BMW's M5 series

The M5 was produced in four different versions based on intended export locations. These were the left-hand drive (LHD) Euro spec, the right-hand drive (RHD) UK spec, the LHD North American (NA) spec for the United States and Canada, and the RHD South African (ZA) spec.

The LHD, RHD Euro Spec M5s and the ZA spec M5s had the M88/3 powerplant which delivered 286 PS (210 kW; 282 hp) whereas the North American 1988 M5 was equipped with a variant of the M88/3 called the S38 B35 which was equipped with a catalytic converter, which, combined with slightly lower compression of 9.8:1 versus 10.5:1 for the M88/3 reduced the power output to 256 hp (191 kW; 260 PS). The S38 also differed from the M88/3 in that it had a dual-row timing chain as compared to the M88/3's single row timing chain. The S38 B35 was used in the NA-Spec E28 M5 and E24 M6. Late production catalyst equipped versions (117 examples) of the European M635CSi were also equipped with the S38 B35. Initially 500 were to be made for the US Market, BMW later increased production to as many as 1,370 units for the US and Canadian markets, although the generally accepted figure is 1,244 units sold.