The BMW 524td also provided a diesel model for the market launch of the third BMW 5 Series generation (E34). The six-cylinder inline engine (M21) was taken over from the predecessor model but it was given a smaller turbocharger to improve the responsiveness of the engine. A digital diesel electronic system (Bosch EDC) was also fitted to further optimise the combustion processes. At this time, it was unique and a world first. From 1989, an oxidation catalytic converter was used as standard to improve environmental compatibility. In September 1991, the BMW 524td (E34) was replaced by the BMW 525tds (E34) when a new generation of BMW diesel engines (M51) was launched. More than 70,000 units were produced and it was only supplied as a sedan.