The Audi S4 is, to many, the ultimate expression of a refined European sport sedan. It has all-wheel-drive traction and combines the benefits of turbocharging with displacement. The S4 is also luxurious, with stellar execution of world-leading interior and exterior design. It is a beautiful car, capturing much of what european car strives to be about. Shaking down a bunch of S4s on a dyno, dragstrip and road course was a natural follow-on to our 1.8T Challenge.
This S4 Shootout followed a format similar to the 1.8T Challenge, but with improvements. Kevin Schrantz, driver of the Hagestad Racing Volkswagen Jetta in SPEED World Challenge, again made his services available for the road course and dragstrip. Having fewer cars made it possible for the magazine staff to gather all the performance data, and we added braking distance. Using GIAC's four-wheel Mustang made it possible to dyno all the cars in one day. We used a better method of calculating scores that is more linear and separates performances more meaningfully.
We initially planned on six or seven entries, but as the event drew near, we found ourselves unable to say no to 12. The cars from Achtuning, AWE and Chris Clark should be familiar to regular readers of european car, as they have previously been featured within its pages. Several well-known and respected enthusiasts joined the group. The rest of the cars were from tuning companies we've seen good things from in the past.
Dyno
Garrett Lim shut down GIAC and opened the facility to european car, generously providing the use of his dyno and his staff's time. GIAC's Mustang four-wheel chassis dyno uses a combination of inertia (inescapable due to the mass of the rollers) and electrical resistance loading. The time required for a pass and the resistance offered by the dyno are determined by Mustang's software, partly using factors entered by the operator. We entered the numbers used by GIAC for all S4s and left them alone. Torque output reacted by the electrical load units is measured with load cells on lever arms. Garrett reports that, after calibration by a Mustang engineer, GIAC's dyno in two-wheel mode yields results very close to a Dynojet 248's numbers. Unlike most four-wheel dynos, the Mustang's front and rear rollers are mechanically linked, so they always turn the same speed. There would be no problem managing front-to-rear torque split.