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Le Mans recharged - Developments in the top flight of sportscar racing

Published by Pat W

The fuss made in Formula 1 about the new-for-2014 power units is well-documented. Flying somewhat under the radar are the developments in sportscar racing, the LMP1 class at Le Mans and in the FIA World Endurance Championship. In the week of the great race itself, just what is going on?

Class acts

LMP1, the top class for the fastest most advanced sports-prototypes, has been split into two sub-classes for 2014. The big factory teams of Audi, Toyota and now Porsche have been compelled to enter the new LMP1-H or 'Hybrid' class.

No. 14 Porsche leaves pit lane during the Le Mans test day
Credit: Porsche Cars

As it is important to look after the smaller privateer teams who can't afford to develop hybrid technology, they may enter the new LMP1-L or 'Light' class in which both factory teams and hybrids are not permitted. In practice only Rebellion Racing have entered LMP1-L so far this year, though more cars are promised from other teams.

With both sub-classes the aim is to promote efficiency. Compared to 2013, this year's cars are 100mm narrower in a bid to reduce downforce and they run on narrower tyres. Cornering speeds are consequently reduced but the significantly reduced drag, combined with the sheer effectiveness of the hybrid systems and their traction, means top speeds are higher than before. Remarkably, laptimes at Silverstone and Spa were comparable to last year despite less downforce, less grip, less fuel. Such is progress!

Fuels and horses

Much like Formula 1 there is a fuel flow limit. What is the fuel flow limit? Well that depends how powerful your hybrid system is and what fuel you are using! More on that in a minute.

Cars have been balanced on fuel flow only. There are no engine air restrictors and there are no limits on turbo boost pressure

One important thing to note is that in F1 you are not allowed to exceed this fuel flow on any lap. In the WEC including Le Mans it is a rolling 3-lap average, so if you exceed the limit on a given lap that's okay so long as you recover it by driving more carefully on the next two laps to reduce your average.

You only attract a penalty if your 3-lap average is over the limit. Nobody has been hit with a penalty yet this year.

The cars have been balanced on fuel flow only. There are no engine air restrictors any more, and there are no limits on turbo boost pressure. You can use any engine size you like in LMP1-H, and up to 5.5 litres in LMP1-L.

The road to recovery

This is where things get really interesting! In F1 the hybrid systems are the same for each team. They or their suppliers are allowed to make their own rather than buying it off the shelf, but ultimately they all follow the same layout.

That is not the case in LMP1 where teams are free to use all kinds of solutions. The most exciting thing? All three factory teams have chosen a different route!

Fässler, Lotterer and Tréluyer in Spa
Credit: Audi AG

Before we look at what each team has chosen, first we must understand there are four 'divisions' of hybrid based on the amount of energy they can recover and deploy per lap. Following on from that, the more you can recover through your ERS, the lower your fuel flow limit in kg/hour. The divisions (calculated per lap of Le Mans) are:

  • Up to 2MJ
  • Up to 4MJ
  • Up to 6MJ
  • Up to 8MJ

The technical regulations are public and you can look up the fuel flow rates in Appendix B or I recreate them below. Alternatively Paul Truswell of Radio Le Mans has taken a look too.

Fuel flow per lap
DivisionPetrol (kg/hr)Diesel (kg/hr)
With no ERS102.984.6
F1 (for comparison)100

Let's distill this down into a simple question: Is your hybrid system good enough to overcome a lower fuel flow limit per lap, compared with someone using more fuel and a less powerful ERS?

Toyota and Porsche are betting theirs are good enough, they have decided to enter their systems into the 6MJ section with petrol fuel. In fact they seem to have played it safe, many were betting one or both would go all the way to 8MJ straight away.

Audi has gone conservative with a 2MJ system and a diesel engine, which took people by surprise because it was expected they'd run a more powerful ERS.

You can see the future laid out before us - the FIA & ACO have not announced anything yet but you can see they might one day mandate 2MJ as the lowest division, and 4MJ a year or two after that, and keep ratcheting it up every year to encourage development. You can also see how that despite being an efficiency formula based on fuel, these races are not fuel-saving eco runs. The hybrid systems see to that.

Finally, with the previous generation of hybrids there were rules preventing the ERS being used below 100km/h and only recharging in certain defined zones on the track - both of those rules are deleted, you can now both deploy and recover the ERS whenever and wherever you like.

So who's got the power?

2014 Formula 1

Engine1.6 litre turbo V6
HybridKinetic energy recovered from the rear axle, with a second system recovering heat from exhaust gases
Energy storageBatteries

I don't know what type of batteries are used. I understand flywheels are legal but nobody uses them.

Audi R18 e-tron quattro

Engine4.0 litre turbo V6
HybridKinetic energy recovered from the front axle
Energy storageFlywheel from Williams Hybrid Power
Hybrid class2MJ per lap

Audi chose a smaller hybrid and a bigger engine than their competitors, choosing to refine the concept of their previous car rather than go for something completely new. They say it is better to have a smaller and lighter hybrid system, claiming the weight saved offsets the benefits of a bigger system. As of the first two rounds of the WEC this has yet to be proven correct. Audi may have one thing going for them: Their system is possibly less complex than those of their rivals, isn't too different to what they've been running for the past couple of years. With less to go wrong and already understanding the foibles, they could win this race on reliability, not speed.

Toyota TS040 Hybrid

Engine3.7 litre normally aspirated V8
HybridKinetic energy recovered from both front and rear axles
Energy storageSuper-capacitor
Hybrid class6MJ per lap

Toyota are regarded as the leaders of hybrid technology, not just on the road but on the track and they are out to prove it here, with a big ERS and a slightly smaller engine than Audi but normally aspirated rather than turbo. Recovering and reusing energy on both axles gives them a big advantage over Audi's single axle.

The super-capacitor is interesting. We learned at Spa that a super-capacitor is capable of being recharged much faster than Porsche's lithium-ion batteries, as fast as it deploys it can be recharged again. And it deploys very quickly - Toyota actually claim that with engine and ERS on full throttle they are making 1000bhp!

Disadvantage? It means when you use it, you use it up very quickly so you can't spread the charge around the lap. Toyota says this doesn't matter because it recharges so quickly that after the next big braking zone you'll have full boost soon anyway.

Porsche 919 Hybrid

Engine2.0 litre turbo V4
HybridKinetic energy recovered from the front axles as well as exhaust gases driving a turbine
Energy storageLithium-ion batteries
Hybrid class6MJ per lap

Porsche has chosen the opposite route of Audi. They've taken a much smaller engine, just a little 2 litre V4, and a big ERS. It has the same capacity and power as Toyota's ERS but the lithium-ion batteries are slower to deploy and slower to recharge - a deliberate decision by Porsche to allow them to carry the charge around the lap and use it where they want to.

The one question mark about this car is reliability, with a car failure at Silverstone and troubles with the other one at Spa there are questions about how far these cars will go. But it is only year one.

Playing favourites

TS040 Hybrid completes scrutineering.jpg
Credit: Toyota Europe

At Le Mans the smart money is on Toyota and I can't argue with that. I can't call a car (I'd love it to be Davidson). The second favourite is Audi who have three cars to play with this week. I struggle to see Porsche staying in contention for the whole race but I tell you what they'll be competitive while they last.

In the WEC, Toyota already has a handy points lead and it is difficult to see them losing it!

I recommend listening to the Radio Le Mans podcast Toyota Tech Talk Series 2 Episode 2. It is 26 minutes of Anthony Davidson talking to John Hindhaugh about hybrids, super-capacitors, ERS, and all the new tricks they have available with brake-by-wire - and it is very, very interesting.

These rules have proven attractive to manufacturers. Nissan have already made an announcement, they are building an LMP1-H car for 2015. This promises to be hugely exciting, imagine four teams! In the meantime Nissan are at Le Mans this year with a 'Garage 56' entry called the Nissan ZEOD RC. It looks like a Delta Wing but that's the end of the similarities. It runs a tiny 1.5 litre, 3-cylinder turbo producing 400 hp and its ERS recovers enough energy that the stated aim this weekend is to run an entire lap of Le Mans on electric power only. And not only that but to do so for one lap in each and every fuel stint.

Finally, there is a buzz about Le Mans - there is another announcement due on Saturday that was meant to have been made a few weeks ago and was deliberately held back to race day. Some say it is Ferrari, others say Ford, still more say Honda. Who will it be? I have no idea and cannot wait to find out.

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