Unique TDI engine for the Audi R18 TDI
• Only six weeks to go before the 24 Hours of Le Mans
• Compact V6 TDI power unit with single turbocharger
• Exhaust manifold and VTG sit between cylinder banks
Ingolstadt, April 28, 2011 – The new Audi R18 TDI with which Audi targets its
tenth victory in the famous 24 Hours of Le Mans on June 11/12 is ready today
with “tomorrow’s” technology. During development of the new LMP1 sports car
the integration and future electrification of the powertrain and various possible
concepts for energy recuperation have been taken into account.
“We are very conscious of such systems,” explains Head of Audi Motorsport Dr.
Wolfgang Ullrich. “In our opinion, just as soon as this technology proves to be the
most efficient we will use it at Le Mans.”
Although diesel engines have been repeatedly restricted by the regulations since
their victorious introduction in 2006, Audi relies on TDI power once again for its new
LMP1. “Audi invented the TDI engine and is convinced that this technology remains
one of the most efficient and modern forms to power a car – especially at Le Mans
where engines with high specific power, low fuel consumption and low emissions are
a necessity.”
New regulations devised by the Automobile Club de L’Ouest (ACO) and introduced
this year dictate significantly smaller engines. Audi has chosen a particularly
compact 3.7 liter V6 TDI engine, which is about 25 per cent lighter than the V10 TDI
power plant previously fitted to the older R15 TDI, and which leaves all options open
for the technicians with regard to electrification and energy recuperation. “This
would not be the case with a V8, for example, which is also permitted by the
regulations,” explains Ulrich Baretzky, Head of Engine Development at Audi Sport.
However, Audi does not only surprise with its extremely compact engine. The
concept is also innovative for an LMP1 sports car. To lower the center of gravity as
much as possible and to improve airflow through the car, the exhaust manifold
were migrated from the left and right hand sides of the engine to sit between the
two cylinder banks. “Hot side inside” is the name given to this concept by specialists,
which was implemented in similar form in Formula 1 in the 1980s. But the V6 TDI
engine powering the Audi R18 TDI, which has a cylinder angle of 120 degrees and
thus an extremely low center of gravity, is technically generations further along the
line and is also a technology-demonstrator for future production engines.
In contrast to previous Audi Le Mans sports cars, which all had twin turbochargers,
the R18 TDI is quite logically now only fitted with a single turbocharger that also
sits above the engine and draws its air directly through the air scoop mounted on
the roof. “In this way we are able to convert the dynamic pressure generated at high
speeds with minimal losses into power,” explains Dr. Martin Mühlmeier, Head of
Technology at Audi Sport.
The mono-turbo concept developed in cooperation with Garrett was only made
possible by the variable turbine geometry (VTG) already used victoriously in the R15
TDI. “Otherwise the response characteristics of such a large turbocharger would just
be too bad,” explains Baretzky.
The concept was continued logically through a single pipe exhaust that exits at the
rear of the R18 TDI below the new fin which is stipulated by the regulations. “This
also stands for Audi ultra lightweight technology,” says Baretzky, “since we save
components and weight – for example for a second diesel particle filter.”
Audi Sport has worked since July 2009 on the innovative engine concept for which
numerous new routes had to be explored. To control the enormous ignition
pressures and loads now only distributed between six cylinders, a unique method of
cooling the cylinder heads was developed for the aluminum power unit, a concept
that could also be interesting in the future for production.
Owing to the compact engine and uncluttered flanks, the airflow from the coolers
can now exit practically unobstructed through the rear end. “We could increase the
aerodynamic efficiency of the car as a result,” says Martin Mühlmeier, Head of
Technology at Audi Sport. This aspect is even more important than ever before at Le
Mans due to the reduction in engine power – for the Audi R18 TDI more than 397 kW
(540 hp).
Another unique aspect of the new Le Mans sports car is its unusual sound. The Audi
R18 TDI is probably the quietest race car Audi Sport has ever built. “Noise is unused
energy,” stresses Dr. Wolfgang Ullrich who is delighted by the whispering murmur
of the R18 TDI. “The sound is unique,” raves Le Mans record winner Tom Kristensen.
“It’s hard to describe. You have to hear it yourself. I think it’s fantastic.”
Audi Communications Motorsport/for Acreditated and Autorized Media Press.
