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PredecessorBMW M40
SuccessorBMW M44
ClassDOHC Straight-4
Engine(s)1.8 L (1796 cc/109 in³)
RelatedBMW M12
ManualsService Manual

The BMW M42 is a DOHC 16-valve I4 piston engine first built for the E30 318is 1989 year model. The engine block is based on the BMW M40, used on the 318i, but had distinctive features such as double overhead cams driven by a timing chain, hydraulic valve lifters, and an increased 10:1 compression ratio.

Profile gaskets on M42s built before 1993 are known to fail prematurely.

Engine Displacement Power Torque Redline Year
M42B18 1.8 L (1796 cc/109 in³) 100 kW (136 PS) @ 6000 172 N·m (127 ft·lbf) @ 4600 6500 1989
103 kW (140 PS) @ 6000 175 N·m (129 ft·lbf) @ 4500 6300 1992


Displacement for the M42B18 was 1.8 L (1796 cc); cylinder bore was 84 mm; and stroke was 81 mm. E30 318iS, 318i (in the U.S.; European versions of the 318i were fitted with the M40 engine), and early E36 318iS/318ti (prior to 1992) models were fitted with versions producing 100 kW (134 hp) and 172 N·m (127 ft·lbf). Later, change in the overhead cam design helped to achieve 103 kW (138 hp) and 175 N·m (129 ft·lbf) coping with the increased weight of the E36 models. The engine uses Bosch M1.7 fuel injection.

The M42 is a popular engine swap for 2002s and E21s. It is a relatively inexpensive swap, and produces more usable power than the M10s, while still being lighter, plus utilizing modern EFI and direct-ignition and a much improved valvetrain.

Further, the long-stroke forged crankshaft from the M47 motor coupled with an overbore of +2 mm will make for a 2.1 L Stroker M42. The 86 mm pistons from a European 3.0 L S50 will produce a high compression, stroker M42 when coupled with the M47 crank. The addition of a MAF conversion from an M50 engine and properly setup cams, valvetrain, and tuning will yield potent output from the "lowly" M42.



S42B20 BMW Motorsport Engine

A racing version of the M42 Engine, called the S42 is known. It was used in BMW´s 320 4-door touring car, participating in the German racing series called STW (Super Tourenwagen Cup). It differed by having individual throttle bodies (ITB) for each cylinder and its capacity was enlarged to 1999 cc. It had eight fuel injectors instead of the standard four. Valve cover and airbox were entirely made of carbon fiber. Lubrication was provided by a dry sump system. Compression ratio was increased and a lightweight head was installed.

Horsepower evolution steps of the S42 Engine:

Year 1995 1996 1997
300 hp 308 hp 315 hp

In the last evolution step the engine puts out an amazing 158hp/ltr. Compared to a modern racing engine it was a big achievement.

See also

External links