they would be required to race a front-wheel-drive car, until they managed to persuade IMSA to change the rules, thereby permitting cars to race with something other than their original drivetrain, and therefore with a redesigned chassis. To AAR's delight, IMSA did change the rules, and the car was converted to rear wheel drive. One outstanding feature of the car was the 4T-GTE engine, from its Safari Rally-winning, Group B predecessor, producing around . Piloted by the likes of Chris Cord, Willy T. Ribbs, and Dennis Aase, the car was dominant in its class right up until the team's move to GTP. Utilizing the same engine, it became dominant once again. Other teams would follow this example, with notable cars such as the Chevrolet Beretta (in the Trans-Am series) and the Mazda MX-6 (in IMSA GTU). The Celica was one of just a few cars that had broken away from its production GT derivatives of the earlier years. With a full spaceframe chassis, they became serious race cars. By 1987, the category became dominated by factory teams, with testing sessions becoming common, and rules tailored to welcome them in rather than turn them away. Otherwise, the cars were required to closely resemble their showroom counterparts, though fenders could be widened, increasing the track up to . There were no restrictions on body materials, as most teams favored removable, easy to repair fiberglass (meaning one of the only remaining panels from a car's production counterpart was the steel roof structure). Another car that exploited the rules was the Audi 90. With its advanced Quattro four-wheel-drive system, the car had the potential to dominate during the 1989 season. The car performed well, but faced heavy competitions from two factory teams; the Roush Racing Mercury Cougar XR7, and Clayton Cunningham Racing's Nissan 300ZX, which took seven wins out of fifteen. Audi stayed away from the early season endurance classics (Daytona and Sebring), and had two cars drop out of the race in two different rounds, thereby costing them both the manufacturer's and driver's titles, Hans-Joachim Stuck driving. Another manufacturer to experience a run of wins was Mazda. After some success by the Mazda RX-2 and Mazda RX-3, the Mazda RX-7 won its class in the IMSA 24 Hours of Daytona race an amazing ten years in a row, starting in 1982. It also won eight IMSA GTU championships in a row from 1980