The 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 code | M42B18 |
| Layout | Four stroke, Inline-4 (Straight-4) |
| Fuel type | Gasoline |
| Production | 1989-1996 |
| Displacement | 1.8 L, 1,796 cc (109.6 cu in) |
| Fuel system | Multi Point Fuel Injection (MPFI) |
| Power adder | None |
| 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 order | 1-3-4-2 |
| Dimensions (L x H x W): | – |
| Weight | – |
Cylinder block
| Cylinder block | ||
| Cylinder block alloy | Aluminum | |
| 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: | Top | 0.020-0.200 mm (0.0008-0.0079 in) |
| Second | 0.020-0.100 mm (0.0008-0.0039 in) | |
| Oil | 0.020-0.100 mm (0.0008-0.0039 in) | |
| Piston ring end gap: | Top | 0.200-1.000 mm (0.0079-0.0394 in) |
| Second | 0.200-1.000 mm (0.0079-0.0394 in) | |
| Oil | 0.200-1.000 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: | INTAKE | 33.0 mm (1.2992 in) |
| EXHAUST | 30.5 mm (1.2008 in) | |
| Valve steam diameter: | INTAKE | 5.975-6.000 mm (0.2352-0.2362 in) |
| EXHAUST | 5.960-6.000 mm (0.2346-0.2362 in) | |
Maintenance data
| Oil system | |
| Recommended engine oil | SAE 5W-30, 10W-40 |
| Oil type | API SG or SF and better |
| Engine oil capacity (Refill capacity) | 4.8 L (5.07 US. qt, 4.22 Imp. qt.) |
| Ignition system | |
| Spark plug | Bosch F7LDCR, Champion RC8DMC, NGK BKR6EK |
| Spark plug gap: | 0.9 mm (0.0354 in) |
Vehicle applications
| 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 |
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