500 SL. At this time, the V8 engines were re-tuned for greater efficiency, lost a few horsepower and consumed less fuel, largely due to substantially higher (numerically lower) axle ratios that went from 3.27:1 to 2.47:1 for the 380 SL and from 2.72:1 to 2.27:1 for the 500 SL. From September 1985 the 280 SL was replaced by a new 300 SL and the 380 SL by a 420 SL; the 500 SL continued and a 560 SL was introduced for certain extra-European markets, notably the USA, Australia and Japan. Also in 1985, the Bosch KE Jetronic was fitted. The KE Jetronic system varied from the earlier, all mechanical system by the introduction of a more modern engine management "computer", which controlled idle speed, fuel rate, and air/fuel mixture. The final car of the 18 years running 107 series was a 500 SL painted Signal red, built on 4 August 1989; it currently resides in the Mercedes-Benz museum in Stuttgart, Germany. North American models North America was the key market for this Personal luxury car, and two thirds of R107 and C107 production was sold there. The R107/C107 for the North American market sported four round low-output sealed beam headlights, due to unique U.S. regulations. Sales in North America began in 1972, and cars wore the badge 350 SL, but actually had a larger 4.5L V8 with 3 speed auto (and were renamed 450 SL for model year 1973); the big V8 became available on other markets with the official introduction of the 450 SL/SLC on non-North American markets in March 1973. US cars sold from 1972 through 1975 used the Bosch D Jetronic fuel injection system, an early electronic engine management system. From 1974, the front and rear bumpers were dramatically lengthened, by on each end, to comply with the U.S. National Highway Traffic Safety Administration regulations, that mandated no damage at an impact of . R107 and C107 cars were exported to the US with low compression 4.5 liter V8 engines to meet stringent US emissions requirements, yet still provide adequate power. US models sold from 1976 through 1979 used the Bosch K Jetronic system, an entirely mechanical fuel injection system. The 450 SL was produced until 1980. Starting in 1980, US cars were equipped with lambda control, which varied the air/fuel mixture based on feedback from an oxygen sensor. The smaller engined 380 SL replaced the 450SL