteurs developing the engine, and Joest running the car.

The result has been that the cars have performed increasingly well, from a one-car effort at Portimao where tyre issues were combined with traction control problems and an accident, to Monza where two cars raced, to the Le Mans test day where the 007C model topped the timesheets. The car has the speed, but there is a lot of learning still to achieve before it can take on the big teams.

The story behind the development of the car has already been written about in REV30N8. The regulation changes to accommodate the power output levels demanded by Aston Martin’s wish to race the Valkyrie caused delays in the design and development process for Podium, and also meant Glickenhaus had to change engine manufacturer for the 007C. However, the basic rule set from the FIA has led to a pretty straightforward design.

With easily attainable aero figures to work to,

the company has been able to focus its efforts on styling, driver comfort and accessibility for the mechanics to work on the car.

In the nose, the design team was free of the constraints faced by Toyota, which had to package an MGU and driveshafts due to its hybrid design.

A problem of balance The aero is not challenging because the whole category is performance balanced.

Howewver, while the old LMP1 cars were Racecar Engineering • Le Mans 2021 13

ENDURANCE | GLICKENHAUS 007C HYPERCAR

Frederik Herregods; Motul

Though the 007C is not quite the ultimate road car cum racecar Glickenhaus imagined, its styling is consciously more closely related to a production car than a pure racing Prototype

capable of lapping Le Mans in sub 3m15s, these new cars have a target lap time of more than 3m25s in qualifying and race 12 seconds slower. That has put them directly into the old LMP2 car territory, so balancing the performance is not only about ensuring each of the Hypercars has a chance to win overall, but is also fast enough to beat the secondtier cars. The LMP2 cars have had power reduced and Goodyear was asked to produce slower tyres, but the teams and drivers were unhappy and so the performance windows of the Hypercars may yet change.

‘The way the balance of performance works, it is quite easy,’ says Luca Ciancetti, head of automotive engineering and motorsport business lines at Podium Advanced Technologies. ‘If you are slow you get power, and if you are fast you get weight. That is much simpler than reality because there are factors such as tyre degradation, fuel consumption and so on to take into account, but that’s the basics of it.’

Performance difference Already there have been changes to the basic Hypercar structure, with the Toyota given an extra 10kg, and Jim Glickenhaus believes that with its hybrid system, the GR010 will have better tyre wear on long runs.

Ciancetti does not believe that there will be a huge performance difference between the 007C and the Toyota GR010 over a single lap, though, as the power is limited between the two cars and monitored closely, while 14 Le Mans 2021 • Racecar Engineering

Accidents are a part of testing, and at Vallelunga the team’s first chassis was put through its paces against the barriers

Safety was also a prime consideration throughout the project because accidents can, and do, happen

Frederik Herregods; Motul

The aero on the car might look fairly benign, but there’s a lot more going on under the floor than meets the eye. That, says Luca Ciancetti, is a key factor in the car’s performance

The performance [targets] were not a huge challenge for us because once you are in the window, you are in the window Luca Ciancetti, head of automotive engineering and motorsport business lines at Podium Advanced Technologies

weight and weight distribution are also clearly defined by the regulations. What that means is the two will fight evenly for the honours in qualifying, but the Italian believes the outlier is the Alpine, the former LMP1 ORECA chassis raced by Rebellion. That car, powered by a Gibson engine, was designed to a different rule set capable of lapping Le Mans sub 3m20s in race conditions.

‘I have no idea what they will do with Alpine because we have no knowledge of that car,’ admits Ciancetti. ‘Toyota knows more than us because they had an LMP1 car so they can compare concepts, while we did not.’

That knowledge of a previous car could have been crucial in the design phase of the GR010, as Toyota had to scale back on its previous performance targets, while for Podium the Hypercar was a step up from the Glickenhaus 003C. The 003C is the car Glickenhaus races at the Nürburgring in the NLS championship (formerly the VLN), and which he hopes will be classed as a GT3 under new regulations due for 2023.

That car was also developed by Podium.

Window shopping

Pipo Moteurs provided the car’s V8 powerplant, which uses twin turbos to easily meet the performance targets for the class

‘The performance [targets] were not a huge challenge for us because once you are in the window, you are in the window,’ says Ciancetti.

‘We never found ourselves in a position where we were thinking we would not be able to get into the window. We had a feeling that it was not that difficult to get there.’

That allowed for some design freedom

in the car and the Podium team was able to stick pretty closely to Jim Glickenhaus’ original design concept. That is based on the old idea of being able to drive beautiful cars to the track and race them, and then drive home again. While the 007C will not be able to run on the road, there are clear styling cues that are closer to production cars than a prototype racer and that also left Podium with freedom in technical design.

Importance in design ‘From day one we really focused on giving more importance to the design of the suspension,’ says Ciancetti. ‘When you are designing the front of the car, one of the key choices is do I leave space for aero or can I optimise the suspension geometry and also have access to the suspension to make it easier to adjust? We understood it was better to have good suspension design with good access rather than leave a lot of room for aero that was really not needed.’

Driver comfort is important in a 24hour race and, again, the design of the cockpit was relatively straightforward.

Without the need for a hybrid system, and all the components to control it, there was room to create a cleaner, less cluttered environment in which to work.

With a higher minimum weight for the car, teams have been able to design the chassis with safety as a high priority.

The 007C passed its crash test set by the FIA in mid-March and, shortly afterwards, Racecar Engineering • Le Mans 2021 15

ENDURANCE | GLICKENHAUS 007C HYPERCAR

Driver safety Seating position is critical, not only for driver comfort but also for safety, and the Glickenhaus has a more upright seating position than the LMP1 cars before driven partly by different regulations. The driver’s legs are positioned lower in the chassis, which not only helps with driver visibility, but also means the shoulder straps take more force than the seat in the event of an accident, reducing the possibility of backbreaking accidents as were seen in LMP1.

‘If you were going for higher performance you probably would need to create some free volume for aero below the legs of the driver, but in our design the driver’s legs are quite flat with the main plan of the lower part of the chassis,’ confirms Ciancetti. ‘We could deal with that. With the additional design requirements you have to fulfil [with a

Photos: Frederik Herregods; Motul

on cold tyres, the prototype crashed at Vallelunga, without major damage as all parts performed as designed.

‘Again, I have to say the regulations do not give a lot of design freedom because so many of the parameters are set, including the minimum weight of the tub itself and also the position of the c of g,’ notes Ciancetti.

‘At the end of the day, you have to deal with the chassis design, but our chassis today for the Hypercar is a completely different world compared to the older one.

‘We don’t have the super fancy materials in it because then you will end up with something to live with that you don’t need. It is complex manufacturing and a complex construction, but it is not as difficult as it needed to be with an LMP1.’

Driver safety and comfort has always been high on the agends, and the end result is a low, more upright seating position

hybrid] it is easier and more straightforward if you don’t have that added complexity.’

In the discussion over the regulations, the change in engine outputs varied wildly, from more than 1000bhp (745kW)to today’s figure of 670bhp (500kW), comprised of either straight engine power as the Glickenhaus provides, or a combination of ICE and hybrid energy. Those negotiations affected the cooling requirements for the Glickenhaus design team, but not to a degree that caused massive concern.

Keeping cool ‘One key point is that you are not allowed to make any cooling personalisation, so the car is not allowed to be taped up or have a more refined way of reducing the amount of air

Without all the paraphernalia of a hybrid system to deal with, the driver compartment has been kept clean and uncluttered

A few pre-season words with Jim unless they have reliability issues. If they RE: You have said publicly that the LMH cars RE: You seem to have hit a sweet spot don’t, they will point blank be faster. will not be competitive in IMSA, and the with the fans in the pre-season with ‘We weigh the same, we are both pretty LMDh cars will not be quick in Europe. Why? your digital media results and openness robust, but they could run away from us. But I JG: ‘I said that until the day comes that with the technology you are using. think the ACO would be really unhappy if that fans believe an LMDh car could win the 24 JG: ‘It is tremendously pleasing. I don’t happened because I don’t think you can build Hours of Le Mans, and an LMH car can win understand the secrecy of everyone else. a better two-wheel drive, non-hybrid LMH car. the 24 hours of Daytona, you do not have Would I steal an idea from Toyota just because ‘I am not saying that Toyota they show me the underside of cannot build a car that’s slightly their car? It’s a joke. These cars are “The sanctioning bodies have to get honest. If they better, but it’s not an order of finished. They are spec’d and it’s a cannot find a way to have 100 per cent honesty and magnitude. Either we will be really BoP series. We have just been able to make our car a little prettier since a transparent BoP, the whole thing is meaningless” close, and they will have got it right, in which case it will come the aero isn’t that challenging. down to who makes the fewest mistakes, convergence and you do not have a believable ‘I don’t understand why they [Toyota] and do they have any reliability issues, or way forward. The sanctioning bodies have have gone hybrid, either. What’s the purpose? one of us will be a lot faster than the other. to get honest. If they cannot find a way to So that they can be seen to be green?

‘There was a fascinating photograph of our have 100 per cent honesty and a transparent The technology, and the money, and the cockpit and theirs, and there was 15 per cent BoP, the whole thing is meaningless. extra complexity to do it is just stupid. more crap in theirs because it’s all hybrid. The ‘They [the ACO] should have one set more electronics that you have in it, the more RE: So can you win races this year? of rules for convergence and these should chance you have that something will go amiss.’

JG: The Toyota is going to be the fastest, be the last of the ICE Prototypes.’

16 Le Mans 2021 • Racecar Engineering

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ENDURANCE | GLICKENHAUS 007C HYPERCAR going through the radiator,’ explains Ciancetti.

‘You therefore have to design a system that is able by itself to keep the working temperature of the engine in its proper range, and that means you have to work on the water cooling. That’s quite easy stuff because you set the dimension of the cooling system by working to the worst track condition – so the lowest circuit with the highest temperature – and, if you do that, you can still be in the drag target of the homologation.

‘It is tricky because we started the development of the car and the engine together, so we had to wait until we had the final figures for heat rejection from the engine. That affected the schedule of the programme, though, rather than the technical challenge.’

The car completed pre-season testing at Monza and Vallelunga, and showd the required pace. It’s shaping up to be a strong contender

Complex floor While the airflow looks to be relatively traditional, Podium developed a complex floor structure that is key to generating downforce. ‘We have a very complex floor and a very powerful flow,’ says the Italian.

‘We have a lot of air going under the car and it is a key performance factor. It was one of the most demanding elements to design.’

Right from the start, the team elected to go to the maximum length allowed by the regulations, but that meant rear stability might become an issue.

Although the bespoke gearbox from Xtrac was finalised early, as was the rear suspension, the whole aero package was the last part to be signed off.

‘We kept a lot of adjustability in the rear suspension in terms of damping and stiffness, but also geometry with the options we have,’

says Ciancetti. ‘With the rear wing it was a bit more tricky because the rear section of the car was the last bit we released for the aero, but now we have a good solution. That rear section is key for the performance of the car.’

Yaw stability Strakes on the rear wing are an unusual feature of the car, and the large rear wing end plates also suggest the team was looking for solutions to meet the stability at yaw angles stipulated by the FIA. While Toyota looked at designing its car without the fin over the engine cover, and Jim Glickenhaus

hoped for the same, Podium decided that the fin was the most efficient solution.

‘The reason for that solution [the rear wing] is the lateral stability of the car,’ confirms Ciancetti. ‘You have to demonstrate that your car is safe enough in lateral stability and, due to the shape of our car – due to some design choices we have a long car – it is much more difficult to achieve that. We had to add vertical fins.

‘As already mentioned, as long as you are in the performance window you are fine.

We have our hot spots in that window, and we are where we chose to be.’

Like the Toyota GR010 it will race against, the 007C features a pronounced dorsal fin to meet the FIA’s mandated yaw stability requirements, as well as vertical strakes on the rear wing

We have a lot of air going under the car and it is a key performance factor. It was one of the most demanding elements to design 18 Le Mans 2021 • Racecar Engineering

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10:01

BALANCE OF PERFORMANCE | WEC

The layout of the LMH cars is tightly controlled. A minimum weight for the engine and gearbox is prescribed, as is the centre of gravity in order to keep cars within the performance windows. Pictured is the Glickenhaus in build

Small torque The FIA and ACO are looking to balance different concepts with their top class for the WEC. Prior to their introduction on track, we sat down with the architect of the rule set to find out how they work

By ANDREW COTTON 20 Le Mans 2021 • Racecar Engineering

We’re ensuring sporting equality and preventing cost escalation Gilles Simon, former FIA technical director

T

he new era of Prototype racing at Le Mans and in the World Endurance Championship has begun, with the Le Mans Hypercar (LMH) class governed by an ambitious performance balancing system devised using the latest technology.

This is a change in concept from the LMP1 era, where equivalence of technology balanced the cars. The issue with this was each car had to perform at its maximum capability in order to achieve the efficiency needed to be competitive. That was expensive and so, for the Hypercar era, a more invasive and prescriptive performance balancing system has been devised by

the technical teams at the ACO and FIA. Designed to allow for different concepts to race on an equal basis, it also aims to remove the incentive to develop any part of the car for performance gain.

Evaluation process Following a long evaluation process, the LMH class comprises five different routes into the Le Mans Hypercar category: hybrid Prototypes; non-hybrid Prototypes; hybrid road cars; non-hybrid road cars, and LMDh, which is based on an homologated chassis built by LMP2 manufacturers with a standard hybrid system and engines and aero kits chosen by the OEM.

In order to bring these different concepts into the same performance bracket, parameters have been set to govern power, weight and aerodynamic efficiency, and manufacturers have to design their cars to meet these targets. They are designed against a virtual ‘reference’ car that has been created by the FIA and ACO technical teams in CAD and meshing to test and develop the new aerodynamic regulations.

The manufacturers do not necessarily measure themselves against this car, but can use it as a calibration reference to re-scale their development tools, especially CFD. It is against this reference car that Toyota measured its yaw stability without the fin Racecar Engineering • Le Mans 2021 21

BALANCE OF PERFORMANCE | WEC

Power struggle

Engine speed POWER (kW) Engine speed POWER (kW) (N/Nmax) POWER 500(kW) Engine speed (N/Nmax) 500 0.550 246 (N/Nmax) 500 0.550 246

PowerTrain Power PowerTrain Power Referenced to 1010 mbar and 20°C PowerTrain Power Referenced to 1010 mbar and 20°C

550 550 550

Referenced to 1010 mbar and 20°C

Power Power Power Output Output Output @Wheels @Wheels @Wheels (kW) (kW) (kW)

500 500 500 450 450 450 400 400 400

350 350 350

Engine Speed (N/Nmax) Engine Speed (N/Nmax)

269 246 269 289 269 289 309 289 309 330 309 330 351 330 351 372 351 372 393 372 393 413 393 413 432 413 432 449 432 449 464 449 464 475 464 475 485 475 485 492 485 492 497 492 497 500 497 500 498 500 498 495 498 495 427 495 427 427

236 LOW 236 258 236 258 277 258 277 297 277 297 317 297 317 337 317 337 358 337 358 378 358 378 397 378 397 415 397 415 431 415 431 445 431 445 456 445 456 466 456 466 472 466 472 477 472 477 480 477 480 478 480 478 475 478 475 410 475 410 410

256 HIGH 256 279 256 279 300 279 300 322 300 322 343 322 343 365 343 365 387 365 387 409 387 409 430 409 430 449 430 449 467 449 467 482 467 482 494 482 494 505 494 505 512 505 512 517 512 517 520 517 520 518 520 518 514 518 514 444 514 444 444

Pref = 1010 mbar, Tref = 20°C Pref = 1010 mbar, Tref = 20°C Patmo (Atmospheric Pressure in mbar), Tatmo (Atmospheric Temperature in °C), Hatmo (Atmospheric relative Humidity in %) Pref = 1010 mbar, Tref = 20°C Patmo (Atmospheric Pressure in mbar), Tatmo (Atmospheric Temperature in °C), Hatmo (Atmospheric relative Humidity in %) Patmo⎡(Atmospheric Pressure in mbar), Tatmo (Atmospheric Temperature in °C), Hatmo (Atmospheric relative Humidity in %) ⎤ ⎡⎢ ⎤⎥ ⎢⎡⎢ ⎥⎤⎥ 1 ⎢ ⎥⎥ 1 𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 ⎢⎢1; O.OPQ 𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 ⎢1; ⎥⎥ 1 O.OPQ ⎧ ⎫ ⎢ 𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 ⎢1; ⎧ (𝑇𝑇𝑇𝑇𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑚𝑚𝑚𝑚𝑃𝑃𝑃𝑃 + 273)⎫⎥⎥ 𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 NO.OPQ ∗ (𝑇𝑇𝑇𝑇𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑚𝑚𝑚𝑚𝑃𝑃𝑃𝑃 + 273) ⎥ ⎢ ⎧, 𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 𝑇𝑇𝑇𝑇𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑚𝑚𝑚𝑚𝑃𝑃𝑃𝑃 𝐻𝐻𝐻𝐻𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑚𝑚𝑚𝑚𝑃𝑃𝑃𝑃 N 𝑇𝑇𝑇𝑇𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑚𝑚𝑚𝑚𝑃𝑃𝑃𝑃 (𝑇𝑇𝑇𝑇𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 + 273) ⎫ ⎢ ⎨, ⎥ ∗ (𝑇𝑇𝑇𝑇𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 66.1121 ∗ 𝑃𝑃𝑃𝑃𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒 =>18.678 − 𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 𝑚𝑚𝑚𝑚𝑃𝑃𝑃𝑃++273) 273)⎬ 𝑇𝑇𝑇𝑇𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 𝑚𝑚𝑚𝑚𝑃𝑃𝑃𝑃 E ∗ (257.14 𝑇𝑇𝑇𝑇𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃+𝑚𝑚𝑚𝑚𝑇𝑇𝑇𝑇𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 𝑃𝑃𝑃𝑃 𝑚𝑚𝑚𝑚𝑃𝑃𝑃𝑃) I ∗ 𝐻𝐻𝐻𝐻𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 𝑚𝑚𝑚𝑚𝑃𝑃𝑃𝑃 LM (𝑇𝑇𝑇𝑇𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 ⎢⎣ ⎨,1𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑚𝑚𝑚𝑚𝑃𝑃𝑃𝑃 − 66.1121 ⎬⎥⎦ 234.5 100 ∗ E∗ LMN I ∗ 𝐻𝐻𝐻𝐻𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 ∗ 𝑃𝑃𝑃𝑃𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒 =>18.678 − 𝑇𝑇𝑇𝑇𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 ⎩ 1𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑚𝑚𝑚𝑚𝑃𝑃𝑃𝑃 − ⎭ 𝑚𝑚𝑚𝑚 𝑃𝑃𝑃𝑃 𝑇𝑇𝑇𝑇𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 𝑚𝑚𝑚𝑚 𝑃𝑃𝑃𝑃 𝑚𝑚𝑚𝑚 𝑃𝑃𝑃𝑃 (𝑇𝑇𝑇𝑇𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 + 273) (257.14 234.5 100 + 𝑇𝑇𝑇𝑇𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 𝑚𝑚𝑚𝑚 𝑃𝑃𝑃𝑃) ⎣⎢ ⎩ ⎭ ⎨ 1𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑚𝑚𝑚𝑚𝑃𝑃𝑃𝑃 − 66.1121 ∗ 𝑃𝑃𝑃𝑃𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒 =>18.678 − ⎬⎦⎥ E∗ LM I (257.14 + 𝑇𝑇𝑇𝑇𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑚𝑚𝑚𝑚𝑃𝑃𝑃𝑃) ∗ 100 234.5 ⎣ ⎩ ⎭⎦

Power Unit usage is free (settings, modes) as far as the total power stays below the maximum power limit allocated by the BoP. Power Unit usage is free (settings, modes) as far as the total power stays below the maximum power limit allocated by the BoP. Power Unit usage is free (settings, modes) as far as the total power stays below the maximum power limit allocated by the BoP. The shape of power delivery is also strictly controlled. There is a maximum peak power figure of 500kW, with penalties issued during the race if that target is exceeded

on the engine cover, for example, and when it was unable to meet the technical team’s requirements, it reverted back to the fin.

Philosophy changes The LMH category has had to make some changes to its philosophy in order to achieve the desired performance balance, one of which is to specify a single tyre supplier, Michelin. However, the French company is able to develop tyres specific to two-wheeldrive cars (29/71-18 front, 34/71-18 rear with narrower front wheels) and four-wheel drive cars (31/71-18 front and 31/17-18 rears).

In order to meet the targets, the FIA has had to be prescriptive with its design parameters for the LMH cars (the LMDh cars follow different design rules), including a minimum weight and c of g for the engine (165kg and no less than 220mm above the 22 Le Mans 2021 • Racecar Engineering

reference plane) and gearbox (75kg and 150mm above the reference plane). Weight distribution is homologated for each car with a small tolerance, which will avoid manufacturers playing with extreme weight distribution change between events.

‘The application of the principle of ‘performance windows’ is a completely new regulatory approach by the FIA and the ACO to the top class of the FIA World Endurance Championship,’ said the FIA’s former technical director, Gilles Simon when interviewed pre-season. ‘This way we’re ensuring sporting equality and preventing cost escalation. It has been made possible by the application of a precise and modern methodology for measuring first order performance parameters, combined with the experience of efficient data acquisition and analyses processes.’

Weight distribution is homologated for each car with a small tolerance, which will avoid manufacturers playing with extreme changes between events

CMSA / WMSC 16.12.2020 Publié le / Published on 16.12.2020

Details: Details: The PU performance may be checked on a dyno, and homologated. It will include: Details: The PU performance may be checked on a dyno, and homologated. It will include: - performance Power vs rpm. expected power below 0.55xNmax is lower than 246 kW. The PU may It beis onthat a dyno, and homologated.

It will include: Power vs rpm.

It ischecked expected that power below 0.55xNmax is lower than 246 kW. Maximum rpm.It is expected that power below 0.55xNmax is lower than 246 kW. --Power vs rpm.

Maximum rpm.

Maximum rpm.

The maximum power is given for reference conditions: 1010 mbar 20°C and 0 % Relative Humidity.

The maximum power is given for reference conditions: 1010 mbar 20°C and 0 % Relative Humidity.

If themaximum ambient conditions naturally reduce conditions: performance, thembar maximum power willHumidity. be corrected, at the beginning of each event, to the The is given for reference 1010 20°C and 0 % curve Relative If the ambient power conditions naturally reduce performance, the maximum power curve will be corrected, at the beginning of each event, to the ambient conditions using the following correction factor: the maximum power curve will be corrected, at the beginning of each event, to the If the ambient conditions naturally reduce performance, ambient conditions using the following correction factor: ambient conditions using the following correction factor:

90/96

500 500 kW 500 kW 300 kW 480 300 480 kW 300 480 kW 250 kW 520 250 520 kW 250 520 kW 200 kW 2000.550 0.575 0.600 0.625 0.650 0.675 0.700 0.725 0.750 0.775 0.800 0.825 0.850 0.875 0.900 0.925 0.950 0.975 1.000 1.025 2000.550 0.575 0.600 0.625 0.650 0.675 0.700 0.725 0.750 0.775 0.800 0.825 0.850 0.875 0.900 0.925 0.950 0.975 1.000 1.025 Speed (N/Nmax) 0.550 0.575 0.600 0.625 0.650 0.675 0.700 0.725 Engine 0.750 0.775 0.800 0.825 0.850 0.875 0.900 0.925 0.950 0.975 1.000 1.025

0.575 0.550 0.575 0.600 0.575 0.600 0.625 0.600 0.625 0.650 0.625 0.650 0.675 0.650 0.675 0.700 0.675 0.700 0.725 0.700 0.725 0.750 0.725 0.750 0.775 0.750 0.775 0.800 0.775 0.800 0.825 0.800 0.825 0.850 0.825 0.850 0.875 0.850 0.875 0.900 0.875 0.900 0.925 0.900 0.925 0.950 0.925 0.950 0.975 0.950 0.975 1.000 0.975 1.000 1.025 1.000 1.025 1.025

ADJUSTMENT (kW) ADJUSTMENT (kW) LOW HIGH ADJUSTMENT (kW) LOW HIGH

© FIA/ACO

Cars must be designed to target the following total maximum power curve (Sum of the 4 wheels power measured by driveshaft torque sensors) Cars must be designed to target the following total maximum power curve (Sum of the 4 wheels power measured by driveshaft torque sensors) with must low and margins to be the adjusted for BoP reasons as follows: Cars be high designed to target following total maximum power curve (Sum of the 4 wheels power measured by driveshaft torque sensors) with low and high margins to be adjusted for BoP reasons as follows: with low and high margins to be adjusted for BoP reasons as follows:

© FIA/ACO

© FIA/ACO

The mechanism for power delivery is also prescribed, and the front wheel hybrid unit will only be able to replace power from the engine, not add to it

Order of play

90/96

The first order parameters are the targets for the car designers but, traditionally, the trouble starts with second and third order consequences. Topics such as tyre wear, pitch sensitivity and cornering are only able to be studied in track conditions, and for these to be made accurate, mileage needs to be accumulated.

Toyota has targeted four stints at Le Mans and double stinting tyres in a regular WEC race, while Glickenhaus believes it is at a disadvantage as it did not complete the same mileage pre-season, and its tyres are not nearly as developed as its rival. However, it does have the advantage that its tyres will form the basis of the LMDh rubber, and so has Michelin’s full development support.

ByKolles and Peugeot, meanwhile, are not due to release their cars until

90/96

2022 or 2023, and LMDh cars are still in the design phase, with their introduction date yet to be confirmed.

However, the definitive answer to questions over such issues as tyre longevity is not yet made, and with pre-season testing disrupted or delayed due to weather (Toyota’s test at Aragon in January was disrupted by snow) and Covid-related travel restrictions, they probably won’t be until the tail end of the 2021 season.

The need to test pre-season was all the more critical this year as the homologation period for the cars has been set at five years, with no performance development allowed in that time. The only changes allowed are for reliability, and only with the advance permission of the FIA. There is a caveat though, and teams are able to build one update within the five-year

homologation period, which could play into the hands of Toyota which could bring an entirely new car, although Glickenhaus is unlikely to make that same investment.

Performance target ‘The targets of BoP are to make sure every car has the chance to win a race,’ says Simon.

‘Hypercar has a much closer starting point than the LM GTE class, yet we managed to balance out different LM GTE cars and have extremely close level of competition. They all had the chance to compete on equal terms.

‘In the Hypercar category, all the cars are designed for racing. Overall race performance, stint length and refuelling time are part of the BoP process and therefore equalised.’

Traditionally, over time BoP racing reduces the performance differential Racecar Engineering • Le Mans 2021 23

BALANCE OF PERFORMANCE | WEC

The LMDh cars will use a spec hybrid unit and are performance balanced up to LMH pace, which for a chassis and running gear that was originally targeted at the customer market in LMP2 will be a significant shift in focus

between the cars. Development costs drop due to long homologation periods and penalties for improving performance, though costs start to escalate again as car designers delve deeper into the systems available to extract any small advantage. However, live telemetry readings and detailed lap analysis attempt to stave off that threat.

‘We are constantly developing the BoP, measuring more parameters and ensuring it’s tailor made to the requirements of each category,’ says Simon. ‘The FIA and the ACO have a wealth of experience to lean on as BoP has been in use since the mid-2000s, and each year there are over 40 FIA-regulated events where BoP is employed, varying from crosscountry to Touring Cars and GTs.’

GTE experience The system is a variation on that used for the GTE category which, in the World Endurance Championship, is governed autonomously.

The category allows manufacturers to race production-based cars with different layouts, but was decided by humans using available data. An automated system was developed in association with the manufacturers.

24 Le Mans 2021 • Racecar Engineering

This takes the performance of the cars in a given circumstance, with a sustained and measured period of dry running in the previous race, and then balances them for the next event. Only Le Mans sits outside the automated system due to its unique circuit layout and 24-hour duration.

For the rest of the WEC season the arguments have now stopped, partly due to the involvement of manufacturers in the process, which left them little room to criticise their own system, but also because it has produced close and competitive racing. Manufacturers have also found they cannot rely on the system to make up for performance deficiency.

Entry point As satisfactory as the GTE system is, the entry point into the automated BoP was key to its success. Given the length of time between races, and the fact that the majority of them feature at least some wet weather running, if a car had the wrong initial settings, it could take the rest of the season to correct it.

For the Hypercar category, with overall wins at stake, that entry point will be even more crucial, but the FIA is confident it will have enough knowledge of the cars

The FIA and the ACO have a wealth of experience to lean on as BoP has been in use since the mid-2000s to be able to balance them. ‘LM GTE was an important experience for us,’ confirms Simon. ‘However, the Hypercar BoP will be different, owing to narrow aero performance windows and the introduction of a brand new torque meter sensor, developed specifically for the Hypercar category.

‘The three first-order performance parameters, weight, power and aero, are the same for all the cars. The entry point [into the BoP system] will be defined automatically, based on homologation data including wind tunnel data, weight, propulsion type, two and four-wheel drive and fuel consumption.

This is new compared to LM GTE, but the homologation procedure is now gathering more performance data to achieve a narrower performance estimation target, owing to the introduction of the new tools.’

Unlike GTE, there is only one body kit homologated for the season, which will reduce the downforce on many of the circuits as the traditionally low-drag Le Mans kit is likely to take priority. Only blanking for the brakes are allowed as a safety measure.

‘As there’s now only one aerodynamic bodywork, no sprint and Le Mans kit any more, the Le Mans Hypercars will stay the same in all types of races, so consistency will be better on all tracks,’ confirms Simon.

Torque meters Torque meters at the driveshaft are nothing new. Indeed, GT3 looked to bring them in as part of its performance balancing process, but discounted the idea as too expensive for a customer-based programme. They also generate a huge amount of data that needs to be considered in real time, which is not cheap, and their physical size means it is not a question of simply bolting them on.

‘Three types of data will be used to control the performance,’ says Simon.

‘We will have homologation data, which is the measurements coming from the wind tunnel, tyre data, weight and hybrid specification. We will also have timing, which includes split times and GPS, and we have the data from car sensors connected to the FIA / ACO data logger. They will include the torque meter, fuel flow meter, speed, attitude of the car and driver commands, including braking, steering and acceleration.

‘The FIA and the ACO have developed specific tools able to manage these three types of data, all of which will be

correlated and augmented with simulation tools.’ As the data will be recorded live, the technical team is confident there will be no delay in analysis that might cause a race result to be compromised.

In the regulations there is a list of penalties that may be applied should any car breach the performance targets mid-race. Any such penalties will be served during the race.

Everything that has an absolute limit causes teams a headache as they have to get as close to that limit as possible without breaching it. It’s a different philosophy to the old LMP1 era, and the WEC technical team also understands that racecars have a habit of being unpredictable. Power is limited to 500kW, for example, but there may be occasions when the software is milliseconds too slow to react and that limit is exceeded. So how stringent are these regulations and penalties?

Zero tolerance ‘The aerodynamic performance window is set for homologation only,’ confirms Simon.

‘It’s fixed, and to be homologated a car must be in the performance window when measured in the wind tunnel. No tolerance is allowed. Basically, the car will race in that exact configuration, and bodywork scanning will be performed to check this.

‘During the event, the BoP is enforced with ballast and power fixed. There is no tolerance on minimum weight, as with other categories. There’s no tolerance on maximum power, which is controlled live by

The three first-order performance parameters: weight, power and aero, are the same for all the cars the torque meters, and there is an appendix in the Sporting Regulations that provide for some of the BoP abuse penalties.’

Aero measurements take place at the Sauber wind tunnel in Switzerland, where much of the GTE aero work is undertaken.

The information is solely for the FIA and ACO technical teams, and is not shared with Sauber personnel or with other teams and manufacturers. Teams also conduct much of their testing there to comply with FIA demands when it comes to actual testing.

‘We have defined a process to compute the exact position in the performance window [CdA/ClA],’ says Simon. ‘Once the car is in that window, the bodywork, including blanking and all movable aero devices, is frozen, 3D scanned at the FIA and homologated. During an event, we check that the bodywork, and any other elements that influence aerodynamic performance, is exactly the same as the one measured in the wind tunnel as there is a scanning process at scrutineering.

Peugeot will join Toyota and Glickenhaus in Hypercar as will ByKolles. Audi, Porsche and Acura are coming with LMDhspecification cars. Others are expected to announce programmes, with Ferrari and Hyundai favourites to do so

Racecar Engineering • Le Mans 2021 25

BALANCE OF PERFORMANCE | WEC

Toyota introduced a first version of its Hypercar at Le Mans. This is the roadgoing model on which the Prototype will be based.

Toyota Gazoo Europe has been developing the car in line with the Le Mans variant

‘Aerodynamic performance will also be monitored on track with top speed correlation and suspension sensors. But this is more for understanding and knowledge to improve the process in the next years.’

Although there will be a five-year homologation cycle, there will be an opportunity to update a Hypercar when new manufacturers join. However, this is not the same as a ‘joker’ package that is permitted in LMP2. There, any manufacturer with a performance deficit, or with a need to make a change, is permitted to do so in order to close the gap. ‘No ‘joker’ package is needed here because the championship is ruled by a BoP,’ insists the Frenchman. ‘Any possible difference will be compensated by a different combination of ballast, power and any other necessary measures.’

Bumpy road From the manufacturers’ point of view, the BoP windows are a design target, but even within them there is an issue that needs to be considered. With the four categories stipulated by the FIA and ACO, there is also the LMDh route into the series.

The LMDh set of regulations is essentially IMSA’s DPi regulations updated, or at least that was supposed to be the plan. The DPi rule set was based on the existing LMP2 chassis, then fitted with an OEM engine and bodywork. The LMDh class was supposed 26 Le Mans 2021 • Racecar Engineering

to follow this same formula but the FIA and ACO had delayed the introduction of the Hypercar regulations to such an extent that they have not yet even thought about LMP2. No technical regulations have been issued, and no tender for the engine has even been submitted to interested parties.

Therefore, the LMDh chassis is not based on the LMP2 design as there isn’t one. OEMs are therefore free to design their own chassis to build by one of the four selected LMP2 chassis manufacturers, namely ORECA, Multimatic, Ligier and Dallara. The LMDh car will feature LMP2 style running gear, including the gearbox from Xtrac, plus a standard hybrid system alongside engine and bodywork stipulated by the manufacturer.

‘A significant job has been achieved to allow competition between LMH and LMDh,’ says Simon. ‘Aerodynamic performance window, minimum weight and maximum power are identical. That was the key target to achieve convergence between the two types of cars. It was in the interest of all parties, and especially the manufacturers, to achieve this global target for endurance racing.

‘Furthermore, all the homologation process will be identical and done in a transparent collaboration manner.

‘It’s also important to note that LMH can choose between two different dimensions of tyres, and use the most

It is now up to the race and technical teams to turn it into a competitive and fair system suitable option [linked to car architecture and weight distribution]. In LMDh, all the cars will be in the same window of weight distribution and will be allowed to use only one tyre dimension option.’

Clearly, the FIA and ACO technical teams have thought through the process and spent years fine-tuning the concept throughout the discussion phase. However, in practice balancing the different cars is not going to be easy or straightforward.

Given the different characteristics each will display, coupled with driving styles and team management, it will undoubtedly take a number of races to iron out the performance differences between the cars.

However, to have achieved a system by which manufacturers are able to commit to Le Mans’ top category is commendable. It is now up to the race and technical teams to turn it into a competitive and fair system.

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WEC | TYRE DEVELOPMENT

Photo: XPB

Two steps beyond

Michelin and Goodyear have sliced up the FIA World Endurance Championship and become sole tyre suppliers to individual classes within it, but with very different targets

By Andrew Cotton 28 Le Mans 2021 • Racecar Engineering

Racecar Engineering • Le Mans 2021

29

WEC | TYRE DEVELOPMENT

Photo: XPB

T

he FIA has continued its path to reduce competition in the face of cost control measures and in the FIA WEC awarded Michelin the Hypercar tyre deal, while Goodyear was granted the LMP2 sole supplier contract.

Naturally, both manufacturers have been tasked with providing tyres that fit the FIA’s performance targets and while Michelin has a parameter for Hypercar that is all new, Goodyear has been given the job of coming out of open competition and running tyres significantly slower than in 2020.

The criteria was laid out in the tender and both companies submitted bids, but the manufacturers on which the FIA increasingly relies insisted Michelin be awarded Hypercar, while Goodyear provides tyres for the customer racing LMP2 class.

With both tyre makers secure for three years and an option for a further two, the sands have shifted slightly under the feet of the rule makers as the Hypercars made their debut at Spa early in May and tyre peformance was one of issues.

Michelin’s task has not been easy, developing a tyre for a car that, until late on in 2020, did not exist. Under the original tender, tyres developed for the first race would have to suffice for the last race of the 2025 season but, with the deal safely secured, the tyre company now has three defined stages of development, and can enact them when it chooses.

Michelin’s Hypercar tyre is a cross between a GT construction to handle the weight, and a Prototype compound for performance. Despite the homologation being fixed, it has room to change

‘You don’t get a one size fits all anywhere, but especially in motorsport’

Photo: XPB

Matthieu Bonardel, Michelin

Alpine ran the ORECA Gibson previously campaigned by Rebellion and asked that the tyres be kept the same. Luckily, the car’s characteristics remain similar

30 Le Mans 2021 • Racecar Engineering

Caption The Toyota GR010 is heavier, slower and less powerful than the TS050 that it replaces, meaning tyre development for this season was extensive. Michelin took a conservative approach for year one.

There is a further complication, though, in that the LMH hybrids are four-wheel drive, while the Glickenhaus that will debut at Portimao in June will be rear-wheel drive, and the tyres on the 007C will be similar to the ones used for LMDh, which will be used in the Hypercar class in the WEC, and the top class in IMSA in the US.

Digital development ‘What has been really new in this adventure is the short lead time and a paper describing the specification of the car,’ highlights Michelin’s Matthieu Bonardel. ‘Pretty much all of [our development] was done through digital with simulation. We had the input from machine testing, and then iterations coming back from Toyota and from Glickenhaus. They would go for a test and then come back with new parameters and we had to adapt the tyre to that.

‘In the end, we came up with the fact that we are being asked to provide two different types of sizes, one for cars that would be centred, so half and half front and

rear axle, which is where one would expect four-wheel drive would be, and another for weight distribution that is more appropriate for rear-wheel drive, so more weight on the back. This made two families of tyres.’

The way in which the tyres work is totally different to those of the LMP1 hybrids.

They had around 500bhp from the ICE, and a further 500bhp from the hybrid system delivering power primarily to the front wheels. Under Hypercar regulations, the maximum total power output is 520kW, regardless of whether the power comes from ICE or a combination of ICE and hybrid, at Spa power was able to be delivered to the front axle only above 130km/h.

One size doesn’t fit all ‘It is more complicated because you don’t get a one size fits all anywhere, but especially in motorsport,’ says Bonardel. ‘You don’t have enough downforce where you want it, which is the low-speed tracks, so the tyre slides and wear and heat increases. Then, when you don’t want the downforce, like [at]

Monza and Le Mans, you get significantly more downforce than you need, which then causes more stress on the tyres.

‘In the end, you end up with wishing lower downforce here, and higher downforce there, but no, on the highspeed track it will get too much load.

‘People say the cars have less power and are heavier, and it should be easier on the tyre, but it is not. It is 40-50 per cent harder in the rear than with the previous generation because of the weight and downforce and the extra power, and the top speed will not be that different.

‘We are reasonably confident we will have things under control at Le Mans. We say we are not going to shoot for five stints this year, but we are confident for two stints. We have to see at the test day if we can go beyond two.

‘The reason we are in wait and see mode is because we want real data from real cars on track. Now, we are now dealing with prediction and the regulations are changing.’

The extra weight of the new generation cars and the limitations on Racecar Engineering • Le Mans 2021 31

Photo: XPB

The manufacturers on which the FIA increasingly relies insisted Michelin be awarded Hypercar, while Goodyear provides tyres for the customer racing LMP2 class

WEC | TYRE DEVELOPMENT

Photo: WEC

cooling due to the single aero package means the tyres must necessarily run hotter, and be designed to do so.

‘It is a different load and so the profile has to be adjusted to cope with that load,’ confirms Bonardel. ‘Then there is significant change in compound to tune them to the front and the rear of the car, and the fact that it shifted in terms of temperature. More weight equals more heat and so, compared to the previous Prototype, we are roughly 20degC hotter.

‘For sure, we are moving closer to the territory of the heat of GT with a signature that is closer to a Prototype.

Luckily, because we are in both categories, we can combine our knowledge.

‘The temperature is dictated by the weight and downforce of the car, and there is not much they can do to change that.

The centre of mass and weight of the car is similar, or with slightly higher camber to counter the roll. This is not unusual for GT, but is unusual for a Prototype.’

Changing the tyre through the five-year window means Michelin will be able to adjust first for safety and then, after that, bring in new, more environmentally friendly techniques in the construction of the tyre to help deliver a marketing message..

‘One of the advantages of being the sole tyre supplier is I can do what I want, with justification,’ adds Bonardel. ‘If I need to change it, I can. Even if we don’t have to change the tyres because there is a performance or safety reason to do so, we still have the plan to change it for next year.

‘If I can go five stints at Le Mans then we might reconsider, but it is the plan to change it next year to tune it to more longevity and less wear, and we want it to be a nice place to showcase innovation and anything that is in the spirit of sustainability.

‘That could mean using the tyre for more stints, it could mean more resistance to punctures, it could be to facilitate heat up to avoid needing tyre warmers, or it could be to introduce bio-sourced or recycled material.

In Moto-e we put bio-sourced and some recycled carbon back, so we are developing some kind of knowledge in race conditions.

The ACO and the FIA want us to do that.’

‘People say the cars have less power and are heavier, and it should be easier on the tyre, but it is not. It is 40-50 per cent harder in the rear than with the previous generation’ Matthieu Bonardel, Michelin

New blood One of the big changes coming is the introduction of new manufacturers with different cars. Peugeot will join the grid in 2022, and Ferrari in 2023, along with the LMDh cars from Porsche and Audi. Will they receive individually spec’d tyres, or will the two families of tyre technology suffice?

‘If they are in the same window of weight and balance then they have the same tyres,’ states Bonardel. ‘If they have something that is significantly different, then we say we are not going to have the same. This is the reason Glickenhaus has a different tyre.

They have a different signature [and] they have a heavier car, it is two-wheel drive.

‘The Alpine is grandfathered. They asked that we don’t mess up the car, give them the same tyre as when they were Rebellion. But we had to say you remove power and add weight, so it is a different

car. Luckily, the different things compensate.

Less power is less heat, more weight is more heat, and they put more weight in the front, so they are happy with their car.

We said okay, let’s not make it difficult.’

Unfinished business The tyres for the Glickenhaus 007C are different sizes to anything Michelin has produced before. Like the Hypercar itself, they were developed in CFD first, and are now on track with a heavy development programme.

‘The front and rear are brand new, and we have no experience,’ confirms Bonardel.

‘I am glad Jim [Glickenhaus] was happy with the mileage driven, but we are not.

We had one test session where they were limited. Our experience with the new front and new rear, and all the compound, we are much more at ease with the Toyota.

Goodyear has the LMP2 tyre contract for three years, with an option on a further two, and hopes it can then break into the Hypercar market with its range 32 Le Mans 2021 • Racecar Engineering

Photo: XPB

The United Autosport team dominated LMP2 at Spa, and was a threat to the Hypercars, despite measures to slow the cars in the lower category that included bringing a slower tyre to the class

‘They were not able to do long runs from day one. They have to fix electronics and things like that. It is a new car, so I don’t even know from a pace standpoint if we are able to do some of the things we would like. The development is not finished with this type of tyre.

‘It is very important because the front and rear tyre sizes will be the basis of LMDh. This is why I am taking everything that I can learn from this project because very soon Porsche and Audi will want this tyre, and I will have to make another decision. Is it the same tyre as Glickenhaus? Can I use the same mould, or do I need another one?’

Michelin is aiming to maintain the same technology for all its tyres, and allow the FIA and ACO to balance the performance of the cars using the tools at their disposal.

Total change The Hypercars are due to lose around 15 seconds per lap at Le Mans, making them

‘We did the first test in February 2020, targeting a two second drop in lap time compared to the 2019 LMP2 time, just in tyre development’ Mike McGregor, programme manager at Goodyear

a rating sheet that we work to where five is our baseline, 10 is better, and zero is worse,’ says Goodyear’s programme manager, Mike McGregor. ‘All of a sudden, when you’re doing a tyre performance drop, it’s hard then to speak to the drivers to get them to understand how you’re trying to write a product, to score it to move forward in that direction.’

Testing times Mike McGregor (left) led the Goodyear team to develop tyres to fit the FIA’s criteria

slower than the LMP2 cars’ lap times in 2020, which led to the inevitable conclusion that the latter would need performance restrictions ahead of the 2021 season.

The FIA and ACO therefore added 20kg to their base weight, the maximum that could be applied without the need for further crash testing, mandated a 50kW reduction in engine performance, a single, low-downforce aero package specifically designed for Le Mans and a slower tyre from Goodyear. In all, these changes were supposed to add up to a 10-second reduction in lap time at Le Mans, leaving still at least five seconds between the Hypercar and LMP2 categories.

For Goodyear, designing a tyre that is supposed to make up two of those seconds at Le Mans required a total change in thinking. Normally, tyres could be compared like for like, but in this scenario it was more a question of bad, or worse?

‘What we’ve done previously is have

That was to be the scenario once the tyre manufacturer got to the track, and circuits have been booked and paid for, but the ongoing Covid pandemic means they have simply not been able to get cars and tyres to the circuits as planned.

‘We did the first test in February 2020, targeting a two second drop in lap time compared to the 2019 LMP2 time, just in tyre development,’ recalls McGregor, ‘but then Covid hit. We had 15 tests booked between then and November, which is when we actually had the second test. With lockdown, and the changing schedules, either cars weren’t available, or circuits weren’t ready.’

The team had multiple back-up plans and had worked hard on simulations but, with a shortened timeframe testing on track, had its work cut out just trying to produce enough tyres for a full LMP2 grid for the entire season. Consequently, tests with cars from multiple teams were conducted, with all of the tyres developed during the lockdown, before a decision on which to use was taken.

‘From when we did the first test to November, we had varying levels of Racecar Engineering • Le Mans 2021 33

WEC | TYRE DEVELOPMENT performances within the tyres,’ says McGregor.

‘I think the big thing we noticed at the tests later in the year was how resilient and how good the ORECA is. The aero performance window of that car is phenomenal. We tried varying stiffnesses of the casings, up to 25-30 per cent, which, in terms of putting you in a timeline of Prototype tyres, we haven’t run tyres that soft since 2005.

‘It was to make the driveability easier for the [amateur] driver, and that little bit harder for the professional driver to really drive it at that limit to extract the ultimate lap time. By doing what we’re doing, we’ve made it better for the drivers. And then literally we were looking at the percentage of grip to then achieve the goal [the FIA was] looking for.’

The final iteration of tyre performed as the FIA had intended, but caused the amateur drivers to complain, both in private and in public.

‘With anything that’s so well established you put yourself in a very difficult situation because, no matter what you change, people aren’t going to like it,’ notes McGregor.

‘You’ve had open tyre competition for the last four years, where two manufacturers are pushing to the limit to beat each other.

Now though, no matter what you sacrifice, someone’s going to come back and go ‘well, I don’t like it’, so it was a no-win situation.’

Having hit the targets set by the FIA, and with the teams pushing for a better product, Goodyear had no option but to take the issue back to the FIA. ‘They asked us if we had something between this spec and where we started, and that’s when we said yes,’ recalls McGregor. ‘As a collective group, we’ll review and then see what we do moving forward, whether we stick to one or whether they want something else in the portfolio.’

Goodyear, like Michelin, has brought the latest tyre technology to the WEC, including a new wet construction and groove pattern.

‘By having hand-grooved tyres, it means you can do a lot of work quicker on developing patterns and understanding them before you then go into modern technology,’ explains McGregor. ‘So we’ve been working on the whole moulded wet tyre scenario. The tyres are much more consistent in the wet than what we had previously. And with the slick, the construction is completely new.’

Product integration While Michelin is thinking in terms of LMDh tyre sizes, Goodyear faces the same conundrum, as the chassis in the LMDh and LMP2 classes are the same. Consequently, assuming the situation remains as it is, both tyre companies will have to produce similar size tyres for their respective categories.

‘Only when we get an end goal on the final regulations, relative to when the first car 34 Le Mans 2021 • Racecar Engineering

Goodyear’s new wet construction features moulded tread technology, where previously the grooves were hand cut into the tyres

is going to hit the track, can we really start to concentrate on what we are going to do,’ says McGregor. ‘And without knowing where the calls are going to be from the performance level, it’s very hard to say what type of technology we’re going to put into work.

‘It’s completely new sizes for us that we’ve never done before, so it is a good opportunity for us to start with a blank sheet of paper.’

One of the key development improvements from Goodyear is the integration of the racing programme with the company’s production tyres. The transfer of learning from one to the other is vital for the company. Goodyear is OE on Porsche’s GT3 R road car, which uses a race tyre designed for the road and the transfer of learning from one to the other is vital.

‘We’re doing more than two Formula 1 races on one set of tyres and maintaining a level of performance, and that’s the technology people are now looking for, both in sustainability and being able to go further on a set of tyres,’ highlights McGregor.

Racing accounts for around one per cent of Goodyear’s total tyre output in a year, so bringing the racing development into the same arena as product has been a big help.

Both manufacturers are pushing for sustainability, both are trying to reach the FIA performance targets, and both have a lot of learning to do ‘One of the reasons for putting this into that in the first place is the impact of the standalone facility is much greater when it’s separate to everything else from a mainstream plant,’ says McGregor. ‘Now we can use machines and equipment that are used in other product and transfer technology across from one to the other.’

Both manufacturers are pushing for sustainability, both are trying to reach the FIA performance targets, and both have a lot of learning to do over the next few years. They may now be sole suppliers, but it does not mean the learning has stopped.

Photo: Author

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CHEVROLET CORVETTE C8.R | CHEVROLET CORVETTE C8.R

Genetically modified

After nearly 20 years of turning up at Le Mans with thundering front-engined racers GM has switched to a mid-mounted layout for its Corvette C8.R

36 Le Mans 2021 • Racecar Engineering

‘It’s a design change and there are pretty much zero carry-over parts compared to the C7.R’

By opting for a mid-engine layout GM broke with tradition with its Corvette C8.R. Since its launch in 2019, covered here, the car has continued the fabled marque’s very long run of success

By ANDREW COTTON

Racecar Engineering • Le Mans 2021 37

CHEVROLET CORVETTE C8.R | CHEVROLET CORVETTE C8.R

O

ne unbroken feature at Le Mans for 20 years was GM’s Corvette racecars, competing in the GTE Pro category. Covid brought that run to an end in 2020, but the record was the longest uninterrupted run of appearances by a manufacturer team in the history of the event. Throughout this campaign the company relied on front-engine cars, from the C5.R to the C7.R, but at the tail end of the 2019 season, it released the racing version of the first production mid-engine Corvette, the C8.R GTE/GTLM car.

Since the Chevrolet Corvettes first rolled down pit road at the circuit de la Sarthe in 2000 there has been a close relationship between the road and race departments. Lessons learnt from the C5.R were translated into the C6 that was produced for the road, and the learnings from that were put into the C6.R that raced at Le Mans for the first time in 2005, winning the class on its debut. The C6.R fed into the C7, and the C7 into the C7.R that debuted in 2014.

However, bucking the trend, the C8.R is a totally new concept; a mid-engine design, a departure from anything that the company has raced at Le Mans before. At the launch, in Road Atlanta during the Petit Le Mans IMSA finale,

both the road and race teams were tight-lipped about the new road car; the C8 Stingray. They were also a little reticent when it came to the racecar too, as it had not yet been homologated.

The car has since gone on to match the success of its predecessors. After a long testing programme, it raced for the first time in 2020 in the IMSA United Sportscar Championship and came away with the title. The team had a stunning run of success after the Covid-induced break early in the season to take both the manufacturers’ and drivers’ titles. It was a long road to that result, however, and its started more than two years prior to Daytona 2020.

Road and track

The design team started the programme with a clean sheet of paper, and unlike previous programmes that fed into each other, this one started with input from both production and race departments simultaneously.

‘It was important for us to develop the new racecar alongside the production car, so that each product could properly take advantage of the new architecture,’ says Ed Piatek, Corvette chief engineer on the road car side. ‘The benefits of this mid-engine supercar will be obvious on the street and the race track.’

Anyone who says that a Corvette should be front-engined might be right, based on recent history, but at the launch the company was keen to explain that the so-called father of the Corvette, Zora Arkus-Duntov, designed the CERV 1, a mid-engine car, as far back as 1960. Various other mid-engine Corvettes have been produced, including the Astro II, but this is the first one that has actually been put into production. The layout of the C8.R brings the Corvette into line with Ferrari and Porsche, both of which carry the engine ahead of the rear wheels. But more importantly it opens up a lot of benefits from an aero standpoint.

‘There was a rule shift back in 2016 in GTE that allowed bigger front diffusers, bigger rear diffusers, and on the C7 there was small evolution because to actually utilise them you need to make fairly large subframe changes and also suspension changes, and so, knowing the future and what was coming [with the new C8], it wasn’t going to be worth tearing the car up,’ says Corvette Racing’s vehicle integration engineer Ben Johnson. ‘Knowing that was to come, we were able to maximise the front and rear diffuser at the beginning.

‘We started our aero tuning studies in the DIL [Driver in the Loop] rig, giving the aero team

‘It was important to develop the racecar alongside the production car, so that each product could take advantage of the new architecture’

38 Le Mans 2021 • Racecar Engineering

as much freedom as we could. We said: “here’s the free volumes from the FIA, do whatever you want in here and we will build the structure around it”. There are always compromises and limitations, but that’s why it is such a departure from C7 in terms of those structures just to maximise the aero. There still may be Balance of Performance, so the lap times will be the same [as C7.R], but it helps you in terms of stint performance and tyre performance and different ambient and track conditions.’

Paradigm shift

Moving the engine to the mid-section of the car freed up the design team to play with the front diffuser, while a small Xtrac gearbox at the rear

– bespoke for the car – has allowed for a more efficient rear diffuser. The entire underfloor has been sculpted to clean up airflow to the rear of the car, while the over-body sees a few slight departures from the production C8.

‘Everyone pushes the wing as far back and high up as they can and then you section the rear fascia at the maximum line to help rear downforce and extraction,’ says Johnson of the design at the rear. ‘There is a lot of work on the diffuser, but one of the advantages of a clean sheet design front and rear is the communication between the two, and they have a better relationship.

‘You are trying to manage the airflow to the front and maximise the downforce there,

There have been mid-engine Corvette concepts in the past – pictured is the 1968 Astro II – but the C8 is the first on the road

and also feed the diffuser to achieve the balance,’ Johnson adds. ‘You could produce more downforce on the front, but you could never balance the car and it is those studies, controlling pitch sensitivities and all those aspects, that give you the performance. You can find those balances in the DIL rig and give the group those targets, rather than them trying to find it all through downforce and then having a penalty for balance or stability [later].

The iterative loop of that, trying to do it up front rather than scrambling to do it when you get to full size, is that [at full size] the parts changes are expensive and complex.’

Rear view

Having the rear wing pretty much in the driver’s eye-line at the rear means rear visibility relies on the rear facing camera that was introduced by the team with Bosch. The racecar also features an engine intake at the bottom of the rear window. This was an area that had minimal impact on airflow to the wing, but it was not an idea adopted for the production car as it would have disturbed rear visibility for the driver.

‘On the production Stingray we draw the induction air through the openings on the side of the car, but when we did the modelling for the aerodynamics on this car, especially because all racecars come with a rear wing, if you pull air off the rear window you clean up the boundary layer and make the wing more efficient, while getting some good ram high

The design of the rear diffuser has been exploited to the maximum, while a small and bespoke Xtrac gearbox plus a sculptured underfloor helps to clear up the airflow to it. The huge wing means the view out the back is via camera only

‘The aero rules are pretty narrow to control costs, but we took the opportunity and made big advancements’ Racecar Engineering • Le Mans 2021 39

CHEVROLET CORVETTE C8.R | CHEVROLET CORVETTE C8.R pressure flow for the intake,’ says Piatek. ‘It was a solution that works well on the racecar, but on the road car it would hurt visibility.’

By placing the intake where it is in the rear of the racecar, it freed up the air intakes on either side of the car for other cooling purposes.

This was critical, because while the old car had the engine at the front and gearbox at the rear, meaning a long prop-shaft, now all the components are housed in the same area.

But this means there are other things to worry about. ‘Thermal management is a big challenge,’ Johnson admits. ‘Before, we had the temperature of the gearbox and thermal load of the gearbox at the back of the racecar and the engine at the front of it, and you could manage them separately. Now they are in the same area, and then things that want to be cool, like the compressors and alternators, are in the same area, so where before you could rely on passive cooling, there’s now heat shielding and active cooling going on.’

design that was not previously available to the team before, with the front-engine layout.

‘The front wheel arch you can’t vent by rule, but [the exit] is the radiator exit and that helps you with wing performance and giving the best air onto the wing,’ says Johnson. ‘These exits are used differently to the production car. Normally with a front-engine car you are doing it all at the front, so you somehow compromise the radiator. You either have more things in the water loop that you have to cool, or you are

stacking radiators, which all add to cooling performance, so the exits on the side of the racecar help with the gearbox and air conditioning and things like that.’

The upper surfaces of the racecar are very close to that of the production car that was presented earlier in 2019, per regulation, but there are clearly a lot of design tweaks that were designed to improve the car’s performance on track. Incidentally, developing both road and racecar at the same time was the model used by

Cool pack

Where the production car has its luggage space at the front, the race team has used the area to house a single front radiator, following Porsche’s design – before it changed this the German manufacturer had a radiator on either side at the front, which frequently led to leaks following ontrack incidents. Air extraction on the C8.R is via the ducts behind the front wheels, an efficient

Incoming brake supplier Alcon has produced new and larger front and rear discs and bigger pads for the Corvette C8.R

The chassis for the C8.R is based upon the convertible Stingray. It’s been constructed using new processes designed to increase its stiffness while reducing its weight

‘Where with the front-engine Corvette you could rely on passive cooling, there is now heat shielding and active cooling going on’ 40 Le Mans 2021 • Racecar Engineering

‘I would think that we are not at a performance level yet that we could get through Le Mans or Daytona without changing brakes’ Ford with its GT, with Canadian firm Multimatic developing both in conjunction with each other. The Ford GT went on to have a successful endurance career, which was brought to a close at the Petit Le Mans. Multimatic has now turned its attention to the Aston Martin Valkyrie hypercar, and is producing the track version alongside the production car once again.

Cabin pressures

Photographing the cockpit of the C8.R was not permitted at the launch, as this was a test car, one that was not yet perfected for racing.

But the team did admit that, after careful consideration, it had decided to maintain a dashboard mounted display rather than put everything on to the steering wheel, as other manufacturers have opted to do. It has also talked to drivers about switchgear layout and cleaned up that area so that they are not searching around for the right switch in the middle of the night on the Mulsanne Straight.

Working with Bosch, engineers believe they have made significant improvements to the layout. They have also carried over all of the safety aspects that were designed and While the side intakes give a clue to the engine position these aggressive looking ducts are for cooling purposes only and the main air intake for the power unit is on the rear of the C8.R

implemented into the C7.R, including a fixed seat and side impact protection.

Under the skin there are some significant changes compared to the C7.R. Corvette switched to Alcon for its stopping power, and the firm produced new size front and rear brake discs and pads specifically for the Corvette, due to its unusual needs.

‘We did a big benchmarking study and all the suppliers are converging on to some really good parts, so there are small deltas to work on,’ says Johnson. ‘But Alcon has been really good to work with on a technical partnership and every car packaging is slightly different, and they were happy to work with something that was for our car rather than an off-the-shelf thing. This car has more rear weight bias [than the C7.R], and you run more rear brake than on the C7 so they have grown in size, and we have a much bigger rotor [disc] on the front. Ultimately with braking you are still limited by aero force and tyre grip, but having the larger components can help in endurance racing and can give you bigger windows for brake changes and things like that.

‘I would expect that we are not in a performance level yet that we can get through

Le Mans or Daytona without changing brakes,’ Johnson adds. ‘You could probably choose a pad that would get you there, and we don’t have that information yet, but you would likely want a pad that you change once but then have more ultimate performance. The sporting rules [had] dictated that there was no penalty for changing brakes at Le Mans, but now there is one. Making up the 20 seconds of a brake change [isn’t so difficult, because] making up 15 seconds on the track is possible if the drivers are more comfortable on the brakes.’

Chassis secrets

The collaboration between road and racecar on the chassis side is evident with the suspension pick up points, which are the same for both products. Yet here, for the first time, the team started to evade Racecar’s questions a little.

‘We had a completely clean sheet as to how the chassis is constructed and the suspension mounted, so we could optimise all of that,’ says Johnson. ‘People will want to get their eyes on it. It is not something that you are going to say “I’ve never seen that before,” but we have put a lot of work into everything and we have come

CHEVROLET CORVETTE C8.R | CHEVROLET CORVETTE C8.R

‘Things were coming loose in testing that we never thought about on the C7.R – over a 24-hour race that’s going to be interesting’ up with something that we like so far.’ No doubt the homologation papers will reveal everything, but the C8.R racecar has yet to finalise that process – hence the reticence.

The chassis construction itself has actually made use of the convertible layout, with new processes designed to increase stiffness and reduce the weight of the base chassis. By increasing the strength and stiffness the team has reduced the demand on the roll cage fitted to the car. It also means that any weight added to the car can be introduced lower down, helping with overall performance.

Weighting game

The team was unwilling to give out any figures on weight distribution, other than to say that it drove everything from aero loads to tyre specification. ‘The initial deal that you have to do is based on this weight distribution, we want this aero, and come up with a trade study knowing the limitations of the tyre development,’ says Johnson. ‘You try to come to a point that you make the decisions early on before you ever get to the track, that what you are utilising doesn’t become a problem where you are rear grip limited because you have too much at the front of the car, or you are asking too much of the rear tyre because of the weight distribution. With the base weight distribution, the ability to shift it within the regulations, we have a pretty wide envelope. We can move the engine as close to the centre of gravity as you can, but there are limitations on the firewalls,

chassis structures and fuel cells and so on. The rules save you from yourself.’

While moving the engine to the centre of the car may seem extreme, so might be the new engine itself. That said, very few details were available, not only due to homologation but also because it hasn’t yet been announced what engine is coming for the production car. It is believed that there will be a 500bhp normally aspirated engine, then a 700bhp turbo, followed by a 900bhp hybrid. For now, this is a 5.5-litre flat plane crank normally aspirated design.

‘If you have a four-valve engine, it breathes better and you have a lot better efficiency, and a flat plane crank doesn’t have counter weighting on the crankshaft, that gives you better response, and those are the primary reasons why you would do a flat plane crank,’ says Piatek. ‘You don’t put counter weighting on the crankshaft, but there is very significant second order lateral vibration that you have to manage, but you do get the responsiveness.’

These vibrations have been something of a headache for the Corvette race team. The impact of the vibrations was already known, and so the design accommodated it as much as it could, but there were still areas that shook themselves loose in testing.

‘It is a challenge,’ admits Johnson. ‘It is something we knew was coming in from the production team, the modes of the vibration, and we built in as much as we could to put our operating range outside of those excitation modes. We have seen things in testing that we

have had to address due to the vibration, but nothing fundamental, nothing that has stopped a test or required huge changes to the car, but things were coming loose that we never thought about on the C7. Over a 24-hour race that’s going to be interesting.’

The mid-engine layout has meant a shorter propshaft, which itself acts as a damper and was able to mask some of the vibration from the gearbox. ‘You stiffen it and it isolates a lot of the shifting vibration and the modes between the engine and the gearbox, but ultimately getting it out of the system is a known challenge,’ says Johnson. ‘It’s a design change and there are pretty much zero carry-over parts compared to the C7. The whole time you are looking at every system on the C7 and saying that you cannot apply that directly. So, we had to look at how you take the principles on C7 and then do them on a new platform.’

Record runner

The car has proven itself in competition, winning the Daytona 24 hours in 2021 on its way to the championship, but due to Covid the car’s Le Mans debut was delayed to 2021.

Due to Covid the FIA WEC also missed the double header event at Sebring in March at which it could evaluate the Corvette, and so instead the team competed at Spa in May so that the balance of performance could work.

With IMSA cancelling the GT LM category for 2022, the C8.R will likely be seen more often in Europe in 2022.

The GTLM version of the C8.R won the championship in 2020 and the Daytona 24 hours in 2021

42 Le Mans 2021 • Racecar Engineering

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MAZDA | ROTARY ENGINE

Rotary club Mazda developed its rotary engine for Le Mans and in 1991 took full advantage of the regulations to produce a winner

By Wouter Melissen

T

here is an old saying in racing; Le Mans chooses her winner. Due to the nature of the event, each winner earns a place in history.

Few victories in the French classic, however, were quite as historic as Mazda’s in 1991.

The headlines after the race 30 years ago read that Japan had finally scored its first win at the 24 Hours of Le Mans after many attempts by Nissan, Toyota and Mazda.

That the smallest of the three Japanese companies broke the country’s duck may have come as bit of a surprise but Mazda did stage the most focused effort.

It was the result of a carefully planned and perfectly executed plan that was more than deserving of the victory.

While chasing the win was the ultimate objective for the others, Mazda also very much considered it a means to showcase the capabilities of the ‘Wankel’ or rotary engine. Accordingly, the Le Mans in 1991 was as much a proof of country as it was a proof of concept.

Head spin The shriek of the Mazda rotary was first heard at Le Mans in 1970 courtesy of a twinrotor engined Chevron B16. In 1968 and 1969, similarly equipped production-based Mazdas had already been raced in Europe.

Impressive results were achieved at the gruelling Marathon de la Route, an 84-hour race at the Nurburgring and in the Spa 24 Hours. These international competition efforts came just a few years after Mazda had managed to create a production-ready version of the rotary engine first patented

by German engineer Felix Wankel in 1929.

Instead of conventional pistons, this design features a triangular rotor that spins in an oval chamber on an eccentric shaft.

The intake, combustion and exhaust ‘stroke’ occur in a single revolution of the rotor.

As a result, the rotary had the potential to become a smaller, lighter, less complicated alternative for conventional engines.

This potential was first recognised by motorcycle and automobile manufacturer NSU, who started developing the rotary 44 Le Mans 2021 • Racecar Engineering

engine in earnest in 1951. To speed up the development, NSU licensed the technology to a large number of other companies that included the likes of General Motors, Mercedes-Benz, Porsche, Rolls-Royce and also to Japanese companies Nissan, Toyota and Mazda. For larger applications such as airplane engines, NSU also partnered with Curtis-Wright. The high power-toweight ratio made the rotary engine particularly interesting for use in airplanes.

The major issue all license holders faced was the durability of the apex seals fitted on the three tips of the rotor. These seals were crucial for creating the compression required for the combustion. The tips of the rotor reached very high velocity, so the seals needed to be both very strong but also delicate enough not to damage the combustion chamber. NSU and Citroën moved ahead and introduced rotary engined cars without fully sorting this issue, which led to many problems and bad publicity. Eventually both companies abandoned the unconventional engines.

Most other manufacturers did not get beyond the experimental phase.

There were two exceptions. Both CurtisWright and Mazda claimed to have found a solution for the situation. Seemingly working independently, the American and Japanese companies both settled on using carbon for the apex seals. A small drop of oil was added to the fuel mixture to aid cooling. By the mid-1960s, the Mazda engine was ready to enter production, debuting in the fabulous Cosmo Sport coupe introduced in 1967.

Cosmo conundrum That both Mazda and Curtis-Wright came to the same solution at around the same time was long believed to be a coincidence. That was until Mazda North America decided to add a Cosmo Sport to their collection to celebrate the model’s 40th anniversary.

The model had never been sold new to the United States, so there were some raised eyebrows when they came across an example that had actually been first registered in the country. The first owner

The rotary had the potential to become a smaller, lighter, less complicated alternative to conventional engines

Photos: Wouter Melissen

Carbon tips on each of the corners of the rotor were added, as was oil in the fuel mixture to reduce temperatures

was none other than the Curtis-Wright company, which could still be explained by the fact that the American company actively sought to acquire rotary engined machines for research purposes.

The plot really thickened when a large stash of Cosmo parts were offered on an American online marketplace. Mazda NA immediately reached out to the vendor both to buy the parts but also to find out the story of how he got hold of them in the first place. As it turned out, the gentleman offering the parts was a former CurtisWright employee. He went on to reveal that he had seen Kenichi Yamamoto, the father of the Mazda rotary engine, several times at Curtis-Wright. So it may very well be that the fiercely independent Japanese company had been a little more pragmatic when developing the rotary engine and Racecar Engineering • Le Mans 2021

45

called in outside help. If this was the case, it was definitely the right move as Mazda would go on to produce rotary engined cars long after all other manufacturers had abandoned the technology.

From the start, Mazda used motor racing to make the case for the rotary engine. The production-based RX-7 was a particularly successful in GT and touring car events. Tom Walkinshaw Racing prepared examples, scored an outright victory in the 1981 Spa 24 Hours and with Win Piercy won the 1980 and 1981 British Touring Car Championship.

RX-7s had also raced at Le Mans and in 1983, the Japanese manufacturer’s motorsport subsidiary Mazdaspeed decided to step up to the prototype ranks once again. Using a derivative of the RX-7’s R13B engine, the purpose-built Mazda 717C was created for the Group C Junior class. The compact and lightweight rotary engine was best suited to the new category as it could not match the power of the turbocharged Porsche and Lancia engines used in the top class.

XPB

MAZDA | ROTARY ENGINE

Mazda’s 717C raced at Le Mans in 1983 as a prototype for the first time, featuring a rotary engine

Moonshot Like all production Mazda rotary engines to that point, the R13B consisted of two rotors that were stacked. Each combustion chamber displaced 654cc for a total swept volume of 1308cc. To level the playing field with the piston engine competitors, an equivalency factor of two was applied to rotary engines. The logic behind this was that it had a combustion cycle on every rotation of the crankshaft instead on every other rotation as with a conventional engine. The tiny unit produced around 310hp and was mounted in an aluminium monocoque that was designed and built for Mazda by specialist company Mooncraft.

Run with the local support of Alan Docking, Mazdaspeed entered two 717Cs at Le Mans in 1983. They finished 12th and 18th overall. With no other C Junior car crossing the line, this was more than enough to win the class. In 1984 and 1985, Mazda fielded the 727C and 737C evolutions in what was now the C2 category, but they did not have the same level of success. In 1984, the works team was beaten by the 13B-engined Lola T616s of the American BF Goodrich team. Running on productionspecification rubber, the Mazda-engined T616s were, however, very successful in the North American IMSA GTP Championship.

Ahead of the 1986 season, Mazda decided to raise the bar and develop an engine and a car capable of winning sports car races outright. The impetus behind the move was the addition of a GTP class at Le Mans, which had a lower minimum weight limit than the top level Group C1 class but with a similar fuel allocation. Dubbed the Mazda 757, the new GTP racer would 46 Le Mans 2021 • Racecar Engineering

The engine had very little by way of torsional rigidity and so had to be housed in a cradle. In the final version the cradle was further supported by a carbon plate which proved to be strong enough to win

be the first sports prototype developed and built in-house by Mazdaspeed As per Docking’s suggestion, Nigel Stroud was hired as the chassis designer.

The experienced British engineer had just created a bespoke chassis for the Porsche 956 and 962Cs run by the Richard Lloyd team. Stroud created a straightforward aluminium monocoque. Like his version of the 956/962 tubs, the aluminium sheets used for the Mazda monocoque featured a honeycomb core for additional strength.

Effectively a stack of discs bolted together, a rotary engine certainly did not have the torsional rigidity to be mounted as a fully stressed member. Accordingly, a

Like all production Mazda rotary engine to that point, the R13B consisted of two rotors that were stacked

Japanese engineers discovered that the additional power did not weigh up against the detrimental effect on engine reliability and fuel efficiency, so added a third rotor separate tubular subframe was bolted to the rear bulkhead to support the engine, gearbox and rear suspension.

To compete at the sharp end of the field, more power was also required. Mazdaspeed had experimented with a turbocharged version of the twin rotor engine in a March GTP chassis. The Japanese engineers quickly discovered that the additional power did not weigh up against the detrimental effect on engine reliability and fuel efficiency. Instead, it was decided to add a third rotor to the existing engine. The resulting type 13G unit displaced 1962cc and produced 450hp.

The Mazda 757 boasted a Porscheinspired rear-end that included a Porsche five speed gearbox. Like the 956 and 962, the rear suspension featured in-board

springs and dampers that were actuated by rockers mounted on the top wishbones.

At the front, the in-board springs and dampers were pull-rod actuated.

Already stretched, Mazda’s limited resources meant there were no funds to test the original 757 shape in the wind tunnel.

The design was somewhat reminiscent of the Porsches on which Stroud had previously worked and they were good enough to race.

Two 757s were entered for the 1986 Le Mans and ran well until driveshaft failures forced both cars to retire within a few laps of each other. Undeterred, Mazdaspeed continued the development work and was soon ready to reap the rewards.

Further refined 757s returned to Le Mans the following year, for the 1987 event. Not only were the cars improved, the Mazdaspeed crew were also learning with every outing. While one example suffered an engine failure the surviving car finished seventh overall. This was the best result yet for a Japanese car and also enough to win the GTP class.

The next step in the evolution was the Mazda 767 that debuted in 1988. It featured a four-rotor engine. Rated at 600hp, it was much more powerful than the earlier engines, the type 13J-M also demonstrated that the stacking of rotors was not limitless. Torsional rigidity proved a problem early in the car’s development.

This was cured by bolting a carbon fibre composite plate to the top of the engine.

The 767 had been developed in just three months, so Mazda decided to hedge its bets and not only field two of the new cars, but also one of the earlier 757s. It was a wise choice as the faster 767s both suffered from failed exhaust manifolds and stripped water-pump gears, again within just a handful of laps from each other. The two machines were repaired but finished well down the order. There were no such issues for the 757, which scored the second GTP win in a row for Mazda.

Now fully developed, the new-for-1989 767Bs once again showed well, finishing seventh, ninth and twelfth overall and first, second and third in the GTP class.

Time warp Winning the GTP class three years running was a commendable achievement and a better result than the other, much better funded Japanese manufacturers had managed. Time, however, was running out for Mazda as a major regulation change loomed. A second generation Group C class was planned, designed around a 3.5-litre naturally aspirated engine, bringing sportscar racing in-line with the contemporary Formula 1 engine regulations.

In these rules there was no allowance for rotary engines. When the plans were first announced, the idea was for the new cars to take over from the 1991 edition.

For Mazda, this was a small disaster as it had just developed a two-year plan around Mated to a Porsche gearbox the 787B targeted a specific distance for the 1991 race, and needed to run reliably with a maximum of 75 minutes in the pits over 24 hours

Racecar Engineering • Le Mans 2021 47

MAZDA | ROTARY ENGINE the all-new 787 prototype, which in its for1991 787B guise would boast 800hp and be capable of 350km/h. More determined than ever, Mazda set about creating the new car and opted to squeeze as much of the planned technology into it for its first and perhaps last outing at Le Mans.

Le Mans legend Jacky Ickx was hired as a consultant and the team also looked at young talents to strengthen the driver ranks.

Mazda’s head of engine development Yasuo Tatsutomi faced the arduous task of increasing the rotary engine’s output considerably but also keeping the fuel consumption down sufficiently for the car to actually reach the finish with the allotted 2550 litres of fuel. Adding another rotor was not an option due to the concerns over the torsional rigidity.

Tatsutomi quickly realised that the existing design would just not suffice and instead developed a brand-new four rotor engine.

One step beyond Known as the R26B, it yielded the major step forward that was required to vie for the outright victory. No longer based on the RX-7 production car engine, the new unit was considerably lighter. It also featured a variable intake system that allowed the trumpet length to be adjusted in several set steps. The primary objective of this system was to help the engine to produce maximum torque over a wider rev range.

The rotors were fitted with carbonfibre composite apex seals for improved durability. In addition to the apex seals, another weak spot of the rotary engine was the incomplete combustion, which affected the fuel efficiency and later in its ‘civilian’ life caused insurmountable emission issues. On the R26B that issue was somewhat addressed by adding a third spark plug to each combustion chamber.

Still mated to the Porsche 956-derived five-speed gearbox, the R26B was good for an impressive 700hp in race trim.

For the all-new engine, Stroud laid down a fresh monocoque chassis design.

This was built in carbon-fibre composite by specialists Advanced Composite Technology in Great Britain. Whereas the 757 and 767 had featured lateral radiators, these were moved to the nose of the 787 with an eye to improve efficiency.

Mazdaspeed also experimented with spats on the rear wheels, which were also fitted to the successful Jaguar Group C cars fielded by old partners TWR. In addition to producing a brand new car, Mazda also introduced new technology; it was the first Japanese manufacturer with access to an IBM machine. The 787s were fitted with a telemetry system that allowed the engineers to monitor 48 Le Mans 2021 • Racecar Engineering

A complex ECU was able to control the continuously variable intake trumpets. The 1991 engine was a departure from the road-based units that had gone before, being lighter in weight and more powerful

the car from the pits in real-time. A race simulation system was also pioneered, which enabled the Japanese engineers to simulate the Le Mans track, where regular testing was of course not possible.

Two 787s were entered for the race with one car manned by experienced hands Stefan Johansson, Pierre Dieudonne and David Kennedy and the other by youngsters Bertrand Gachot, Johnny Herbert and Volker Weidler. With an all-Japanese crew on-board, a 767B was also entered as a back-up. The 787 design had clearly been rushed as both were forced to retire with mechanical issues. Running the third car proved wise once again as it scored yet another GTP victory for Mazda.

Weight watcher A delay in the introduction of the second generation Group C cars saw the regulation changes postponed by one year. To ensure that the manufacturers would continue to develop the 3.5-litre machinery, weight and fuel allotment penalties were imposed to the existing cars. These were all slotted into a single ‘Category 2’ class. Furthermore, the new ‘Category 1’ cars would line up on the grid first regardless of the results in qualifying.

Mazda was determined to make the most of this unexpected reprieve. Long before the 1991 race, it had already scored a major victory. The cars that had raced in the Group C class were handed a 200kg weight penalty, bringing the limit up to 1000kg.

For the old GTP class machinery, such as the Mazda 787, an 850kg limit was set. Thanks to extensive diplomatic work, Mazda convince the governing body to reduce that to 830kg.

A third spark plug was added to complete the combustion process, again with a view to improving fuel consumption

Instead of determining how to make the car faster, Inoue first set about determining how fast the car needed to be to win the race

Mazda’s 787B had a reprieve to run one more year, as GTP competitors had a weight advantage compared to Category 1 cars, and then negotiated an even lower weight limit, critical in a fuel-limited formula

wheels were fitted and the uprights were changed from magnesium to steel.

The already mighty R26B engine also received one significant upgrade; it now featured continuously variable intake trumpets, controlled by the ever more complex ECU. Power remained largely the same but the torque increased by a hefty 40Nm, a crucial difference on a track that had more corners than ever before.

The rear subframe was also revised, and the rigidity was increased considerably by only adding two engine mounts.

Already on borrowed time, the Mazdaspeed operation set out to be better prepared than ever before for the 24 Hours of Le Mans in 1991. Team consultant Jacky Ickx suggested partnering with Hugues de Chaunac’s ORECA team to test and race the new cars. The six-time Le Mans winner had just raced with de Chaunac in the Dakar rally and was hugely impressed with his operation, which was conveniently located near the high-speed Paul Ricard circuit. Ickx considered it crucial to perform at least one 24-hour test before the race. In the end two 5000km tests were conducted, one with a modified 787 early in 1991 and a second with the 787B in its ultimate specification.

Max attack

The carbon ceramic brakes forced a redesign, with the uprights changed from magnesium to steel, while larger wheels were fitted to cope with the increased heat generated. Engine mounts were also added

Using the race simulation software introduced in 1990, a young Japanese engineer by the name of Hiroshi Inoue decided to look at the race from a completely different angle. Instead of determining how to make the car faster, Inoue first set about determining how fast the car needed to be to win the race. His calculations set the distance required at 367 laps, taking into account spending just 75 minutes in the pit-lane. This meant that the target lap time during the race would have to be improved by a full seven seconds without affecting the fuel consumption.

The addition of chicanes at Le Mans also meant that the emphasis switched from straightline performance to cornering capabilities. Additional downforce was generated by lengthening the nose by 25mm and the rear suspension was revised to allow for a 50mm wider thread.

Breaking new ground, the 787B was the first Le Mans car to be fitted with carbonceramic brakes. The discs themselves were supplied by Carbon Industrie, while the calipers were sourced from Brembo. To cope with the extreme heat generated by the composite brakes, larger

Better prepared than ever, Mazdaspeed fielded three cars once again; two 787Bs and a 787 as back-up. Among the main rivals were the Sauber-Mercedes and TWR-Jaguar teams, which had won the race in 1989 and 1990 respectively. Both had developed new Category 1 cars, which were blisteringly fast over a single lap but it was highly uncertain if they would last the distance. Instead both teams fielded grandfather Category 2 cars despite the 200kg weight penalty. The only works team to line-up with a Category 1 car was Peugeot, who had no choice and entered a pair of V10-engined 905s. In qualifying a Sauber-Mercedes had set the fastest time of all but had to start in 11th as it had to line-up behind all of the Category 1 cars. The lead Mazda piloted by the three youngsters, Weidler, Herbert and Gachot, had been 12th fastest and lined up in 19th.

The two Peugeots were on the front row for the start but as expected, neither made it past the six-hour mark. A SauberMercedes emerged in the lead but the team’s other cars all struggled with issues, most related to additional weight the C11s had to carry around and were not designed for. The Jaguar XJR-12s had no reliability woes but in their case the additional weight forced the cars to slow down considerably during the morning amidst fears of running out of fuel. What caught both seasoned teams completely off guard was the pace at which the Mazda could lap during the Racecar Engineering • Le Mans 2021

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MAZDA | ROTARY ENGINE race. Meeting the parameters set by Inoue, the bright orange and green 787B turned out to be Mercedes’ main challenger.

Not only did the shrieking Mazda not allow the big Sauber-Mercedes to settle down in a rhythm that might see it to the finish without any major issues, but Weidler, Herbert and Gachot were actually able to up their pace and hound the silver arrow down. The strategy worked as Alain Ferté was forced to pit the lead C11 at around noon on Sunday as a result of a water pump failure that led to a large cloud of steam.

With just a handful of hours to go, Mazda was in the lead and there was no stopping the rotary engined machine. Having eventually completed 362 laps and two more than the nearest rival, Weidler, Herbert and Gachot scored an historic victory.

For Mazda it was the culmination of a determined programme that had started almost 25 years earlier at the Nurburgring, proving that the rotary engine could succeed at motorsport’s highest level.

During the race, the Mazda engineers had needed to replace only a blown light bulb and as a precaution the right rear wheel bearing was changed. Following this near faultless run, the Le Mans winning car was disassembled in Japan in front of the gathered media. Discovered was regular wear and tear expected from racing at Le Mans for 24 hours but it was determined that the engine could easily complete another edition of the race. The winning machine was put back together and was used for demonstration purposes only.

To celebrate the 20th anniversary of the historic victory, it was decided to restore the car in 2011. At that time, the car had not been run for five years. The engine nevertheless required minimum attention with some parts replaced by spare parts that Mazda had kept in stock all those years. Since then, it has been regularly demonstrated at events around the world.

It was not until the 2020 Sebring 12 Hours that a Mazda took an outright victory in one of the classic endurance races again

Return of the mac Mazda did return to Le Mans in 1992 but with a regular piston engined Category 1 car. This was based on the Jaguar XJR-14 and used a Judd-supplied V10 engine. It was not a success and after that Mazda’s sportscar racing operation focused mainly on the United States. When the rotary engine was finally phased out of production nearly a decade ago due to ever stricter emission regulations, the company’s effort changed to piston engines. It was not until the 2020 Sebring 12 Hours that a Mazda took an outright victory in one of the classic endurance races again.

While Mazda currently no longer offers the rotary engine, the technology has not been forgotten at the headquarters in Yokohama. Even NSU, long absorbed by the Volkswagen Group, brought it back from the dead, pressing a rotary engine into service as a generator for an electric powered Audi A1. The thought of doing something similar is what has kept Mazda from abandoning the rotary engine altogether.

Mazda remained the only Japanese company to win at Le Mans until 2018

when Toyota finally managed to repeat that feat. Perhaps it was not a coincidence that it did so with engineering and logistical support from ORECA. At first glance, Mazda’s historic win at Le Mans may have looked like a fluke but it was the result of many years of sheer determination, careful planning, superb engineering and a stellar driving effort. Mazda used its relatively small budget to its advantage to focus on one solution whereas Nissan and Toyota explored so many avenues that it was nearly impossible to win the race.

A more detailed and beautifully illustrated account of this fabulous journey can be found in the ‘Never Stop Challenging’ book that former driver and team manager Pierre Dieudonne wrote on the occasion of the 20th anniversary of the victory, in 2011.

Rebuilt using parts kept from the 1990s the Le Mans winner still completes demonstration runs, here at Goodwood Festival of Speed in 2015

50 Le Mans 2021 • Racecar Engineering

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