Mercedes-Benz OM668 engine
The Mercedes-Benz OM668 engine is a diesel inline-four engine manufactured by the Mercedes-Benz division of Daimler AG. It was used in the Mercedes-Benz W168 from 1997 to 2004 and the Mercedes-Benz W414 from 2001 to 2005. Description. The OM 668 makes use of the common rail system. Compared to the otto engine M 166 it has 4 valves per cylinder instead of two. Two chain driven overhead camshafts are used. The intake camshaft is driven by a chain, the exhaust camshaft is connected to the intake camshaft with a gear. Another  chain drives the oil pump from the crankshaft. All engines have a turbocharger and all engines with more than power also have an intercooler. In 1997 the OM 668 was the smallest diesel engine by Mercedes-Benz. There are no mechanical differences between the engines, except from the engine, which does not have an intercooler. In 2001, the camshaft and turbocharger were modified slightly. This increased the rated power, but not the torque, due to the weak clutch of the Mercedes-Benz W 168. Without any physical changes to the engine, the power can be increased to only by changing  the software of the ECU. This does not decrease the durability of the robust engine. Due to the increased torque of up to , the clutch of the W 168 may wear out faster, if the rated power is increased. Models. <nowiki>*</nowiki>OM = Oelmotor (diesel engine),668 = engine series, DE = Direkteinspritzung (common rail injection), 17 = approximate Displacement in dl,A = Abgasturbolader (turbocharger),L = Ladeluftkühler (intercooler),red. = reduced power Other applications. The OM668 is the basis for the Thielert Centurion 1.7 aircraft engine.