Fuel For Thought

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FUEL What’s quicker, a 335d or its petrol-powered equivalent? We put standard and tuned 335s through their paces at Bruntingthorpe Proving Ground to find out Words: Luke Wood Photos: Malcolm Griffiths/Max Earey

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Do you pay the premium for diesel power in your 335, with tons of torque and a greater range between fill-ups, or…

L

e Mans racers are doing it, Touring Cars are doing it and with the world the way it is at the moment it would come as little surprise if Formula 1 doesn’t follow suit in the not too distant future either.

It seems that diesel is taking over the world and it’s not just the race fraternity that’s benefiting either, because all the high-end technology that has worked so well to claim all those trophies is inevitably filtering down to the forecourts, and this means that it is no longer dull to have a D on the back of your car, but desirable instead. In fairness, BMW seems to have steered clear of going the way of the diesel with its motorsport programme, (although with SEAT doing so well in the WTCC with its Leon you have to wonder how long it will stick with the 320si) so in a way it’s surprising that it is leading the way in terms of producing the meanest and greenest diesel road cars on the planet. Engines such as the twin-turbo, four-cylinder unit in the 123d, the third generation 3.0-litre common rail in the facelift 330d and the mighty twin-turbo ’six that lives under the bonnet of almost all top end models in the BMW range are in a class of their own.

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Not only are they becoming increasingly refined but they manage to deliver a blend of performance, flexibility and economy that more often than not puts the petrol alternative to shame. The day of the dirty diesel is long gone and the agricultural horrors of the past are now just a distant memory.

But are diesels really the future and can they ever replace petrol powered cars as the default performance option? For most die-hard petrol heads, fast diesels are merely a way of making the daily commute marginally less painful and when they’re not being used mid-week they double up as loadluggers or cars that are handy for towing something lightweight and high-revving to a trackday.

These are the kind of people that BMW is going to find hardest to convince that torque, not brake horsepower, is the way forward and while this might take some doing, we feel that the time has come to at least start considering the possibility.

Which would you say is the most potent car for example, the 335i with 306hp and 295lb ft or the 335d with 286hp and 420lb ft? Both have sixcylinders, a brace of turbos, near identical capacity and a top speed that is limited to 155mph and both

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335BATTLE …do you go down the petrol route, with more revs, a manual gearbox and a proper soundtrack from the twin-turbo ’six?

have the ability to see off the sprint to 60mph in under six-seconds. The way they go about it though is quite different, with the 335i relying on a broad spread of revs to muster its performance and the 335d leaning on a mountain of torque that threatens to rip the run-flats from the rims at just 1750rpm.

Under everyday conditions, it’s very easy to be swayed by the character of the petrol model. There’s the option of a six-speed manual gearbox for a start, something that is usually high on the wish list of the more enthusiastic driver, but it’s the engine note that really helps to sway things. The latest engines are getting better, but noise is the diesel’s perennial problem. Let’s face it, when was the last time you wound down the window in a tunnel to soak up the soundtrack from a 320d – hmmm, clattery.

If you can learn to live with this however, then the gap in performance is actually very small and in terms of real world driving the diesel’s torque counts for a lot. The sprint to 60mph looks good on paper but being able to overtake three lorries and a tractor as quickly as possible is sometimes more relevant.

All of which brings us to Bruntinghtorpe Proving Ground for a 335 showdown to end all showdowns,

an opportunity to see whether diesel or petrol packs the biggest punch in a straight line dash to 100mph, which is most effective when accelerating from 60mph to 100mph and, as a bonus, which is the quickest over a lap of a circuit.

To make things interesting we’ve decided to mix it up a little by including a selection of readers’ cars to run alongside our pair of press vehicles and to really add some spice we’ve invited along a tuned example of each to see how much can be gained from a remapped ECU. It may not be everybody’s cup of tea, but both the petrol and diesel 335 have huge potential hidden away inside their electronics and by tapping into the ECU you can expect large gains to be had in both BHP and torque. Companies such as Evolve Automotive for instance offer just such a service, unearthing an additional 54bhp and 59lb ft in the 335i and a further 44bhp and 73lb ft in the 335d for £1000 and £599 respectively. It’s a simple and painless modification carried out via the OBD port and in addition to being undetectable, it comes with full warranty cover as well.

Before we get to these though, we take our time to set some benchmark figures in the press cars, and

For most die-hard petrol heads, fast diesels are merely a way of making the daily commute marginally less painful

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Not only is it staggering to find such pace lower down the 3 Series range, but an impressive opening salvo toward the diesel camp as well

are immediately taken aback at just how conservative BMW has been with its official statistics. Storming off the line to 60mph in 5.1 seconds, our manual 335i obliterated the quoted 5.5-second to 62mph time and took just 7.4 seconds more to crack the ton.

These numbers are normally the reserve of M cars, so not only is it staggering to find such pace lower down the 3-Series range but a worryingly impressive opening salvo toward the diesel camp as well.

In response the 335d thunders up Bruntingthorpe’s runway in an incredible 5.7 seconds, again significantly quicker than the officially quoted time, before blitzing the 100mph barrier in 13.7 seconds dead. Fast, hugely so for a diesel, but not quite fast enough and it’s first blood to the petrol posse.

Round two and it’s the turn of our brave readers, all of whom have volunteered their personal cars to be launched into the fray. First up is John Gray, who keenly hands over the fob to his 335i Touring, a wagon that is used daily for work and used hard. In

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the short time he’s had the car John has put three years of mileage on the clock and is already on his second set of turbos, so if this doesn’t count as a well run-in example then nothing will. Run in it may be, but it also proved particularly difficult to launch cleanly and after several aborted runs we decided that the clutch had probably had enough so we decided to call it a day at 5.6 to 60mph and 13.6 to 100mph. Not bad for a miley workhorse, and pretty much bang on the manufacturer quotes as well, but try as we might we just couldn’t match the ballistic performance of the press car.

In contrast, the 335d of Kevin West actually managed to raise the game for team diesel, posting a stonking 0-60mph of 5.6-seconds, equal to the Touring and a tenth better than we managed with the 335d press car. By 100mph though, Kevin’s car was really on the boil. With a 13.3-seconds flyer it proved to be faster still than the press car and most importantly, three tenths faster than the 335i.

With the scores levelled it was down to the Evolve tuned bad boys to slug it out for the third and final round. With something in the region of 350bhp and 350lb ft of torque on tap the deciding factor here was how easy it was going to be to launch Chris Burridge’s car without frying the transmission or evaporating the rear tyres, so it was perhaps not too surprising that the initial 0-60mph did not quite match the earlier benchmark set by the press car.

Once on the move though and with traction less of an issue, the Evolve 335i really came into its own and by 100mph it was almost a second ahead.

With a seemingly impossible target to beat the Evolve 335d of Julian Marshall was lined up. With almost 500lb ft of torque at its disposal the big question again was just how effectively the standard differential, tyres and gearbox were going to be able to cope. Several techniques were employed in order to get the 335d off the line in the most effective manner, including holding the car on the brakes with

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Our readers are a brave bunch. Not only did they volunteer their cars but they allowed them to be abused by the Deputy Editor.

Above and beyond, gentlemen…

various amounts of revs dialled in, semi-auto launches, full automatic launches, launching without any holding on the brakes – all of which made some, but not much difference to the final outcome.

Which was that while the tuned 335d was monstrously fast to 100mph, nearly a second and half more than the quickest of the standard cars, it still didn’t quite have enough to outdo its petrol powered rival. With these last two cars we’re talking about a mere tenth of a second in places, and while that may not seem like much, it’s enough to make the difference between coming first and second. So that’s settled then, diesels may be getting close, but petrol is still the way to go, whether it’s in standard form or a more highly tuned state. Not quite, because the 335d has one last trick up its sleeve.

While the straight line figures of the standard versus Evolve tuned 335s are certainly revealing, there’s a limit to the amount of abuse we’re willing to inflict on our readers’ cars. We’re a caring bunch

The pros and cons of both the 335d and 335i were discussed at length. Actually, we were just talking about what to have for lunch

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of individuals you see, and when we invite people along to places like Bruntingthorpe, we like to see them leave at the end of the day with all the important bits of their vehicles still attached.

So in the interest of science, we thought we’d give the press cars one last workout by driving them flat out around a circuit, somewhere with fast straights, challenging corners and not too much to hit should it go wrong, to see which would set the fastest lap.

Conveniently, our sister magazine Performance Car happens to have just such a track laid out at Bruntingthorpe Proving Ground and as those boys are always willing to throw caution to the wind in the search of a hot lap, we handed over the key fobs to its chief Stig, Deputy Editor Chris Knapman, to see how the two hot 3 Series would fair.

Positioned in our makeshift pitstop, bets were made as to which would be the quickest of the two, the torque happy Derv demon, or the silky smooth petrol and as the latter was armed with a ‘proper’ manual six-speed it’s fair to say that the 335i was the initial odds-on favourite. And, after the first flying laps it certainly seemed as though the diesel was going to have its work cut out as the singing straight-six roared

Short shift up one gear then flat through seven.

335d’s torque really starts to show

5 4

6

its way around the vast open spaces of the Leicester Proving Ground, picking up huge speed on the long, flat straight and flinging itself into the fast bends with tyre screaming conviction. The 335d, handicapped by its slush ’box would have no chance. Imagine our surprise then when the results were downloaded from the timing gear. We checked, we double checked and we checked again but there was no getting away from the truth of it. The diesel had won by just 1/10th of a second, and again it was all down to its prodigious twist. According to Knapman there was nothing in it under braking and in corner entry, it was just that the 335d had so much more shove on the exit. So there you have it, 1m 22.8seconds for the 335i and 1m 22.7 for the 335d.

Diesel wins, petrol loses. And what is more incredible is that this winning time is only 2.4-seconds shy of the 1m 20.3s that Performance Car recorded for the E90 M3, in similar conditions earlier in the year.

Should we start worrying about a diesel powered M car in the future? You heard it here first… ●

0-10 0-20 0-30 0-40 0-50 0-60 0-70 0-80 0-90 0-100

335i* 0.7 1.4 2.1 3.2 4.0 5.1 6.8 8.4 10.2 12.5

335d* 0.6 1.3 2.2 3.1 4.2 5.7 7.2 9.1 11.2 13.7

335i 0.6 1.3 2.1 2.9 4.4 5.6 7.7 9.3 11.2 13.6

335i** 0.8 1.7 2.3 3.0 4.2 5.2 6.4 8.4 10.0 11.7

335d 0.5 1.2 2.0 3.0 4.1 5.6 7.0 8.9 10.9 13.3

335d** 0.6 1.3 2.1 3.0 3.9 5.3 6.5 8.1 9.9 11.9

CONTACT: Evolve Automotive

60-100

7.4

8.0

8.0

6.5

7.7

6.6

Tel: 0870 0850 111 Web: www.evolveyourcar.com

* Press car

PERFORMANCE FIGURES

** Evolve tuned car

Both cars excellent on the brakes, but again 335d has more punch on exit

7 Balance throttle here, extra weight in diesel’s nose not obvious

START/FINISH

3 3rd gear in 335i, 4th in 335d

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335i’s manual ‘box more satisfying to use than diesel’s autobox but still no quicker

Turn in almost flat and hold tight. Both cars equal here

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8 9

Small slide into nine. 335d slides as well as 335i

Turn in slowly, wait to pass apex before getting on the power to the finish Lap times: 335d 1 minute 22.7 seconds 335i 1 minute 22.8 seconds

CHRIS SAYS: 335i felt faster but the 335d’s torque was astonishing