Mercedes-Benz OM629 engine

Mercedes-Benz OM629
Overview
Manufacturer	Mercedes-Benz
Production	2005–2010
Layout
Displacement	4.0 L (3,996 cc)
Cylinder bore	86.0 mm
Piston stroke	86.0 mm
Cylinder block alloy	Aluminium alloy
Valvetrain	DOHC
Compression ratio	17:1
Combustion
Turbocharger	Twin-turbo
Fuel system	Common rail
Fuel type	Diesel
Chronology
Predecessor	Mercedes-Benz OM628 engine

The Mercedes-Benz OM629 is a 4.0-litre diesel-fuelled, 4-stroke, compression-ignition internal combustion 75° 32-valve V8 engine used in the 2000s. It is the world’s first aluminium V8 diesel engine.^[1]

Design

The block features an aluminium crankcase and cylinder heads. It uses aluminium sand casting in bedplate construction (divided at the height of the crankshaft) with wet cylinder liners made of cast iron.

The main bearings are reinforced, cast in GGG ductile cast iron. Rather than the usual 90° "vee" angle between the cylinder banks, a 75° angle was chosen due to the space available to install the engine.^[2] The consequence of this specific angle is free inertial forces of the first order. To compensate for this, the OM628 and OM629 use a balancer shaft located in the vee of the engine. To ensure even firing intervals the crankshaft uses split crank pins.The engine uses 97.0 mm cylinder spacing.

The engine uses double overhead camshafts (DOHC) on each bank (‘quad-cam’) with four valves per cylinder, operated by hydraulic tappets. Each cylinder bank uses a variable geometry turbocharger. The compressed air from these is cooled by an air to water heat exchanger with an additional cold water circuit.

Compared to the OM628, the OM629 engine has an improved common-rail system,^[3] and higher boost from the turbochargers. It displaces 4.0L (3996cc) and produces between 225 kW (302 hp) to 235 kW (315 hp) at 3600 rpm, and 700 N⋅m (516 lb⋅ft) to 730 N⋅m (538 lb⋅ft) of torque between 2000–2600 rpm.

Models

References