The 635 CSi originates from BMW’s 6 series, which are a range of grand-tourers. The first car of this generation was the BMW E24, produced solely in a two-door coupe body style. All of the models used petrol straight-six engines, with the majority using a derivation of the BMW M30 engine family. The E24 was initially based on the E12 5 Series platform, until it changed to the newly-released E28 5 Series platform years later, in 1982.
In November 1984, for the 1985 model year, the North American Market were subjected to a switch from the older 633 CSi, to BMW’s new 635 CSi. This new model uses the M30B34 engine. It is capable of producing 182 horsepower at 4,000 rpm. There was also a luxury version available in North America called the L6, and this featured a leather headliner, trim, and an automatic gearbox.
By 1988, the engine was upgraded to the M30B35. This engine had a capacity of 3.4 litres, and produced 208 horsepower. This was a gigantic leap of twenty-six horsepower from the older 635 CSi’s. The upgrade to the engine resulted in a catalytic converter being equipped to the United States models, and therefore they could offer similar performance to the European models.