14 minute read
IMSA race strategy
Strategic command
Race engineer and strategist, Jeff Braun, explains how teams in IMSA have to play the strategy game to be in with a chance of victory
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By ANDREA QUINTARELLI
Top motorsport classes are often associated with an environment where the quest for pure performance is the heart of every decision, both on track and out of the circuit. Indeed, the main goal of a racecar is to perform better than its competition.
Winning races is not ‘just’ this though. In the past, with less advanced tools at engineers’ disposal, reliability was a crucial factor, and the really good drivers knew they had to be kind to their hardware during a race to avoid a retirement.
Nowadays, retirements because of reliability issues are much less frequent than they once were, but there are still important aspects that transcend pure performance and can make a big difference on race and championship results. Among the most important ones is how a team handles race preparation and strategy.
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Richard Dole
If a team’s pre-race preparation is good then a car should behave over the course of a race event, so that’s when strategy comes into play, particularly in endurance racing. It can differ greatly depending on the series so the very first step is to understand the regulations for the class in which you are competing
Being prepared for a race is important in every class, and every team that is serious about winning invests time and resources into pre-event work. This can be trying to anticipate how a weekend could evolve and analysing possible scenarios, in order to have all the required information once at the track. The aim is to reduce the risk of having to work in emergency mode, while facing something unexpected, and needing to diverge resources to solve problems that could have been analysed at the factory. Of course, something unexpected can always happen, but this can even become an opportunity, if teams are flexible enough to react quickly.
Race strategy is also crucial, especially in longer competitions where teams need to perform pit stops. Besides Formula 1, where tyre management is probably the most important factor, endurance racing is the environment where strategic decisions can influence the final results the most.
In most endurance racing championships, pit stops are performed under rules that limit the number of team members that can work simultaneously on the car, but different approaches are still required, depending on the regulations. The best example is comparing the World Endurance Championship and the European Le Mans
Series with the IMSA Weather Tech Sportscar Championship. These series employ some common classes, albeit with slightly different technical regulations, but the sporting side of the racing is accounted for in completely different ways.
Racecar Engineering had a chance to talk to Jeff Braun, a highly experienced race engineer who has successfully run a diverse range of cars, from GT to IndyCar, and won every major race in North America during his career.
In recent years, Braun was mostly active in the IMSA Weather Tech Championship. In 2018 and 2019 he led CORE Autosport’s campaign in the top class, first with an LMP2 car and then with a Nissan DPi. In 2021, he again supported CORE Autosport on the strategy side in its assault on the LMP3 class.
‘The first thing you have to do is understand the rules, because they can be so diverse,’ notes Braun. ‘Take, for example, WEC and IMSA: the regulations are way different and, as a consequence, your strategy needs to work in a dissimilar way.’
One main difference between endurance racing on the two sides of the Atlantic is the way yellow flags and safety car situations are handled. While in WEC and ELMS, virtual safety cars have been implemented in the last few years, this is not the case in IMSA, where real safety cars are still employed to handle dangerous situations on track. With a virtual safety car, the gaps between cars remain mostly unchanged, while cars leading by a big margin can abruptly find competitors hot on their heels under a real safety car event.
‘We saw it often with teams coming into IMSA from the ELMS or WEC,’ continues Braun. ‘They often kept their non-professional driver for the last stints, which makes sense with virtual safety cars because if you build up a good lead during the race, you put your slower driver in a position to win, even in the event of a neutralisation. Such a situation can even help you, because the other cars have less time to catch you.
‘But this is not the case in IMSA. If a safety car comes on track during the last phases of the race, you are in a very bad position if your amateur driver is at the wheel. Your lead is gone, and you have a slower driver needing to handle a very stressful situation against a pro driver after a restart. That’s why in IMSA we always plan to have our fastest driver in for the closing stints.
‘This is just an example to demonstrate the importance of knowing the regulations.’
Driver rotation
Another critical aspect in any endurance championship are the rules related to driving time. This is tightly regulated and IMSA makes no difference with this respect, at least in longer races like the 24 hours of Daytona, the 12 hours of Sebring and Petit Le Mans.
‘In IMSA, we have what we call the ‘four-in-six rule’, which means that no driver can drive more than four hours in any six hours period… to prevent fatigue,’ explains Braun. ‘A violation of this rule leads to a huge penalty – cars have lost podium positions in the past because of not respecting it. It seems something easy to manage, but it is not.
‘Everyone wants to run their fastest driver at the end of the race but, if the same driver was in the car before, you have to be careful that the previous six-hour block of time and the current one do not overlap in a way that leads the sum of the driving times to be bigger than four hours. ‘Sometimes, to avoid a violation, you would need to have your fast driver out of the car for a few minutes before getting back in to finish the race.’
‘And, as the race engineer or strategist, you’re often having to work this out when you’re already very tired yourself, for example at the end of a 24-hour race.
‘Over the years I developed tools to help me manage driver rotations and the time they spend in the car, but I am still more worried about breaking the four-in-six rule than anything else during a race.’
In shorter races, this is not a factor, as the rules simply stipulate every driver must be in the car for at least 45 minutes.
Safety cars in IMSA bunch the field, and you need your fastest driver in to the end. A virtual safety car means you are more likely to keep your hard-earned lead and driver rotation is less critical
Knowing when to pit cars, or not, is crucial, especially in IMSA, as laps can be regained during a neutralisation event A typical data centre at a major endurance event
Another important difference between the Weather Tech Championship and the WEC or ELMS is that in IMSA it is possible to regain a lap during a neutralisation.
The pass around
‘Especially in a class with both professional and non-professional drivers in the car, having chances to get a lap back is important, and your strategy to achieve this is crucial. The longer the race, the more opportunities you may have.
‘Assuming your car is a lap down, you have to put yourself in a position to get that lap back, perhaps by offsetting your fuel strategy. If a yellow flag comes out and you manage to pit before the safety cars goes on track, you do not need to tank during the neutralisation, while your competitors may need, or want to. This way, your crew would unlap and find themselves in front of the leader, between them and the safety car. Before the race goes to green again, IMSA allows all the cars ahead of their class leaders to overtake the safety car and get behind the last car. So now your car is not a lap down any more and is right behind the cars in front. You will still need to tank before them, because you got off sequence, but at least you are in the same lap now.’
In the event of another safety car event close after, a team could even eliminate the disadvantage of being off sequence with their fuel strategy as most teams would choose to pit anyway in such a situation.
Similarly, in a scenario where a safety car needs to suddenly be sent on track, if a crew find themselves between the race leader and the safety car, they can still profit from what Braun describes and queue up behind the group, even before the pit lane is opened, gaining significant time.
‘The reason they do that is that in multiclass racing it would be unfair to block a car between the overall leader and the safety car. If you had just one class racing, the safety car would simply come out in front of the race leader. The goal is to recreate a situation where each class would have the safety car coming out exactly in front of their race leader. They call this the ‘pass around.’ After this, they do the pit stop sequencing and, before the race gets green again, there is a final ‘wave by’, where everybody ahead of their race leader can come around again. This is a kind of a free lap, and the reason they do that is mainly to make the racing more entertaining, as well as placing the leading cars at the front of the line for the re-start.’
A further interesting element of IMSA regulations is that each team can listen to other teams’ radio communications between car and pit wall. This adds another strategical element to the picture because teams develop ‘codes’ to communicate with their drivers without showing their cards.
And if you’re thinking teams could just use scrambled radios, they are not allowed as IMSA wants the spectator to be able to listen to what the teams are saying as well.
Braun stresses how race strategy has to pivot around one, crucial point for a good result: the car must be on the lead lap at the last pit stop, even though IMSA regulations offer means to achieve this, even if you are one or more laps down.
‘This is the most important element during a race, and affects the strategy even more in the longer races. It’s what we work towards from the very start of the race. The fastest driver, who normally is in the car for the last part of the race, must be on the lead lap to have any chance to fight for victory.’
Rubber strategy
On the other hand, tyres are not normally a particular issue in IMSA, while they can be a decisive strategy element in WEC or ELMS.
‘IMSA give a tyre allocation for the whole weekend, from the first free practice to the end of the race, and we are free to use them the way we want,’ explains Braun. ‘Also, most of the classes only have one compound – sometimes even the same compound for the whole year – which takes away any strategic considerations with respect to tyre choice during the race.
‘The number of tyres we are allowed to use for a race is normally enough not to need to double stint any, with the exception of the longer races, where we usually had to double stint a couple of sets.
‘In those races, you can decide when you want to do that. For example, it could help to leave the car with worn, but warm tyres when a new driver jumps in, especially if it’s the non-professional driver and they haven’t driven for some hours. Being already warm, the tyres would have grip from the moment the car leaves the pit, which would give the driver confidence and help bring them up to their peak performance in a shorter space of time.’
The advantage any such choice might bring is difficult to quantify, but it’s still a strategic decision that has to be made.
Strategy can lead to some incredible results. Here Jon Bennett celebrates a race win with his co-driver Colin Braun, son of Jeff who called the races from the pitwall for the Core Autosport team
As the Weather Tech championship also has some pretty short races in its calendar, there are other situations where a team might decide not to change tyres at all during a race, or only change two of them.
‘I reckon in Detroit, where you normally do only one pit stop [in an hour and 40-minute race], some GTD teams stayed with the same set of tyres for the whole race, or only change the left ones, because the majority of corners are right handers. This surely compromised their performance, but made their pit stop significantly shorter and so put them out in front on a circuit where it is notoriously hard to overtake, even with the grip advantage of fresh tyres.’
Unforeseen events
Despite the effort teams put into preparing for races and trying to manage them the best possible way on track, they will still face issues that cannot be foreseen.
Braun remembers how CORE Autosport was frustrated in its attempt to secure LMP3 class victory during the 2021 Daytona 24 hours by a problem more connected to car design than to the team’s race preparation.
‘We had brakes issues during the whole race,’ he recalls. ‘The drivers complained that the car did not slow down effectively, and we could not understand why. The only thing we were left with was to stop the car and put on new brakes. This improved the situation for some time but, after about six hours, the problem presented again.
‘Of course, this ruined our race, but it wasn’t until the car returned to the workshop that we were able to figure out what the issue was. We were using the pedal box in its most forward mounting position and, when the pads became worn, the brake pedal was hitting the steering column, effectively preventing the drivers from braking.
‘In a normal situation, we would change the brakes on an LMP3 car only once during the 24 hours. IMSA even mandates one single eight-minute stop during the race, and this is when most teams take the opportunity to change the brakes, but in that particular race we found we had to change them every six hours!’
As annoying a that was, this is a good example of how sometimes teams have to decide whether to try and keep going or bring the car in for assessment and repair.
‘I always have a sheet that helps me make such decisions quickly, and it’s based on my whole endurance racing experience. I call it my stay out or fix sheet. In there, I have the time I think it would take to fix certain problems. I also consider the remaining race time, with intervals of 40 minutes. Based on all this information, I can look at the lap times to estimate how much a certain issue is costing us. This can be then put into a chart, taking into account how long the race still has to run and how much we would lose each lap. I can then compare it to see if the repair time could be recovered after a stop, thanks to a better pace, or not.
‘It is pretty simple, but it’s another example of how helpful it can be having something that tells you in a second in which direction to go, without the need for any complicated analysis in the heat of a race. It is not exactly a strategy item, but being prepared will always help.’
Next month, Jeff Braun shares further insight into specific pre-event work that helps handle the invariably stressful situations that occur during an endurance race.
