ALMS 2006
Audi R10 TDI #2 (Audi Sport North America), Dindo Capello and Allan McNish

IMSA has published a bulletin that affects the refuelling rig restrictor of diesel cars participating in the American Le Mans Series, specifically the Audi R10 TDI cars. The change limits the refuelling restrictor from the current 38mm permitted under the regulations to 33mm, with immediate effect.

Dr Wolfgang Ullrich, Head of Audi Motorsport:
“Of course we are not happy about changing the rules in the middle of the season after all the hard work we have done based on the original rules. The adjustment means that our refuelling stops will take several seconds longer because diesel has a higher viscosity and thus a lower flow speed. Originally, a larger diameter had been allowed for diesel engines to make sure that diesel and gasoline engines can be refuelled in the same amount of time.

“Audi accepts the change because it serves to ensure that during a refuelling stop both types of engines receive the same amount of energy within the same period of time. It is common knowledge that a litre of diesel fuel has a higher energy content than a litre of gasoline mainly because of its higher density. ACO and IMSA want to ensure that in future a full tank of every type of fuel used by different engine concepts contains the same amount of energy. This is not an easy task for the 2007 rules because there are many ways to analyse the different fuel components. For example, the influence on oxygen that is included in racing fuel but not in diesel is crucial.

“Changing the fuel tank capacity is a type of intervention which cannot be implemented in a short time for technical reasons. Thus IMSA has chosen to reduce the diameter of the diesel fuel rig for the rest of the season to ensure that both types of engines get the same amount of energy during refuelling in a given time. The issue of ‘energy content’, in our opinion, should be settled as a result of these measures for the 2006 season in the American Le Mans Series.”