File this under spurious rumor for now (though note where you heard it!). But it is with enough detail and from a reliable source that I felt justified in publishing it as there is a large information void regarding the subject of the new Audi LMP car. Word is that the car will be diesel V12 powered. It is no secret that Audi is coming back with a new car that will be diesel powered. But up until now all talk had centered around a V10 turbo diesel. My source, who knows better than I, indicates that a move to a V12, "reveals that they are after the maximum allowed volume and/or the highest possible revs in the diesel." Simplified, diesels generate power by increasing boost pressure or throwing more fuel into the cylinder. Both of these methods increase the likelihood that the head will separate from the block and aren't necessarily conducive to endurance racing reliability. A V12 will allow for more revs which, while not eliminating reliability issues, moves the stress on the engine from the head bolts to elsewhere (the cylinder heads will be under enough stress as it is!).
And while we're at it, why diesels anyway? Again, simplified, with the regulations pegging engine power to around 650 via the engine inlet restrictor, few gains (if any can) be found in trying to increase absolute horsepower; the inlet restrictor is very effective and works by simply limiting the amount of air that can be brought into the engine and therefore the absolute power. So engine performance gains are found by improving engine drivability, fuel efficiency, and torque, all the areas low in the rev. range where the inlet restrictor can't effect. This is one of the reasons Audi introduced the FSI engine (direct injection) as it showed gains in drivability and fuel efficiency. While a racing diesel engine does have its challenges and compromises (weight and a premium on intercooling efficiency which potentially effects aerodynamics), the benefits are massive amounts of torque (750+ lb-ft vs. 500) and increased fuel economy. It is predicted that with a similar fuel tank size (to a gasoline powered LMP1 engine), a diesel will be able to run 2-4 laps longer at Le Mans. So the performance gains are worth any engineering headaches.
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Originally Posted by Cadillac Imaj
