Mercedes-Benz M103 engine
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The Mercedes-Benz M103 was a straight-6 15 degrees inclination to the right; automobile engine produced from 1986 through 1993. It was a single overhead cam design with 2 valves per cylinder. The M103 was replaced by the DOHC M104 starting in 1990.
The 103.980 engine (181 in.³ or 2960 cm³) produces 177 hp or 132 kW at 5700 rpm (with catalyst), 188 hp or 138 kW at 5700 rpm (without catalyst), and has a torque of 188 ft·lbf or 255 N·m at 4400 rpm (with catalyst), 191 ft·lbf or 260 N·m at 4400 rpm (without catalyst). It uses the CIS-E (Continuous Injection System - Electronic) and has a bore of 88.5 mm (3.48 in) and a stroke of 80.2 mm (3.16 in). The compression ratio is 9.2 : 1 with a redline of 6550 rpm in 1987 and 6200 rpm from 1988 on. The firing order is 1-5-3-6-2-4. Lubrication system is pressure circulation lubrication system. Amount of oil in engine is 6.0 litres and amount of coolant is 8.5 litres. Number of valves is 1 intake, 1 exhaust with V-shaped overhead configuration. Valve operation was 1 top camshaft. Camshaft drive was simple roller-type chain. Starter motor is electrical with 1.5 kW; since 01.88 was 1.7 kW. Ignition system is electronic ignition system. Recommended fuel octane for the M103 is 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.
The smaller 103.940 engine (158 in.³ or 2597 cm³) produces 160 hp or 122 kW at 5800 rpm (with catalyst), 166 hp or 124 kW at 5800 rpm (without catalyst), and generates torque at 162 ft·lbf or 220 N·m at 4600 rpm (with catalyst), 168 ft·lbf or 228 N·m at 4600 rpm (without catalyst). It also used the CIS-E engine management system and had a bore of 82.9 mm (3.26 in) and a stroke of 80.2 mm (3.16 in). The only mechanical differences from the M103 3.0 L to the M103 2.6 L were the decrease in bore, smaller intake valves and 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. The Mercedes Benz 722-series automatic gearbox to which it is usually linked (5-speed manuals were available on some models but are quite rare) is calibrated to take off in second gear to reduce "creeping" and provide a smoother ride. The transmission will select 1st only if the selector is in "2" or in case of abrupt acceleration. Other attributes of this transmission include a 2-3 shift delay when the engine is cold in order to speed up catalyst warm-up. 4th gear is a 1:1 ratio meaning that cruising at about 100 km/h (62 mph)generates engine speeds around 3000rpm. This engine can be found in the W201 190 and W124 E-Class, and W126 S-Class.