TECHNOLOGY - ENGINES
The architecture of a diesel
Audi Sport’s head of engine technology, Ulrich Baretzky, explains the thinking behind the company’s all-conquering powerplants
I
t was said to be the engine Ulrich Baretzky had wanted to build for years, and once the V12 diesel engine fitted to the Audi R10 TDI had
proven itself he was given the green light to progress with his concept for the new R15 chassis. The story starts after the decision was taken to replace the R10 TDI with an all-new Le Mans Prototype, with an all-new engine. ‘Choosing an engine
configuration was not an instant decision, as we weighed up the differences between eight, 10 and 12-cylinder layouts,
taking the following factors into consideration: vehicle packaging; displacement; engine weight; c of g position; overall length; specific piston loads; vibration behaviour; development potential and transfer from / to production car engines,’ says Baretzky. Computer simulation of the
complete car on the Le Mans track produced a clear set of design requirements for the new powerplant: the power would have to exceed 650ps (641bhp),
with more than 1100Nm of torque in a wide, usable rev range and to be able to use a five- speed gearbox. It could also not weigh more than 220kg and it had to be fully stressed. ‘Many of the targets for the
new engine resulted from the demands to reduce the engine’s overall length, and to be able to change the car’s weight distribution as a consequence. The overall dimensions for
The V10 TDI unit produced more than 600bhp and had a maximum torque of over 1050Nm. It was 100mm shorter than the V12 used in the R10, on the request of Audi’s chassis department who, Baretzky says, were much more involved with the early development of the R15 than they were on the R10. ‘In the past [read: with the R10], the engine came first and they built a car around it. With the R15 we showed the chassis team pretty early on what we wanted to do, and they asked us to make a shorter, lighter engine. So we removed two cylinders.’
Le Mans •
www.racecar-engineering.com
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