# Mercedes-Benz M103 engine

The Mercedes-Benz M103 is a straight-6 15 degrees, crossflow cylinder head with an inclination to the right, automobile engine produced from 1984 to 1997. It is a single overhead cam design with 2 valves per cylinder. The M103 was replaced by the M104 starting in 1989. This engine received several updates over the years of production, one of the updates was a change from a "heart shaped" to a "HEMI" spherical combustion chamber.

## Specifications

The only mechanical differences from the M103 3.0 L to the M103 2.6 L were the smaller bore and intake valves, with a slightly different airbox. The CIS-E components between 2.6 and 3.0 variants are all shared for any given model year with the exception of the ECU making engine swaps from 2.6 to 3.0 virtually bolt-in.
| Model | 260 | 300 |
| Type | 103.940 | 103.980 |
| Production period | 1984–1997 | 1984–1997 |
| Layout |||
| Configuration | Straight-six | Straight-six |
| bore pitch | 97 mm (3.819 in) | 97 mm (3.819 in) |
| Cylinder bore | 82.9 mm (3.264 in) | 88.5 mm (3.484 in) |
| Piston stroke | 80.25 mm (3.159 in) | 80.25 mm (3.159 in) |
| Displacement | 2,599 cc (158.6 cu in) | 2,962 cc (180.8 cu in) |
| Max. engine speed | 6,200/min | 6,200/min |
| Combustion |||
| Principle | Internal combustion engine | Internal combustion engine |
| Mode of operation | Four-stroke | Four-stroke |
| Fuel type | gasoline | gasoline |
| Fuel octane | 95 RON/85 MON · 91 RON/81MON via plug-in jumper located in the engine compartment | 95 RON/85 MON · 91 RON/81MON via plug-in jumper located in the engine compartment |
| Fuel system | CIS-E (Continuous Injection System) | CIS-E (Continuous Injection System) |
| Ignition system | electronic engine control unit | electronic engine control unit |
| Firing order | 1–5–3–6–2–4 | 1–5–3–6–2–4 |
| Valvetrain | SOHC | SOHC |
| Valves per cylinder | 2 | 2 |
| Configuration | V-shaped overhead crossflow | V-shaped overhead crossflow |
| Camshaft drive | simple roller-type chain | simple roller-type chain |
| Aspiration | Naturally aspirated | Naturally aspirated |
| Compression ratio | 9.2 : 1 | 9.2 : 1 |
| Management |||
| Lubrication | pressure circulation with Wet sump | pressure circulation with Wet sump |
| Oil capacity | 6 L (1.6 US gal; 1.3 imp gal) | 6 L (1.6 US gal; 1.3 imp gal) |
| Cooling | water cooled engine cooling | water cooled engine cooling |
| Coolant capacity | 8.5 litres (2.2 US gal; 1.9 imp gal) | 8.5 litres (2.2 US gal; 1.9 imp gal) |
| Starter motor | 1.5 kW electrical motor · since Jan 1988: 1.7 kW | 1.5 kW electrical motor · since Jan 1988: 1.7 kW |
| Performance |||
| Power w/ catalyst | 160 PS (118 kW; 158 hp) | 180 PS (132 kW; 178 hp) |
| @ engine speed | 5,800/min | 5,700/min |
| Torque w/ catalyst | 220 N⋅m (162 lb⋅ft) | 255 N⋅m (188 lb⋅ft) |
| @ engine speed | 4,600/min | 4,400/min |
| Power w/o catalyst | 170 PS (125 kW; 168 hp) | 190 PS (140 kW; 187 hp) |
| @ engine speed | 5,800/min | 5,700/min |
| Torque w/o catalyst | 228 N⋅m (168 lb⋅ft) | 260 N⋅m (192 lb⋅ft) |
| @ engine speed | 4,600/min | 4,400/min |
| Applications |||
| W201 | 190 E 2.6 |
| W124 | 260 E · 300 E 2.6 | 300 E |
| W126 | 260 SE | 300 SE · 300 SEL |
| R107 SL | | 300 SL |
| R129 SL | | 300 SL |
| W463 | | 300 GE |
| Isdera Spyder 036i | | Isdera Spyder 036i |

## Data accuracy

The M 102 and M 103 engine family has a common piston stroke of 80.25 mm. As only one decimal place is usually given, a large number of publications are in circulation with the incomplete specification of 80.2 mm. This applies in particular to more recent publications after production was discontinued. As a result, the inaccurate figures of 2,597 cc instead of the actual 2,599 cc for the 2.6 l engine and 2,960 cc instead of 2,962 cc for the 3.0 l engine have become established.
| Model | 200 | 230 | 260 | 300 |
| Engine | M 102 | M 102 | M 103 | M 103 |
| Type | 102.92X–96X | 102.98X | 103.940 | 103.980 |
| Configuration | Straight-four | Straight-four | Straight-six | Straight-six |
| Cylinder bore | 89 mm (3.504 in) | 95.5 mm (3.760 in) | 82.9 mm (3.264 in) | 88.5 mm (3.484 in) |
| Complete Piston stroke | 80.25 mm (3.159 in) | 80.25 mm (3.159 in) | 80.25 mm (3.159 in) | 80.25 mm (3.159 in) |
| Accurate Displacement | 1,997 cc (121.9 cu in) 1,996.99 cc (121.864 cu in) | 2,299 cc (140.3 cu in) 2,299.33 cc (140.314 cu in) | 2,599 cc (158.6 cu in) 2,598.93 cc (158.596 cu in) | 2,962 cc (180.8 cu in) 2,961.92 cc (180.747 cu in) |
| Incomplete Piston stroke | 80.2 mm (3.157 in) | 80.2 mm (3.157 in) | 80.2 mm (3.157 in) | 80.2 mm (3.157 in) |
| Inaccurate Displacement | 1,996 cc (121.8 cu in) 1,995.74 cc (121.788 cu in) | 2,298 cc (140.2 cu in) 2,297.90 cc (140.226 cu in) | 2,597 cc (158.5 cu in) 2,597.31 cc (158.498 cu in) | 2,960 cc (180.6 cu in) 2,960.07 cc (180.635 cu in) |