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 spherical combustion chamber to a "heart shaped" combustion chamber.

Mercedes-Benz M103 engine
Overview
Manufacturer	Mercedes-Benz
Production	1984–1997
Layout
Configuration	Naturally aspirated Inline-6
Displacement	158.6 cu in (2,599 cc) 180.8 cu in (2,962 cc)
Cylinder bore	82.9 mm (3.264 in) 88.5 mm (3.484 in)
Piston stroke	80.25 mm (3.159 in)
Valvetrain	SOHC / 2 valves x cyl.
Compression ratio	9.2:1
RPM range
Max. engine speed	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 & M123
Successor	M104

An egg being cooked on a 3.0 L M103 engine

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
Layout
Configuration	Straight-six
bore pitch	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)
Displacement	2,599 cc (158.6 cu in)	2,962 cc (180.8 cu in)
Max. engine speed	6,200/min
Combustion
Principle	Internal combustion engine
Mode of operation	Four-stroke
Fuel type	gasoline
Fuel octane	95 RON/85 MON · 91 RON/81MON via plug-in jumper located in the engine compartment
Fuel system	CIS-E (Continuous Injection System)
Ignition system	electronic engine control unit
Firing order	1–5–3–6–2–4
Valvetrain	SOHC
Valves per cylinder	2
Configuration	V-shaped overhead crossflow
Camshaft drive	simple roller-type chain
Aspiration	Naturally aspirated
Compression ratio	9.2 : 1
Management
Lubrication	pressure circulation with Wet sump
Oil capacity	6 L (1.6 US gal; 1.3 imp gal)
Cooling	water cooled engine cooling
Coolant capacity	8.5 litres (2.2 US gal; 1.9 imp gal)
Starter motor	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 103
Type	102.92X–96X	102.98X	103.940	103.980
Configuration	Straight-four		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)
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)
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)