"As a point of reference, to show how potent that car is, it ran a 12.4 at 113 mph in the quarter mile with race fuel this past weekend." All-wheel-drive burnouts are entirely possible, which lensman Bidrawn's photos document.
"Les was quite smitten with those," Todd laughed, "and the guy who owns the car was quite eager to demonstrate them. We just rebuilt the tranny for that guy. The transmission in those cars does have some first- and second-gear slider issues. We did the rebuild, and he was out there thrashing on it!"
The black car has a few RS4 parts, like the turbos and inlet tubes, but the exhaust headers are designed by AWE. The factory manifold is a log-type design with each cylinder port dumping into a main tube, whereas the AWE part is a tubular configuration with a collector and an anti-reversion bulkhead design. "We were able to put a tubular header on each side, which some people said could not be done. The factory actually uses a double-walled fabricated tubular design, which some people don't like, because if it isn't done properly, it may crack in time. Our chief of engineering, Kenny McNeil, has been doing this for 20 years and knows how to make a header that doesn't crack. But with our header design a double wall won't fit, so we worked with Swain Tech to come up with a special coating to keep heat out of the engine bay," explained Todd.
The additional airflow from the RSKO4 kit requires more fuel for the engine. Todd elaborated, "New injectors are used, but the size is classified. A number of our competitors have had trouble selecting injectors for their K04 kits, since there are not many choices for this high a horsepower level and the high resistance the ECU requires. The RS4 injectors are Bosch EVC-12 type, which are made for oddly shaped intake tracts like the RS4, while the S4 uses the more standard Bosch injector profile. The RS4 injectors also require the addition of a 5-bar fuel pump to deliver the required fueling for this power level. The Bosch injectors we are using match the factory profile and deliver more than enough fueling even on the factory S4's 4-bar fuel pump, which means fewer parts to be changed. We did all our air/fuel monitoring via a MoTeC wide-band O2 sensor meter." This is mounted in AWE's high-flow sensor housing.
Ignition on the production kit remains stock, even down to the spark plugs. The Silver Bullet's Ignition Solutions coils seem to be working well, as AWE experienced some misfires at 22 to 23 psi, which the coils appear to have fixed.
Todd's performance philosophy at AWE is straightforward: "We don't just make a part with a performance goal in mind; we also beat on it with real-world testing. We beat the crap out of them-we go to track events all of the time. A bunch of us instruct in clubs, so the black car has seen a lot of track time. This proves to us that what we came up with is also very reliable. We've had the motor out of that car so we could evaluate everything, and with 418 bhp it has daily-driver reliability."
As a testament to the intrinsic sturdiness of the Audi design, the aforementioned reliability is achieved with no internal engine modifications. Blocks, cranks, rods, pistons and heads are all unmodified. Todd said, "We knew we could pile on the boost the way we wanted without any problems. It's a tank of a motor. To get any more power out of the Silver Bullet, I think we'd have to get inside the motor, because we are making as much power as we can just by re-engineering everything around it. The stock ports have become a restriction. As far as reliability is concerned, nothing is breaking inside the engine."
Nothing is breaking in the driveline either, which also shows the inherent strengths of Audi design in that area. There is a huge built-in safety factor in the transmission and halfshafts, and Todd believes the upper limit is much higher than the power being produced in even the Silver Bullet configuration.