A moment before Ullrich’s answer Tom Kristensen had driven the R10 under the Eiffel-tower into the lawn of the Natural History Museum of Paris.  It was very fitting environment. It paired the names of Eiffel and Porsche (The Porsche family owns 20 % of VW/Audi, and Ferdinand Piech is a grandson of Ferdinand Porsche sr.).  Furthermore the R10 launch took place on the home ground of Peugeot.  There is also a historical note.  The Porsche family felt extremely bitter towards the Peugeot family after the II WW. The totally apolitical Reichsingenieur Dr. Porsche and Dr. Anton Piech, father of Ferdinand, were then jailed for almost two years and the family blamed Pierre Peugeot.  Porsche sr. never regained his health afterwards. Quite an interesting story really. It's the winners who write the history.

Back to R10. The sound of the engine was quite silent. The note was not too continuous supporting the theory of a relatively low combustion ratio. Tom parked it, apparently tried to get it in reverse, but only the noise of grinding teeth was heard. The gearbox was obviously not quite tuned yet.

Visually the car was not a surprise.  Ever since the first rumors of the engine being a 12-cylinder there had been speculation of a longer wheelbase.  And longer it was.  Scaling from the photos it would appear to be pretty close to 3000 mm.  Also, Audi claims that the wheelbase is comparable to that of the new Q7 model (3002 mm).  It's not only the long engine but also that the driver position is shallower and that additionally contributes to the wheelbase. Audi says that the R10 is a "50 mm flatter" design than the R8.

You could see the new LM-regulations being applied.  The front underbody had a raised center section, the longitudinal underbody edges had a high ride height due to the compulsory seven-degree slant (chamfer).  At the back the compulsory geometry behind the wheels (maximum rear overhang of 750 mm, rear side plates) disturbs the natural lines to some extent.  On the top side you can see the double roll over bars.  Anything else?  The Bentley has inspired the front-end aerodynamics, air being directed between the suspension wishbones.

The R8 was built with a load carrying monocoque.  The other body panels were then bolted to this monocoque unstressed.  On the R10 a significant amount of body panels have been integrated to the monocoque to give higher stiffness to weight ratio.  It's the Barnard thumb rule: every possible bit has to have at least two functions.

LMP tend to have inherent understeer.  Therefore Audi has opted for a bigger than standard front wheels.  The R8 had 33 cm wide and 65 cm diameter front wheels and the new R10 has the same width but 68 cm diameter.  The logic seems to go: more torque, more traction and more understeer.  It's a bit contradictive as the more longitudinal tractive force you apply the more lateral friction will be lost (friction circle).

Really the most interesting part is not the exterior.  It is the engine.  Having followed motor sport for over thirty years, frankly the R10 engine is probably the most important release in motor sport during my lifetime.  This development is on par with the Cosworth Process molding technique and the Lotus Engineering-developed active suspension. 

Why?  This engine is a window to the present diesel-technology.  It's a well-known fact that a diesel engine is more efficient fuel burner than an Otto-cycle engine (gasoline engine).  Furthermore in the last few years developments in the Common rail technique, diesel fuels and soot filters/catalysators have made diesels emissions-wise a comparable choice to the gasoline engines –in Europe that is.  In the US diesel technology is still in its infancy.  To my knowledge the best diesel engines are not even sold in the US because of the low quality of the diesel fuel – perhaps with the exception of California.  In this sense the message of the R10-project has a huge significance.  There is more potential left in diesel-technology than in Otto-technology. It feels good that racing is used for more than futile entertainment.

The modern direct-injection common rail turbocharged diesels have not only the power of their Otto-brothers, but a lot more torque.  To give you an idea compare, the two Audi A6 engines below.  Draw your own conclusions.
 
 

Now, there isn't really anything radical in the Audi R10-engine, but it is done with the most modern existing diesel-technology.  It utilizes the third generation Bosch piezo-actuated injectors capable of handling 2000 bar injection pressure, an aluminum crank case (MB has an aluminum diesel in production), catalytic soot filters, and variable-geometry turbine vanes.  It utilizes partly synthetic GTL-diesel fuel (Gas-To-Liquids) with setane number close to 70.  This means a short ignition lag, which in turn means fast burning and the possibility to control maximum cylinder pressure with a clever injection.  Traditionally the Achilles heel of the tuned turbo diesels has been the head bolts which have yielded under the maximum cylinder pressures.  With a high setane number one can make the maximum cylinder pressure peak wider and lower.

The operational rev band of the R10 is an impressive 3000–5000 rpm.  Tom Kristensen, "The best band is 3000–5000 and you can go even a bit over."  Tom continued to say that the band is quite narrow, but if you think about it, it is actually 40 % of the total band, which is much, much more than in many race engines.  He is probably used to the very driveable FSI-engine.  The race tuned turbo diesels usually have a relatively low compression ratio and a high boost.  This easily produces an engine which is not as driveable at part load.  Tom may have noticed this and interprets it as a narrow band.  It may be a tricky band but not a narrow one.

It appears that the restrictor does not limit the engine power.  With a stochiometric ratio the engine could produce about 800 ps. Yes, of course, diesels require air excess.  However, the maximum allowed boost seems to be the real limiter.  Audi tells that the top power of the R10 is about 650 hp.  To get this power at about 5000 rpm and 2940 mbars requires a very high volumetric ratio i.e. excellent cylinder fill.  In practice, the R10 must have a very efficient intercooling system to get the required air mass into the cylinder.

The maximum torque is above 1100 Nm (810 lb-ft).  The R8 generated about 700 Nm (520 lb-ft).  If the R10 works as turbo-diesels tend to, the maximum torque is constant 3000–4000 rpm, above which there is almost a constant power band (diminishing torque).  The Audi engineers have calculated that the R10 could do one ore lap with a tank full at the Le Mans Sarthe track.  This would mean that the R10 is about 5 % more efficient fuel burner than the R8 FSI over the track.  The Sarthe is about 80 % WOT (Wide Open Throttle) so the difference is not that enormous.  At tracks with a higher part load percentage (Sebring, Road Atlanta) the difference is going to be bigger.

Interestingly Tom also stated, "Beyond the second gear you can't hear the engine noise under the wind and it makes driving a bit difficult.  We, drivers, need to adjust and adapt our styles to the engine."

The Ricardo-Judd diesel shows even more impressive figures than the R10, but those figures are frankly too impressive.  I am pretty certain that the 6000-rpm of the Ricardo is achieved with a very poor efficiency.  Probably more noise and high exhaust temperatures than power.  I am not quite sure how to deal with the Ricardo figures.  I mean 6000 rpm – with a diesel that has characteristically slow burning fuel?

Audi decided to fit soot filters to the engine.  They'll definitely eat some power but ultimately the green message is more important.  The type of the soot filters is not specified though, but it'll probably be an extra 15 kg to carry.

There are still some interesting figures about the R10 engine that have not been published.  They haven't stated the compression ratio or the weight of the engine.  My guesstimate is that the compression ratio is 15:1–17:1 and the weight of the engine is somewhere at 250 kg.  The Ricardo-diesel is said to weigh less than 180 kg.  It simply sounds too good to be true – or at least too vulnerable.  It would not be such a surprise to find out that the R10 would be somewhat overweight.

The huge torque has required a new gearbox.  Again the gearbox has a pneumatically driven drum selector (common in motorbikes).  Interestingly the manufacturer is different to that of the old gearbox.  The R8-gearbox was a Ricardo design where as the R10 is by X-trac.  Given the reliability the Ricardo box has shown, the move to X-trac is quite surprising.  Never mind,  X-trac has a reputation of reliable goods too. 

It is pretty likely that the R10 will win in the Le Mans 2006 given the reliability is there.  Why wouldn't it be?  Time will tell.  Obviously there are a number of unknown issues in every new racing engine let alone in a diesel-racing engine.  In the 2007 Le Mans Audi will face Peugeot with a diesel.  Remember that Peugeot was humiliated in F1, then won in the WRC and then failed in the WRC. There is a lot to prove for them.  In any case, the winner will write history.