| Manufacturer | BMW |
|---|---|
| Production | 1989–1996 |
| Predecessor | BMW M40 |
| Successor | BMW M44 |
| Configuration | DOHC Straight-4 |
| Displacement | 1.8 L (1796 cc/109 in³) |
The BMW M42 is a DOHC 16-valve I4 piston engine first built for the E30 318is and 318i 1991 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. The USA version of the 1991 318i only came with the M42 engine.
Profile gaskets on M42s 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, a two stage intake manifold 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 which gives more usable power than the M10s, utilizing a more modern cylinder head and EFI, also distributor-less ignition and later knock sensors.
Applications:
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 (224 kW) | 308 hp (230 kW) | 315 hp (235 kW) |
In the last evolution step the engine puts out an amazing 158 hp/L. Compared to a modern racing engine it was a big achievement.