Sebring 12 Hours: The amazing Audi R15 up close and uncovered ...

[LeonOfTheDead]

Leon, should Audi switching from a 5.5L V12 to a 5.5L V10 give the engine even more torque due to a presumably bigger bore? I'd imagine peak power may suffer a bit but torque should be up right? Speaking in rough terms of course.

in diesel engines the relationship between the bore and the decaying of the flame front is basically irrelevant. think of ships' diesel engines, with an unitarian displacement up to 2.000 liters or maybe even more.
that's because the high pressure and the lack of a definite starting point for the flame allows for a better flame/detonation front distribution and propagation.
Supposedly though, with 10 cylinders instead of 12 the engine, considering the same displacement and all the other parameters (like the same bore/stroke ratio), should produce 0.94 times the power of the 12 cylinder one, while rotating at a 0.88 times lower speed.

assuming these completely theoretical calculations as a reference, the engine with 10 cylinders would have less power, lower max rpm, and therefore less torque too.

[RacingManiac]

about that, I would say the stress could be still relevant due to thicker components in a diesel engine, therefore higher masses even for rotating components. still it's the rotating speed the main issue, and I doubt the mass is so much higher to balance the effect.
the Audi engine should be heavier than the Judd to equal the safety due to the higher stress generated by the diesel combustion process, so even considering an equal stress but an higher weight the torque is likely going to be give the Audi a better overall performance, regardless of 20 hp gap in power, if that's the case.

I have no doubt that the Judd is lighter, but I think as you said the overall benefit is probably bias toward the Audi just because of the extra flexibility afforded by the Audi. Though I don't think the Audi is as heavy as one might imagined, since from the very beginning of their diesel program they are claiming the specified mass per cylinder the 5.5l V12 is the same as the R8's 3.6l V8. And that the V10 is the same as the V12.....mind you, the Judd still saves on the lack of plumbing over the twin-turbo diesel....

The higher and likely much flatter torque curve also translate to probably better power in ALL rpm range, even if the Judd might make the same peak power. Remember that the torque characteristic was flexible enough that they were able to eliminate a gear...

[henk4]

The higher and likely much flatter torque curve also translate to probably better power in ALL rpm range, even if the Judd might make the same peak power. Remember that the torque characteristic was flexible enough that they were able to eliminate a gear...

The point is that the Judd makes considerably more peak power than the figure now quoted for Audi. I think Henri P. said that he had at least 650. (When the ACO said that diesel power should be reduced by 10% he mentioned that that would going down from 750 to 675 and the diesel would still have more peak power.

[LeonOfTheDead]

I have no doubt that the Judd is lighter, but I think as you said the overall benefit is probably bias toward the Audi just because of the extra flexibility afforded by the Audi. Though I don't think the Audi is as heavy as one might imagined, since from the very beginning of their diesel program they are claiming the specified mass per cylinder the 5.5l V12 is the same as the R8's 3.6l V8. And that the V10 is the same as the V12.....mind you, the Judd still saves on the lack of plumbing over the twin-turbo diesel....

The higher and likely much flatter torque curve also translate to probably better power in ALL rpm range, even if the Judd might make the same peak power. Remember that the torque characteristic was flexible enough that they were able to eliminate a gear...

exactly. I guess also that Judd couldn't put the same effort/money in their engine as Audi did, just considering this is their second diesel engine in three years.
if this was F1 or whatever apart from endurance racing, more power and a lighter engine (assuming that if Audi was to produce also a petrol engine for the R15 it would result being lighter) would have been the way to go, but in such races this solution and its flexibility are the package to beat.
a small gap in hp at the peak, a lot more torque and a more relaxed torque/power curve, a solid engine and gearbox package. it's all about reliability, so your performance has to be much better if you count to beat them (ask Peugeot ).
Wondering how AM/Lola will perform at Le Mans.

[LeonOfTheDead]

The point is that the Judd makes considerably more peak power than the figure now quoted for Audi. I think Henri P. said that he had at least 650. (When the ACO said that diesel power should be reduced by 10% he mentioned that that would going down from 750 to 675 and the diesel would still have more peak power.

if you consider my calculations (and so you don't consider all the technical improvement the new engine might benefit) the power of the new Audi V10 should be about 45 lower than that of the V12 one, assuming that 750 hp figures is correct. now apply the 10% reduction and you obtain a 635 hp figure.

[henk4]

if you consider my calculations (and so you don't consider all the technical improvement the new engine might benefit) the power of the new Audi V10 should be about 45 lower than that of the V12 one, assuming that 750 hp figures is correct. now apply the 10% reduction and you obtain a 635 hp figure.

already more than 6% more than the 600 quoted

[Ferrer]

Hm...all the advantages that I am trying to sell in my never ending discussions about diesel engines in normal road cars...
Obviously a suitable gearbox cannot compensate the relative absence of torque in a petrol engine...

A more fair comparison would be with a turbo/supercharged engine.

Either that or a normally aspirated diesel...

[RacingManiac]

The point is that the Judd makes considerably more peak power than the figure now quoted for Audi. I think Henri P. said that he had at least 650. (When the ACO said that diesel power should be reduced by 10% he mentioned that that would going down from 750 to 675 and the diesel would still have more peak power.

That's still a "peak" power, and in petrol engine's case it would really be a peak, especially Judd is still not a direct injection motor, were you can recover a lot of the torque by fine tuning your AFR for specific rpm at the combustion level. Its the same reason why Judd keep bumping the displacement of their motor trying to get the same power at a lower rpm and better torque curve. Acura is quoting 650bhp for their 4 liter, but its going to be a hard working engine because of their displacement disadvantage....

I really admire Audi's program, because their engineer must be learning a ton from designing something like this....

[henk4]

I really admire Audi's program, because their engineer must be learning a ton from designing something like this....

and we'll get to see the results of such experiences in our road cars too.....

[LeonOfTheDead]

already more than 6% more than the 600 quoted

consider we are talking about the same (parent) comany producing the Veyron with 1060 and more hp to be sure to have the 1001 they promoted. that's still a 6% difference

and we'll get to see the results of such experiences in our road cars too.....

or maybe it will be too late with the new small displacement variable geometry turboed direct injection engined petrol cars being even better, who knows?!

[henk4]

or maybe it will be too late with the new small displacement variable geometry turboed direct injection engined petrol cars being even better, who knows?!

you forgot the variable compression ratio....

[LeonOfTheDead]

you forgot the variable compression ratio....

why not the diesotto too so?!

by that time, we are all going to commute with segways

[henk4]

A more fair comparison would be with a turbo/supercharged engine.

funny that you should say that, because the LMP1 regulations allow such engines.....and yet nobody is using them.

[henk4]

why not the diesotto too so?!

by that time, we are all going to commute with segways

bicycles are the vehicles of the future.....and diesotto is variable compression ratio....

[LeonOfTheDead]

bicycles are the vehicles of the future.....and diesotto is variable compression ratio....

the main aspect of a diesotto is the combustion of petrol without a spark. There are other concepts of regular petrol engines (meaning with sparks woring all the time) with a variable compression ratio.

(my bicycle does about 10 km per day regardless of what I eat, so it's quite frugal I must admit).