Mercedes-Benz M103 engine

The Mercedes-Benz M103 was a straight-6 15 degrees, crossflow cylinder head with an inclination to the right, automobile engine produced from 1984 to 1997. It was a single overhead cam design with 2 valves per cylinder. The M103 was replaced by the M104 starting in 1989. The bore spacing on the M103 engine is 97 mm.

Mercedes-Benz M103 engine
Overview
ManufacturerMercedes-Benz
Production1984 to 1997
Layout
ConfigurationNaturally aspirated Straight-6
Displacement2.6 L; 158.5 cu in (2,597 cc)
3.0 L; 180.6 cu in (2,960 cc)
Cylinder bore82.9 mm (3.26 in)
88.5 mm (3.48 in)
Piston stroke80.2 mm (3.16 in)
ValvetrainSOHC 2 valves x cyl.
Compression ratio9.2:1
RPM range
Redline6200
Combustion
Fuel systemContinuous Injection System - Electronic
Fuel typeGasoline
Oil systemPressure circulation
Cooling systemWater cooled
Output
Power output118–140 kW (160–190 PS; 158–188 hp)
Torque output220–260 N⋅m (162–192 lb⋅ft)
Chronology
PredecessorM110
SuccessorM104

3.0 L

The 103.980 engine of 3.0 L; 180.6 cu in (2,960 cc) uses the CIS-E (Continuous Injection System - Electronic).

Specifications
  • Engine power @ 5700 rpm: 132 kW (179 PS; 177 hp) with catalyst, 140 kW (190 PS; 188 hp) without catalyst
  • Torque @ 4400 rpm: 255 N⋅m (188 lb⋅ft) (with catalyst), 260 N⋅m (192 lb⋅ft) without catalyst
  • Bore and stroke: 88.5 mm × 80.2 mm (3.48 in × 3.16 in)
  • Compression ratio: 9.2:1
  • Redline: 6200 rpm
  • Firing order: 1-5-3-6-2-4
  • Lubrication system: pressure circulation
  • Oil capacity: 6 litres (1.6 US gal; 1.3 imp gal)
  • Coolant capacity: 8.5 litres (2.2 US gal; 1.9 imp gal)
  • Number of valves: 1 intake, 1 exhaust with V-shaped overhead configuration
  • Valve operation: 1 top camshaft.
  • Camshaft drive: simple roller-type chain
  • Starter motor: 1.5 kW electrical motor; since Jan 1988: 1.7 kW
  • Ignition system: electronic ignition system.
  • Recommended fuel octane: 91 RON/MON (96 RON) (86 MON).

This engine can be found in the W124 E-Class, W126 S-Class, Mercedes-Benz R129, W463 G-Class and the R107.

2.6 L

The smaller 103.940 engine of 2.6 L; 158.5 cu in (2,597 cc) also used the CIS-E engine management system.

Specifications
  • Engine power @ 5800 rpm: 118 kW (160 PS; 158 hp) with catalyst, 124 kW (169 PS; 166 hp) without catalyst
  • Torque @ 4600 rpm: 220 N⋅m (162 lb⋅ft) with catalyst, 228 N⋅m (168 lb⋅ft) without catalyst.
  • Bore and stroke: 82.9 mm × 80.2 mm (3.26 in × 3.16 in)
  • Compression ratio: 9.2:1
  • Redline: 6200 rpm
  • Firing order: 1-5-3-6-2-4
  • Lubrication system: pressure circulation
  • Oil capacity: 6 litres (1.6 US gal; 1.3 imp gal)
  • Coolant capacity: 8.5 litres (2.2 US gal; 1.9 imp gal)
  • Camshaft drive: simple roller-type chain
  • Number of valves: 1 intake, 1 exhaust with V-shaped overhead configuration
  • Valve operation: 1 top camshaft
  • Starter motor: 1.5 kW electrical motor; since Jan 1988: 1.7 kW
  • Ignition system: electronic ignition system.

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.

This engine can be found in the W201 (190), W124 E-Class and W126 S-Class.

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