Porsche back in Le Mans!

[Pierce89]

You can get a bit more fuel if you choose the smallest of the four hybrid systems. You can have 2,4,6 and 8 MJ electric systems and you can have them on front and rear wheels.
I reckon that the 4 and 6 MJ systems will be the most popular.

Bart Hayden from Rebellion was interviewed just recently about their 2014 car. He said that only the most powerful electric system would make sense from performance point of view. He ofcourse might have his reasons to say that, because Rebellion wont be using (cant afford?) hybrids next year.

I thought the fuel was supposedly balanced to make each option equal.

Off topic: Any thoughts on electric turbo compounding, but without F1's stupid requirement that turbo and compressor be on the same shaft?

[xpensive]

I do not understand your reasoning. If the small turbo is more efficient it will simply make more hp out of the limited fuel supply. Both engines will have the same fuel flow available. And if the 4-cylinder makes more power the car will have higher performance. How will you escape from that dilemma? Higher performance and potentially shorter refuelling stops will all favour the more efficient engine, which is not likely to be your V8.

There are two things bothering me here WB.

- First of all, with the flow-limit, I'm not entirely certain that a small high-revving engine will be advantageous on all counts to a lower-revving V8, as a tribologist, I know that shear-forces on the oil-film goes with the square to the speed.

- As this is sportscar racing, I find it difficult to believe that the final rules will force all manufacturers into I4s, imagine Ferrari, Lamborghini, Jaguar and Aston Martin with such engines?

[Tommy Cookers]

if I understand correctly .......
for LM 5 stroke engines are illegal, except when the 5th stroke is via a turbine and electrical generator
(and more-complete expansion 4 strokes eg with Honda patents are also illegal)
the fuelling rate to the heat engine is strictly limited when propulsion is desired, but effectively free at other times
so the heat engine cannot accumulate fuel, but fuel can be freely used for accumulation of electrical energy
(by fuelling above zero under braking, while electrical generation is drawing energy from the pool of KE and motor energy)
the issue of whether to limit fuel by rate or by quantity has been rather ducked
so LM will be like F1, but Ecclestone-free ?

F1 does have fuelling fixed at 10500 rpm, this is what makes 6 or even 4 cylinders viable
the traditional view is that smaller cylinders allows higher CR and so help TE (although ME tends lower)
while the super new DI has in principle benefits for all cylinder sizes and engine types
it is (for now anyway) limited in its rpm capability

I rather like electric turbo compounding via the F1 mandated arrangement
giving in road use the wider power band characteristic of the NA engine (by electrically driving the turbo when exhaust is insufficient)
for normal road cars one could to this end mechanically drive a centrifugal supercharger via an motor/generator
this would allow modulation of supercharger speed to match the engine's needs better than the turbocharger can
but F1 has chosen to make a 'bolt on' change that will be commercially easier to emulate eg in premium road cars
turbo-compounding always was done this way, by 'bolting on' extra parts on the assembly line

btw 'flat' engines are always 180 deg Vs if they have more than 8 cylinders ie a 917 has 7 main bearings, a 908 has 9
but if you have the closer bore spacing that liquid cooling allows your 12 cyl (Ferrari 312 etc) 180 deg V needs only 4 main bearings
and a Mr Anderson made in the 1950s an F2 'flat' (ie a 180 deg V) 8 that had only 2 main bearings

[WhiteBlue]

There's always the chance larger motors will be more efficient from revving much lower and creating less friction, but obviously more cylinders will create more friction so its a trade off.

If this was true we cannot see it in the real world. Why is everybody and his dog downsizing the engines for fewer cylinders then? There must be an efficiency advantage in it which I believe comes from reduced friction and reduced heat losses. And let us not forget the lesson we learned about turbo racing engines in the eighties from F1. The engines with fewer cylinders like V6 and I4 were the winners.

[WhiteBlue]

First of all, with the flow-limit, I'm not entirely certain that a small high-revving engine will be advantageous on all counts to a lower-revving V8, as a tribologist, I know that shear-forces on the oil-film goes with the square to the speed.

I'm thinking that a small high boost turbo and a big mild boost turbo will probably run at very similar revs. The most efficient injection and combustion technology requires them all to run low revs. So they will all want the revs to come down and turbo boost is the weapon they both have available. The small engine will simply boost 1.5 or 2 times higher than your mild boosted V8. To me the V8s, V10s and V12 only have a use if you ban the turbo. The moment you have freedom to exploit the benefits of forced induction high cylinder counts become a burden. Nothing beyond six makes any sense to me if your goal is efficiency.

As this is sportscar racing, I find it difficult to believe that the final rules will force all manufacturers into I4s, imagine Ferrari, Lamborghini, Jaguar and Aston Martin with such engines?

If you read the ACO document you see that they are not aiming for those manufacturers. They want the road car manufacturers that make cars for the man on the street. If they get the DTM/GT500 bunch as it sounds likely from the reports they would have: Mercedes, Audi, Porsche, Toyota, BMW, Honda and Nissan. I think there is plenty of potential in that list and they all would be happy with a 2L 4-cyl engine as they are committed to run them from 2015/16 in DTM/GT500 in Europe, Japan and America. It sounds like a very powerful plan to me. The auto industry could go back to running all their developments aimed for the road in an endurance racing series. It would be a wet dream for the strategists. The money spend would generate useful technology and would advertise the brand at the same time. Hardly a dumb concept. It would not suit Ferrari but Ferrari are not the measure of all things. They got F1 to commit to V6 against the desire of all other manufacturers. I doubt that the other guys will let it happen again.

[Pierce89]

There's always the chance larger motors will be more efficient from revving much lower and creating less friction, but obviously more cylinders will create more friction so its a trade off.

If this was true we cannot see it in the real world. Why is everybody and his dog downsizing the engines for fewer cylinders then? There must be an efficiency advantage in it which I believe comes from reduced friction and reduced heat losses. And let us not forget the lesson we learned about turbo racing engines in the eighties from F1. The engines with fewer cylinders like V6 and I4 were the winners.

As I said, its a trade off. Sometimes, in race conditions a larger lower revving motor can be more efficient than a smaller higher revving motor. Reduced surface area reduces friction, but so does lower rpm's.A couple years ago, in ALMS ,Porsche lobbied to have the Corvette's fuel capacity reduced because its 5.5L v8 got better fuel mileage than Porsche's 4L flat6.

There are always tradeoffs. If they can raise boost enough to negate the need to rev higher, the smaller motor will probably be more efficient, but on equal boost a 3L v6 can be more efficient than a higher revving 2L I4 in race conditions.

Overall, I'm only saying I don't agree with the notion that all manufacturers will automatically go with tiny I4's without doing a lot of research first. I will agree though, that with unlimited boost the 4 cyl will win out. I just know the FIA has a tendency to limit boost in the long run, regardless of original intentions.

[Pierce89]

It would not suit Ferrari but Ferrari are not the measure of all things. They got F1 to commit to V6 against the desire of all other manufacturers. I doubt that the other guys will let it happen again.

This is not completely true as your beloved Mercedes also wanted the v6's.

[xpensive]

...
They want the road car manufacturers that make cars for the man on the street. If they get the DTM/GT500 bunch as it sounds likely from the reports they would have: Mercedes, Audi, Porsche, Toyota, BMW, Honda and Nissan. I think there is plenty of potential in that list and they all would be happy with a 2L 4-cyl engine as they are committed to run them from 2015/16 in DTM/GT500 in Europe, Japan and America. It sounds like a very powerful plan to me.
...

I don't know how many Porsche models are intended for "the man on the street"?

But anyway, it would be sad indeed if your predictions are correct, sad and xtremely boooring, like today's F1 but worse.

I hope that MrT realizes this before the last reasonably technically free racing-class is turned into yet another IRL.

[WhiteBlue]

If they can raise boost enough to negate the need to rev higher, the smaller motor will probably be more efficient, but on equal boost a 3L v6 can be more efficient than a higher revving 2L I4 in race conditions.

Overall, I'm only saying I don't agree with the notion that all manufacturers will automatically go with tiny I4's without doing a lot of research first. I will agree though, that with unlimited boost the 4 cyl will win out. I just know the FIA has a tendency to limit boost in the long run, regardless of original intentions.

The boost was specified at 4 bar in the new 2014 formula AFAIK. I don't think that the ACO will change something that fundamental after the development race has already run for 12 months. They surely work hard not to piss off any manufacturers. That is enough boost for the small engines to allow them low enough revs IMO.

I don't know how many Porsche models are intended for "the man on the street"?

Probably a lot more than Ferraris.

This is not completely true as your beloved Mercedes also wanted the v6's.

Not completely true either. Mercedes accepted the 2013 formula. When Ecclestone and Ferrari shot it down they changed over to the other camp. There are enough quotes by Mercedes and Haug saying they supported the 2013 plan of the FiA. You can believe me that Ferrari were at the heart of the battle against the 4-cylinder engine. Mercedes are not very particular over that question. They also support the future 4-cyl format in DTM.

As a side issue I have converted the volumetric fuel flow rate into a mass flow rate using 0.7396 kg/L for E10 petrol as specific weight. I arrive at 23.2 g/s for a 6MJ equipped factory car. That is substantially less than F1 allows them (27.8 g/s). F1 will have almost 20% more fuel flow than LMP1 will have next year. I think the consequences are obvious.

[gixxer_drew]

I don't think they blame it. It is simply true that F1 aerodynamics are useless for a sports car manufacturer. ..... If you can only win by arcane aerodynamics .

LMP performance is virtually as aero dependent as F1. Any vehicle with these levels of downforce will have aero as the main performance differentiator.

I do not have anything against aerodynamics. But in F1 they absorb too much of the development money. This is not the case in LMP1. They also do a lot of engine and power train developmen which is useful for a sports car manufacturer. Ferrari have complained about this for a long time but they cannot get the rules they want against the chassis constructors.

But you simply cannot do anything about this, F1 is the example of how regulation cannot put that genie back in the bottle. There is much power to be harnessed in the motion of the medium,every other technology on a modern car is in a later phase of the development curve so new ideas are less increment in performance. Even spec body has proved totally ineffective at limiting aerodynamic dependance. I think the only way to make aero less of a factor is to reduce the rules on it, let it develop quickly to the higher end of the curve. Good ideas are cheap, super high accuracy wind tunnels are not. I would argue the rules have actually increased cost dependance on aerodynamics for this reason. A great new concept needs an idea and a half decent tunnel. Optimizing 1% better end plate inside of a rules box needs millions of dollars. The lap time dependance on aero has everything to do with the delta between maximum potential and current state of the art. The only other option is to start racing on the moon or make the whole car so much slower that the air speed is useless.

[WhiteBlue]

I think the only way to make aero less of a factor is to reduce the rules on it, let it develop quickly to the higher end of the curve.

The source that analysed different engine and aero configurations said that engine efficiency in LMP1 will outscore aerodynamics or downforce. I'm happy to wait and see who will be right at the end.

[gixxer_drew]

I think the only way to make aero less of a factor is to reduce the rules on it, let it develop quickly to the higher end of the curve.

It looks like you haven't read the sources cited in this thread. Analysis of the rules state that engine efficiency in LMP1 will outscore aerodynamics or downforce. I'm happy to wait and see who will be right at the end.

I read them, thanks. Regardless of what conclusions you might have drawn from them I was speaking in reference to a broader scope than just Le Mans.

[matt21]

As the ACo as specified a fuel consumption per lap, I´m wondering if this is based on a fixed lap length (e.g. one lap in Le Mans) or if it the same fuel allowance on any circuit which would give different power on different circuits.

I really don´t understand why they are not using a fuel allocation per race distance like in the old Group C days or a fuel flow like in F1 (per hour).

[WhiteBlue]

As the ACo as specified a fuel consumption per lap, I´m wondering if this is based on a fixed lap length (e.g. one lap in Le Mans) or if it the same fuel allowance on any circuit which would give different power on different circuits.

I really don´t understand why they are not using a fuel allocation per race distance like in the old Group C days or a fuel flow like in F1 (per hour).

The fuel flow can only be controlled by a mass flow or volumetric flow figure. The ACO started with a per lap figure because they have data on the consumption. One has to assume that those per lap figures at Le Mans will be converted into mass flow when they apply it to a control mechanism with sensors and actuators.

In the publication it says that fuel allocation per race distance would lead to economy runs and ruin races. Mass flow is the better way to control it.

[matt21]

Were there economy runs in Group C? Sauber for example had 200 liters left in Le Mans 1989, despite winning.

For me, the mass flow is only a method to limit power levels, not to enhance economy.