timing belt tensioner. This marked the first use of four-valves-per-cylinder heads and DOHC in the 944, derived from the 928 S4 featuring a redesigned camshaft drive, a magnesium intake tract/passages, magnesium valve cover, larger capacity oil sump, and revised exhaust system. The alternator capacity was 115 amps. The wheel bearings were also strengthened and the brake servo action was made more powerful. Floating 944 calipers were standard, but the rear wheel brake circuit pressure regulator from the 944 turbo was used. Small '16 Ventiler' script badges were added on the sides in front of the body protection mouldings. Performance figures included 0- being achieved in 6.5 seconds (Best) and a top speed due to a curb weight. It also featured an improved programmed Bosch Digital Motronic 2.1 Computer/DME with dual knock sensors for improved fuel performance for the higher 10.9:1 compression ratio cylinder head. Like the 944 Turbo, the 944 S received progressive springs for improved handling, larger front and rear anti-roll bars, revised transmission and gearing to better suit the 2.5 L DOHC engine's higher 6,800 rpm rev limit. Dual air bags, limited-slip differential, and an anti-lock braking system were optional on the 944 S. A Club Sport touring package (M637) was available as was the lightweight 16-inch CS/Sport Fuchs 16x7 and 16x9 forged alloy wheels. This version was raced in Canada, Europe and in the IMSA Firehawk Cup Series held in the U.S. Production was only during 1987 and 1988. It was superseded in 1989 by the 'S2' version. The 1987 944 S' power-to-weight ratio was such that it was able to accelerate from 0 to 100 km/h in 6.5 seconds thus matching the acceleration of its newer larger displacement 3.0 L 944 S2 sibling. 944 S2 In 1989 the 944 S2 was introduced, powered by a naturally aspirated, dual-overhead-cam 16-valve 3.0 L version of the 944 S' engine. With a bore of and a stroke of , it was the largest production 4-cylinder engine of its time. The 944 S2 also received a revised transmission and gearing to better suit the 3.0 L M44/41 powerplant. The 944 S2 had the same rounded nose and a rear valance found on the Turbo model. Quoted performance figures included a 0–97 km/h acceleration time of 6.0 seconds (0–100 km/h being achieved in 6.8 seconds) and a top speed of for the cars with a manual transmission. A Club Sport touring