hatch. From 1987 through 1995, the front spoiler was integrated into the nose and the rear spoiler became a separated wing rather than an integrated piece, and side skirts were added. The rear tail-light configuration was also different from previous models. GTS models had wider rear fenders added to give more room for 9-inch wide wheels. Another easily noticeable visual difference between versions is the style of the wheels. Early 928s had 15-inch or 16-inch "phone dial"-style wheels, while most 1980s 928s had 16-inch slotted "flat disc" wheels, CSs, SEs and 1989 GTs had 16-inch "Club Sport" wheels, later GTs had 16-inch "Design 90" style wheels which were also option on same period S4s (shared with the 944 as well), the GTS used two variations of the 17-inch "CUP" wheels. Later variants Porsche introduced a refreshed 928 S into the European market in the 1980 model year, although it was the summer of 1982 and MY 1983 before the model reached North America. Externally, the S wore new front and rear spoilers and sported wider wheels and tires than the older variant, but the main change for the 928 S was under the hood, where a revised 4.7 L engine was used. European versions debuted with , and were upgraded to for the 1984 model year. From 1984 to 1986, the S model was called S2 in United Kingdom. These cars used Bosch LH-Jetronic fuel injection system and purely electronic Bosch ignition, the same systems used on the later 32-valve cars, though without the pollution controls, the high lift camshafts provided considerably more power than reported. It was not uncommon for these cars to show engine rated power on a chassis dyno. North American-spec 1983 and 1984 S models used among other differences, smaller valves, milder camshafts, smaller diameter intake manifolds, and additional pollution equipment in order to meet emissions regulations, and were limited to as a result. Due to low-grade fuel, the 16-valve low compression S engine was made for the Australian market in the 1985 model year. It had a 9.3:1 compression ratio pistons as opposed to the normal 10.4:1 but used the same large intake, high lift cams, large valves, etc. of other S engines. As the faster European model was not available in the United States and Canada during the first three years of its existence, a "Competition Group" option was created to allow North American