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 M40-family. The engine was manufactured from 1987 to 1994.
The M40B18 engine features a cast-iron cylinder block, a cast crankshaft with eight counterweights and cross-flow aluminum head with a belt-driven single overhead camshaft (SOHC) and two valves per cylinder (8 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 8.8:1.
This engine used a Multi Point Fuel Injection system (MPFI) and the Bosch Motronic M 1.3 engine management system for BMW E30 or Bosch Motronic M 1.7 for BMW E36 model. Redline is 6,200 rpm.
The BMW M40B18 engine produced 113.0 PS (83.0 kW; 111.0 HP) at 5,500 rpm of maximum output power and 162 N·m (16.5 kg·m, 119.4 ft·lb) at 4,250 rpm of peak torque for BMW 318i (E30) model, or 115.6 PS (85.0 kW; 114.0 HP) at 5,500 rpm of horsepower and 165 N·m (16.8 kg·m, 121.6 ft·lb) at 4,250 rpm of torque for BMW 318i (E36).
The breakdown of the engine code is as follows:
- M40 – Engine Family
- B – Gasoline
- 18 – 1.8 Liter displacement
General information
| Engine Specifications | |
| Engine code | M40B18 |
| Layout | Four stroke, Inline-4 (Straight-4) |
| Fuel type | Gasoline |
| Production | 1987-1994 |
| Displacement | 1.8 L, 1,796 cc (109.6 cu in) |
| Fuel system | Multi Point Fuel Injection (MPFI) |
| Power adder | None |
| Max. horsepower | E30: 113.0 PS (83.0 kW; 111.0 HP) at 5,500 rpm E36: 115.6 PS (85.0 kW; 114.0 HP) at 5,500 rpm |
| Max. torque | E30: 162 N·m (16.5 kg·m, 119.4 ft·lb) at 4,250 rpm E36: 165 N·m (16.8 kg·m, 121.6 ft·lb) at 4,250 rpm |
| Firing order | 1-3-4-2 |
| Dimensions (L x H x W): | – |
| Weight | – |
Cylinder block
| Cylinder block | ||
| Cylinder block alloy | Cast-iron | |
| Compression ratio: | 8.8:1 | |
| 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) | |
| 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) | |
| Crankshaft journal diameter: | 60.000 mm (2.3622 in) | |
| Crankpin journal diameter: | 45.000 mm (1.7717 in) | |
Cylinder head
| Cylinder head | ||
| Valve Arrangement: | SOHC, belt-driven | |
| Valves: | 8 (2 valves per cylinder) | |
| Intake/Exhaust duration: | – | |
| Valve head diameter: | INTAKE | 42.000 mm (1.6535 in) |
| EXHAUST | 36.000 mm (1.4173 in) | |
| Valve steam diameter: | INTAKE | 6.975-7.000 mm (0.2746-0.2756 in) |
| EXHAUST | 6.960-7.000 mm (0.274-0.2756 in) | |
Maintenance data
| Oil system | |
| Recommended engine oil | SAE 5W-30, 5W-40 |
| Oil type | API SG or SF and better |
| Engine oil capacity (Refill capacity) | 4.0 L (4.23 US. qt, 3.52 Imp. qt.) |
| Ignition system | |
| Spark plug | Bosch F8LCR, Champion C9YCC, NGK ZFR5F-11 |
| Spark plug gap: | 0.7-0.9 mm (0.0276-0.0354 in) |
Vehicle applications
| Model | Years Produced |
| BMW 318i (E30) | 1987–1994 |
| BMW 318i (E36) | 1992–1993 |
| BMW 518i (E34) | 1989–1994 |
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