BMW M42B18

M42B18The BMW M40B18 is a 1.8 liters (1,796 cc, 109.6 cu·in) straight-four, four-stroke cycle, natural aspirated gasoline engine from the BMW M42-family. The engine was manufactured from 1989 to 1996.

The M42B18 engine features a cast-iron cylinder block, an aluminum head with a chain-driven double overhead camshafts (DOHC) and two valves per cylinder (16 in total) with hydraulic tappets. Cylinder bore and piston stroke are 84.0 mm (3.31 in) and 81.0 mm (3.19 in), respectively. Compression ratio rating is 10.0:1.

This engine used a Multi Point Fuel Injection system (MPFI), the Bosch Motronic M 1.7 engine management system and coil-on-plug ignition system with fully electronic controlled ignition timing. Later versions of the M42 also feature a dual length intake manifold (“DISA”).

The BMW M42B18 engine produced 136.0 PS (100.0 kW; 134.0 HP) at 6,000 rpm of maximum output power and 172.0 N·m (17.5 kg·m, 126.8 ft·lb) at 4,600 rpm of peak torque for BMW 318i (E30) model (1989-1992 production years), or 140.0 PS (103.0 kW; 138.0 HP) at 6,000 rpm of horsepower and 175.0 N·m (17.8 kg·m, 129.0 ft·lb) at 4,500 rpm of torque for BMW 318i (E36) model (1992-1996).

The breakdown of the engine code is as follows:

  • M42 – Engine Family
  • B – Gasoline
  • 18 – 1.8 Liter displacement

General information

Engine Specifications
Engine codeM42B18
LayoutFour stroke, Inline-4 (Straight-4)
Fuel typeGasoline
Displacement1.8 L, 1,796 cc (109.6 cu in)
Fuel systemMulti Point Fuel Injection (MPFI)
Power adderNone
Max. horsepower E30: 136.0 PS (100.0 kW; 134.0 HP) at 6,000 rpm
E36: 140.0 PS (103.0 kW; 138.0 HP) at 6,000 rpm
Max. torque E30: 172.0 N·m (17.5 kg·m, 126.8 ft·lb) at 4,600 rpm
E36: 175.0 N·m (17.8 kg·m, 129.0 ft·lb) at 4,500 rpm
Firing order1-3-4-2
Dimensions (L x H x W):

Cylinder block

Cylinder block
Cylinder block alloyAluminum
Compression ratio:10.0:1
Cylinder bore:84.0 mm (3.31 in)
Piston stroke:81.0 mm (3.19 in)
Number of piston rings (compression / oil):2 / 1
Number of main bearings:5
Cylinder inner diameter (standard):84.000-84.014 mm (3.3071-3.3076 in)
Piston skirt diameter (standard):83.985 mm (3.3065 in)
Piston ring side clearance:Top0.020-0.200 mm (0.0008-0.0079 in)
Second0.020-0.100 mm (0.0008-0.0039 in)
Oil0.020-0.100 mm (0.0008-0.0039 in)
Piston ring end gap:Top0.200-1.000 mm (0.0079-0.0394 in)
Second0.200-1.000 mm (0.0079-0.0394 in)
Oil0.200-1.000 mm (0.0079-0.0394 in)
Crankshaft journal diameter:60.000 mm (2.3622 in)
Crankpin journal diameter:45.000 mm (1.7717 in)

Cylinder head

Cylinder head
Valve Arrangement:DOHC, chain-driven
Valves:16 (4 valves per cylinder)
Intake/Exhaust duration:
Valve head diameter:INTAKE33.0 mm (1.2992 in)
EXHAUST30.5 mm (1.2008 in)
Valve steam diameter:INTAKE5.975-6.000 mm (0.2352-0.2362 in)
EXHAUST5.960-6.000 mm (0.2346-0.2362 in)

Maintenance data

Oil system
Recommended engine oilSAE 5W-30, 10W-40
Oil typeAPI SG or SF and better
Engine oil capacity (Refill capacity)4.8 L (5.07 US. qt, 4.22 Imp. qt.)
Ignition system
Spark plugBosch F7LDCR, Champion RC8DMC, NGK BKR6EK
Spark plug gap:0.9 mm (0.0354 in)

Vehicle applications

ModelYears Produced
BMW 318is (E30)1989–1991
BMW 318i (E30)1990–1992
BMW 318i (E36)1992–1995
BMW 318is (E36)1991–1995
BMW 318ti (E36)1994–1995
Author: Sergei Wers
About: Co-founder and CEO of a multi-brand auto repair shop (engine repair, chassis repair, body repair and painting) for over 15 years. I have been developing internet sites with technical specifications for more than seven years.

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We try to use verified sources and official documentation, however, differences between sources or errors in entering information may occur. We do not provide advice on technical issues related to the engines operation or repair. We do not recommend using provided information for engines repairing engines or spare parts ordering, use only official service manuals and spare-parts catalogs.

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