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. The bore spacing on the M103 engine is 97 mm.

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The examples and perspective in this article may not represent a worldwide view of the subject. (December 2010)

Mercedes-Benz M103 engine
Overview
Manufacturer	Mercedes-Benz
Production	1984–1997
Layout
Configuration	Naturally aspirated Straight-6
Displacement	2.6 L; 158.5 cu in (2,597 cc) 3.0 L; 180.6 cu in (2,960 cc)
Cylinder bore	82.9 mm (3.26 in) 88.5 mm (3.48 in)
Piston stroke	80.2 mm (3.16 in)
Valvetrain	SOHC / 2 valves x cyl.
Compression ratio	9.2:1
RPM range
Redline	6200
Combustion
Fuel system	Continuous Injection System - Electronic
Fuel type	Gasoline
Oil system	Wet sump
Cooling system	Water cooled
Output
Power output	118–140 kW (160–190 PS; 158–188 hp)
Torque output	220–260 N⋅m (162–192 lb⋅ft)
Chronology
Predecessor	M110
Successor	M104

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 (300E), W126 (300SE / 300SEL), R107 (300SL), R129 (300SL), W463 (300GE), and Isdera Spyder 036i.

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 (190E 2.6), W124 (260E / 300E 2.6) and W126 (260SE).

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