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American LeMans
ALMS: Inside the Audi R15
SPEEDtv.com brings you the first impressions on Audi's new technical masterpiece, the R15.
Marshall Pruett  |  Posted March 16, 2009   Sebring, FL
Audi's fresh approach to prototype design on their new R15 is likely to move the bar just as far as its predecessor, the R10 did back in 2006. (Marshall Pruett)
The Audi R15 represents the German marque's unrestricted approach to their second-generation Le Mans Prototype 1 (LMP1). If rival Acura's radical aerodynamics were executed in a smooth, flowing design, Audi's R15 embodies an entirely different philosophy inside and out.

Where the ARX-02a rarely attempts to alter or disturb the flow path of air as it rushes over the car, the R15 channels, forces, and captures air at every opportunity in a bid to produce impressive speeds on the straights and in the corners.

Audi has gone so far as to build a wing-like aperture into the front of the chassis (the openings in the middle of the nose) to gain front downforce, and also move air around the sidepods to intakes just ahead of the rear wheels that channel air into and through the Coke Bottle' rear treatment Audi has given the R15.

Much of the car is an exercise of adapting F1 aero principles to a prototype, and from it's initial laps at Sebring, the R15 has the potential to do what the R10 did in 2006 by resetting the standard for which prototypes are designed.

Misc notes and observations (all refer directly to a photo of some sort in our Audi R15 photo gallery):

The suspension of the R15, at first glance, appears to be constructed from carbon fiber, ala an F1 car, with long tapered farings forming the top and bottom surfaces of the a-arms to maximize aerodynamic gain. But upon closer inspection, the R15 uses conventional steel a-arms and pushrods that have mounting tabs affixed for the carbon farings to be secured with. The 'Senior' R15 ran with farings all day, while the 'Junior Team' ran without them.

Packaging was clearly Audi's main priority with the lighter, better balanced car. The steering rack, third damper, sway bar torsion unit, and a number of other systems and electronics are confined to a horribly small space at the base of the chassis. Getting these items low in the car helps from a PMI standpoint, but as I watched one mechanic struggle to fit his forearm into the small opening to access an item at the front of the chassis, the diameter of his (normal size) forearm filled the access hole, blocking any hope he had of seeing what he was trying to put his hands on.
Losing the extra length of two cylinders, moving the shocks and exhaust pipes forward, and creating a clear channel for air to pass through between the wheels and gearbox is a major improvement for the R15. (Marshall Pruett)

On a similar thread, it could be a function of the newness of the car and the related spares, but the R15's nose took considerable time and became a multi-person effort to install. Their bodywork is usually fitted and made easy to install or remove; I fear that if a nose change is required in the race, the team could do something wholly uncharacteristic -- lose a lot of time in the pits.

The pushrod and rocker system at the front is reasonably straightforward. changing torsion bars is an uncomplicated affair, but beyond that, and as I mentioned above, getting to the 3rd damper, accessing the sway bar lever arms, or manipulating their drop links is the work of midgets.

The underwing on the nose is impressive in its size and surface area. With both Audi and Acura going to a ‘Zero Keel’ design with their new cars, an incredible amount of space has been created beneath the nose and chassis that was previously unavailable to exploit. With the monocoque raised high off the ground and the clear channel between the false floor and the chassis, Audi has extended their underwing further back and at a more steep angle than seen with the R10. That all adds up to serious levels of downforce to work with when needed. I’d have to believe the front ride height is far more critical to maintain than with the R10, and at the right level, can either generate or shed copious amount of downforce. It looks like a strong tool for Audi to manipulate.

With the high exhausts, the force of the exhaust pulses upon start-up and launch are indeed impressive. Compared to the Peugeot, Acura and the Porsche RS Spyder whose exhausts exit outwards, in front of the rear wheels, the R15 blasts a wave of diesel-scented exhaust that will ruffle your clothes. Add in the tail that's curved upwards and the Gurneys at the end of the tail, and that exhaust also propels upwards, right into your face. I can only compare it to the sensation of opening a furnace door and feeling the startling wave of heat and force that can be overwhelming.

Audi's V10 sounds different, but not that much different. Unless you're up close, I doubt you'd catch the absence of two extra cylinders from the exhaust note.

My initial trap speed data taken one car length past start/finish had the R15 2.6mph faster than Peugeot's best, and a telling 6mph over Acura's best. On a 'power' circuit like Sebring, Acura will have their work cut out for them come Saturday. Full radar speeds and analysis to come on Tuesday.

The standard bearer for speed through turn one last year was Peugeot, whose 908s navigated the corner like a movie played at 1.5X speed, but the Lion has been joined, if not surpassed by the R15 in 2009. There's little choose between the two marques for maximum performance in turn one, but it's worth noting that the 908 is entering its third season of competition and barring the 2009 aero regulation changes, has a fully sorted and well balanced car. It's safe to say Audi has barely scratched the surface of the R15's cornering potential.
Audi has used two different front louver treatments in testing so far. (Marshall Pruett)

Both the 908 and the R15 appeared to suffer mild loading and recoiling on the right rear tire while navigating turn one, which likely points to the need for stiffer sidewalls on Michelin's 2009 LMP1 tire. After making tires for the diesels that offered stiff sidewalls to cope with the extra weight they carried across the rear axle, it's possible that with both Audi and Acura fielding P1 cars with less rearwards weight bias in 2009, the first iteration of the P1 rears compensated for lighter use and less stiff sidewalls. I'd expect a new solution in place for testing well before Le Mans.

The R10 was a car without solutions to free internal airflow through the radiators and out behind the vehicle. Shutters on the outside of the sidepods evacuated some of the air, but much of it was forced to fight its way past the V12's air intakes, exhaust and brake ducting. Simply put, there was a party going on at the back of the R10, and it was jam packed with people. The R15 couldn't be more different in this aspect. By moving the V10’s turbo air intake and piping ahead of the engine, and pulling the exhausts back and up (which accounts for the biggest reduction in blockage), Audi has re-imagined how internal airflow with a big diesel engine can be successfully achieved. The R10 cut a wide hole through the air at the rear because of the full width nature of their internal and external airflow. By removing the blockage between the drivetrain and rear wheels, Audi can now pull air in through the tightly-waisted rear, narrow their wake, and leave a smaller, less draggy hole behind the car. Very smart and elegant solution for what is still a large vehicle.

Packaging of the rear suspension has seen the torsion bars moved forward, bring the weight of the related components closer to the center of the chassis. Overall, the rear suspension and gearbox appear to me significantly lower in the car than its predecessor. That lower weight and forward-biased weight is the tonic they needed after dealing with the unruly weight and handling characteristics the V12 delivered. The same style of Ohlins 3rd damper is employed at the rear, just as it was seen on the R10.

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