BMW M42B18

BMW M42B18The BMW M42B18 is a 1.8 L (1,796 cc, 109.6 cu·in) straight-four natural aspirated four-stroke liquid-cooled internal combustion gasoline engine, manufactured by Bayerische Motoren Werke AG from 1989 to 1996.

A 84.0 mm (3.31 in) cylinder bore and 81.0 mm (3.19 in) piston stroke give the M42B18 engine a total of 1,796 cc of displacement. The compression ratio rating is 10.0:1.

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 E30 model, 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 E36 model.

The BMW M40B18 features:

  • Cast-iron cylinder block
  • Crankshaft with eight counterweights
  • Aluminum cylinder head
  • Chain-driven double overhead camshafts (DOHC)
  • Low-maintenance timing chain with a self-adjusting hydraulic chain tensioner
  • 16 valves (4 per cylinder) with hydraulic tappets
  • Multi Point Fuel Injection (MPFI)
  • Bosch Motronic M 1.7 engine management system
  • “Coil-on-plug” ignition system with fully electronic controlled ignition timing
  • Dual length intake manifold (BMW “DISA” system) for later versions
  • Pressurized lubrication system
  • Liquid-cooled cooling system

General information

Engine Specifications
Engine model M42B18
Production 1989-1996
Engine type 4-stroke, DOHC, inline-4
Displacement 1.8 L, 1,796 cm3, (109.6 cu·in)
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
Cooling system Liquid-cooled
Lubricating system Pressurized lubrication
Fuel system Multi Point Fuel Injection (MPFI)
Engine management system Bosch Motronic M 1.7
Starting system Electric starter 12V
Firing order: 1-3-4-2
Dimensions (L x W X H)
Dry weight

Cylinder Block and Head

Cylinder block
Cylinder block alloy: Cast-iron
Compression ratio: 10.0:1
Cylinder bore: 84.0 mm (3.31 in)
Piston stroke: 81.0 mm (3.19 in)
Cylinder internal diameter (standard): 84.000-84.014 mm (3.3071-3.3076 in)
Piston skirt outer diameter (standard): 83.985 mm (3.3065 in)
Number of piston rings (compression / oil): 2/1
Connecting rod big end diameter (standard): 28.000 mm (1.1024 in)
Connecting rod small end diameter (standard): 22.0050-22.0120 mm (0.8663-0.8666 in)
Piston pin diameter: 22.000 mm (0.8661 in)
Side clearance (Top): 0.020-0.200 mm (0.0008-0.0079 in)
Side clearance (Second): 0.020-0.100 mm (0.0008-0.0039 in)
Side clearance (Oil): 0.020-0.100 mm (0.0008-0.0039 in)
Ring end gap (Top): 0.200-1.000 mm (0.0079-0.0394 in)
Ring end gap (Second): 0.200-1.000 mm (0.0079-0.0394 in)
Ring end gap (Oil): 0.200-1.000 mm (0.0079-0.0394 in)
Number of main bearings: 5
Crankshaft main journal diameter: 60.000 mm (2.3622 in)
Crankpin journal diameter: 45.000 mm (1.7717 in)
Crankshaft center distance: 40.5 mm (1.595 in)
Cylinder head
Cylinder head alloy: Aluminium
Valve arrangement: DOHC, chain driven
Valves: 4 ,(16 valves in total)
Head height: 139.550-140.000 mm (5.4941-5.5118 in)
Valve head diameter (INTAKE): 33.0 mm (1.2992 in)
Valve head diameter (EXHAUST): 30.5 mm (1.2008 in)
Valve steam diameter (INTAKE): 5.975-6.000 mm (0.2352-0.2362 in)
Valve steam diameter (EXHAUST): 5.960-6.000 mm (0.2346-0.2362 in)

Service Data

Compression pressure
Standard: 10-11 bar (10.1-11.2 kg/cm2; 145-160 psi)
Oil system
Lubrication system: Pressurized lubrication
Oil type: API SG or SF and better
Recommended oil: SAE 10W-40, 5W-30
Oil capacity: 4.8 L (5.07 US. qt, 4.22 Imp. qt.)
Oil pressure: 0.5 bar (0.51 kg/cm3; 7.25 psi) at Idle speed
4.3 bar (4.3 kg/cm3; 64.4 psi) at Rated speed
Ignition system
Type: Electronic “Coil-on-plug” ignition system
Spark plug: Bosch F7LDCR, Champion RC8DMC, NGK BKR6EK
Spark plug gap: 0.9 mm (0.0354 in)
Spark plug torque: 27 N·m (2.8 kg·m, 19.9 ft·lb)


Model Years 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


1. BMW TIS (Technical Information System)

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 official documentation and verify the published data, but errors may occur. In addition, specifications of machinery and equipment may vary depending on markets and modifications. We do not recommend the use of this data for spare parts or repairs. Use official service manuals or parts catalogs for your product.

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