The BMW M21D24 is a 2.4 liters (2,443 cc, 149.1 cu-in) straight-six, four-stroke cycle naturally aspirated or turbocharged diesel engine from BMW M21-family. This engine is based on the M20 gasoline engine. The engine was manufactured on Steyr Plant (Upper Austria) since 1983 to 1992.
The BMW M21D24 engine features a cast-iron block and aluminum head with a single overhead camshaft (SOHC) and two valves per cylinder (12 in total). It has swirl chamber injection. Cylinder bore and piston stroke are 80.0 mm (3.15 in) and 81.0 mm (3.19 in), respectively. Compression ratio rating is 22.0:1.
An early version of this engine was turbocharged. It used the Garrett T03 turbocharger (without an intercooler) and mechanically controlled fuel pump. This engine produced 115.6 PS (85.0 kW; 114.0 HP) at 4,800 rpm of output power and 210 N·m (21.4 kg·m, 154.8 ft·lb) at 2,400 rpm of torque. Since 1987, the M21D24 engine was equipped with an electronically controlled fuel pump (BoschEDC management system), which increased the torque to 220 N·m (22.4 kg·m, 162.4 ft·lb) at 2,400 rpm.
In 1985, BMW introduced the naturally aspirated version of the M21D24, which produces 85.7 PS (63.0 kW; 85.0 HP) at 4,600 rpm of horsepower and 152 N·m (15.5 kg·m, 112 ft·lb) at 2,500 rpm of peak torque.
The breakdown of the engine code is as follows:
- M21 – Engine Family
- D – Diesel
- 24 – 2.4 Liter Displacement
General information
| Engine Specifications | |
| Engine code | M21D24 |
| Layout | Four stroke, Inline-6 (Straight-6) |
| Fuel type | Diesel |
| Production | 1983-1992 |
| Displacement | 2.4 L, 2,443 cc (149.1 cu in) |
| Fuel system | Before 1987: Mechanically controlled fuel pump After 1987: Electronically controlled fuel pump (BoschEDC) |
| Power adder | Garrett T03 turbocharger |
| Max. horsepower | Naturally aspirated: 85.7 PS (63.0 kW; 85.0 HP) at 4,600 rpm Turbo: 115.6 PS (85.0 kW; 114.0 HP) at 4,800 rpm |
| Max. torque | Naturally aspirated: 152 N·m (15.5 kg·m, 112 ft·lb) at 2,500 rpm Turbo: 210 N·m (21.4 kg·m, 154.8 ft·lb) at 2,400 rpm 220 N·m (22.4 kg·m, 162.4 ft·lb) at 2,400 rpm |
| Firing order | 1-5-3-6-2-4 |
| Dimensions (L x H x W): | – |
| Weight | – |
Cylinder block
| Cylinder block | ||
| Cylinder block alloy | Cast-iron | |
| Compression ratio: | 22.0:1 | |
| Cylinder bore: | 80.0 mm (3.15 in) | |
| Piston stroke: | 81.0 mm (3.19 in) | |
| Number of piston rings (compression / oil): | 2 / 1 | |
| Number of main bearings: | 7 | |
| Cylinder inner diameter (standard): | 80.000 mm (3.1496 in) | |
| Piston skirt diameter (standard): | 79.965 mm (3.1482 in) | Piston ring side clearance: | Top | – |
| Second | 0.050-0.080 mm (0.002-0.0031 in) | |
| Oil | 0.030-0.060 mm (0.0012-0.0024 in) | |
| Piston ring end gap: | Top | 0.200-0.400 mm (0.0079-0.0157 in) |
| Second | 0.200-0.400 mm (0.0079-0.0157 in) | |
| Oil | 0.250-0.500 mm (0.0098-0.0197 in) | |
| Crankshaft journal diameter: | 60.000 mm (2.3622 in) | |
| Crankpin diameter: | 44.975-44.991 mm (1.7707-1.7713 in) | |
Cylinder head
| Cylinder head | ||
| Valve Arrangement: | SOHV, belt drive | |
| Valves: | 12 (2 valves per cylinder) | |
| Intake/Exhaust duration: | – | |
| Valve head diameter: | INTAKE | 35.000 mm (1.378 in) |
| EXHAUST | 31.000 mm (1.2205 in) | |
| Valve steam diameter: | INTAKE | 7.000 mm (0.2756 in) |
| EXHAUST | 7.000 mm (0.2756 in) | |
Maintenance data
| Valve clearance | |
| Intake valve (HOT) | 0.35 mm (0.0138 in) |
| Exhaust valve | 0.35 mm (0.0138 in) |
| Compression pressure | |
| Minimum | 20.4 kg/cm2 (20.0 bar, 290 psi) |
| Oil system | |
| Recommended engine oil | 5W-30, 10W-30 |
| Oil type | Semi-synthetic |
| Engine oil capacity (Refill capacity) | 5.8 L (6.13 US. qt, 5.1 Imp. qt.) |
| Ignition system | |
| Glow plug | Bosch 0 205 201 008, Champion CH159, Lucas/CAV HDS218 |
Vehicle applications
| Model | Years Produced |
| BMW 524td (E28) | 1983-1988 |
| BMW 524d (E28) | 1985-1988 |
| BMW 524td (E30) | 1985-1993 |
| BMW 524d (E30) | 1985-1993 |
| BMW 524td (E34) | 1988-1991 |
| Continental Mark VII | 1984-1985 |
| Lincoln Continental | 1984-1985 |
| Vixen 21 TD and Vixen 21 XC | 1986-1987 |
| Bertone Freeclimber | 1989 – 1991 |
| UMM Alter II | 1992 |
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