The BMW 633CSi was introduced at the same time as the BMW 630CS, but used an injection system instead of the carburettor to prepare the mixture. The L-Jetronic from Bosch was used, which was one of the most modern injection systems in the automotive sector at that time. In September 1979, the engine was modernized using digital motor electronics (DME), which further reduced both pollutant emissions and consumption - but reduced engine performance from 200 hp to 197 hp. The Motronic from Bosch was used, which for the first time controlled ignition and injection based on stored characteristics maps.