Here’s a very interesting article about the new V6 diesel engine of the Audi R18 TDI.
For starters, the engine block is made of aluminum – still a rarity for high-compression diesel engines, even after Mercedes-Benz introduced their design some six years ago. Audi also opened up the angle between the cylinder banks to 120 degrees, giving it a lower center of gravity approaching that of a boxer engine, and relocated the exhaust manifolds from port and starboard to a single unit nestled inside the wide V.
The result is a 3.7-liter turbo-diesel V6 that produces over 540 horsepower. The smaller form factor also allowed Audi Sport to optimize the aerodynamics, while its lower weight allowed the engineers to beef up other components.