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Written by:
Marshall Pruett
08/07/2008 - 11:55 PM
Elkhart Lake, WI
Audi's refuelers could be staring at the refueling port for as much as five extra seconds at each pit stop thanks to bulletin '08-05.' (Photo: Marshall Pruett) » More Photos
Audi’s Syrupy Strategy
Keen observers of the www.ImsaRacing.net website spotted tech bulletin IMSA BULLETIN # ALMS 08-05 posted on July 7th, 2008, and it could have a major impact on the LMP1 vs LMP2 battles we've enjoyed since 2007. This simple two clause bulletin has the potential to massively alter the outcome of
the remaining ALMS races, starting this weekend at Road America.
1) In accordance with Attachment 2, Para 10 of the American Le Mans Series SSR, the following adjustments are to be made:
a. The maximum height of the autonomous fuel rig for diesel powered cars is hereby lowered to the standard maximum height of 2.00m above the surface where the refueling takes place.
b. The maximum capacity for LMP Diesel cars in the American Le Mans Series (only) shall be a maximum of 85 liters on board.
2) These changes take effect 21days following publication.
“I can’t say how long our predictions say this change will add to our pit stops, but it could be a game changer. Porsche and Acura probably smiled when they heard about this rule change,” Audi’s Brad Kettler said. “Any extra time we’ll end up sitting at a standstill helps our competition. It’d be the same for anyone.”
The changes listed call for two adjustments—lowering the height of Audi’s refueling tank from 2.5 meters to 2.0 meters off of the ground. If half a meter difference in tank height sounds trivial, think about the loss of half a meter’s gravity to force the syrupy diesel fuel into the R10’s fuel cell.
“Diesel flows so much slower than regular gasoline like everybody else uses. It’s common physics: the higher the pit lane tank is off the ground, the harder that gravity pushes down on the diesel fuel to fill the car. The lower they make us mount the tank, the slower the diesel goes in during a stop.”
Audi has also been granted an extra 4 liters of fuel starting this weekend. It’s another change that could penalize the team. “Some extra diesel in the car could be helpful, but it also makes us sit on pit lane waiting for that extra fuel to go into the car. This should
The R10 made its debut in 2006 utilizing a 90L fuel cell, but as their cars proved capable of running for ridiculously long between pit stops, the ALMS quickly reduced their cell capacity to 81L. With less fuel on board, the Audi’s would need to stop in the same general timeframe the P2 cars could last on a tank of gasoline. Fuel flow restrictors were also placed in the team’s refueling hoses to slow the speed in which it took to fill the tank.
Lowering Audi's refueling tank by .5M, or 1.5ft, doesn't seem like it would have a huge impact on how long it takes to fill the R10's tank, but with syrupy diesel fuel, it certainly won't make it flow any faster. (Photo: Marshall Pruett) » More Photos
Construction of a new fuel cell for the R10 has been another challenge for the team. “As a company, Audi always looks to create an optimal design for every task, so when IMSA announced we’d be moving to a bigger capacity, Audi Sport in Germany started immediately on a new 85L design. Then they built a prototype, tested it on the bench and in a car in the factory, validated the tank volume and all of the pumps and systems that make it work, and finally, they track tested the new tank. A fuel cell isn’t like a balloon you just inflate a little bit more to fit a little bit more. It was a redesign of the complete system from top to bottom.”
It’s also interesting to learn how Audi chose to fill a void in the car that was built to house a fuel cell 90L in size. “The aperture in the R10 was originally created for a 90L cell, and we built carbon fiber plates to occupy the unused space in the hole where the 81L cell used to sit. We’ve also had to design and built new plates—ones that are a little bit smaller—to work with the 85L tank.”
All of the work to create a new cell will buy Audi some freedom in how they choose to use the extra 4L of diesel capacity. The rules don’t require them to use all 85L available, so doing timed fills to use an amount less than 85L could be called for depending on the situation.
One thing is for sure—the estimated 3 to 5 seconds of extra time the R10’s could be sitting still as the diesel flows like molasses into their new fuel cells will be agonizing for the team to watch. For their rivals, it’s a change they wish had been implemented much earlier.
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