At that point, Pat decided, like many Manhattanites, that car ownership in NYC was not all that practical. Being a track day enthusiast, Pat decided to immediately rebuild the car, not back to stock trim but as a deadly weapon of a track day car. The S4 was shipped to Bakersfield, California, where Tony Stacey of S&S fabrication built an 8-point rollcage to stiffen the chassis. What's cool is that the cage is integrated into the interior somewhat unobtrusively while still providing good protection to the driver. S&S also fabricated a custom center console to house auxiliary switches and an aluminum foot box to properly position the driver's feet. For safety, the stock seats were replaced with Sparco Corsas, and G-Force 5-point harnesses hold the driver tight. An A.S.P.A on-board fire system stands ready, just in case, while Pat relies on Bell, Sparco, Downing and G-Force for personal safety equipment. S&S also custom fabricated dual 3-inch downpipes, which feed into a single 3.5-inch stainless exhaust, with an easily removable for-track-events bullet muffler.
Next stop for the S4 was for an engine makeover at AMS. AMS is one of the premier tuners of VW and Audi products, and has plenty of real race experience. Marc Kalaydjian of AMS stuck with tried and proven OEM Audi parts for the buildup of Pat's monster motor, not a bad idea considering that OEM parts are usually better-engineered with better quality than many aftermarket performance parts.
Pumping out an impressive and road race reliable 445-wheel hp and 410 lb-ft of torque at 1.3 bar of boost, the 2.7 liter, 9.3:1 compression V6 engine is amazingly stock. Audi engines are known to be quite robust and Pat's car proves the point by not suffering a single engine problem throughout the 2005 season, a mute testament to the strength of the engine and AMS's tuning skills. The major power increasing modification on the car is the use of AMS-upgraded turbos, which replace the stock KO3 units with a hybrid of various OEM KKK parts. A compressor section from the euro-market only, limited edition RS6 was used, as was a larger turbine section from the KO4 turbo used on European 1.8-liter motors.
The European-market, limited edition 380-hp RS4 was also used as the source for many of the other upgrades on the motor. A free-flowing RS4 airbox leads to a bigger RS4 throttle body, feeding less restrictive RS4 inlet tract ducting. Larger, more efficient and less restrictive dual RS4 side-mount intercoolers further uncork the intake tract while densifying the intake charge.
An RS4 intake cam moves the valves more aggressively and AMS did a mild port job on the cylinder heads. A larger, ported RS4 intake manifold was fitted to the S4 heads using AMS adaptor plates. The manifold is topped off with larger RS4 injectors. AMS then reflashed the ECU, modifying the fuel and spark maps for more boost and larger injectors. Other than these straightforward mods, the rest of the engine is completely stock.
Since AWD cars are notoriously hard on their drivetrains, the 445 horses are fed through a Sachs Race Engineering 6-puck metallic clutch disc and pressure plate, bolted to a lightweight, custom machined AMS flywheel.
Stasis Engineering modified the transmission, performing their heavy-duty rebuild and installing stronger shift forks. A Stasis Engineering center differential with a 4:1 bias torque split was used, as opposed to the stock 2:1 split. This allows the center diff to transfer more torque to the wheels with the most traction, reducing front wheel spin under power, a common S4 problem.