Mercedes-Benz OM352 engine
The Mercedes Benz OM352 Engine is a 5675 cm3 (5.7 litres, 345-cubic-inch) displacement inline 6-cylinder 4-stroke Diesel engine.
It is one of many motors in the 300 series of engines, which were developed during and after World War II, while specifically the OM352 was revealed in 1964. The OM352's lineage can be traced back to the OM312, itself an 80HP inline-six engine. The OM352 has many applications, including marine, military, municipal, and agricultural vehicles, as well as stationary settings. The engine has differing trim and power levels, affording designations such as OM 352A a variant fitted with a turbocharger, or the OM 352LA, which is fitted with an intercooler and a turbocharger. (List of Mercedes-Benz engines.)
The engine is water-cooled, and is produced using cast-iron cylinder block, with cast-in cylinders. The engine utilizes diesel fuel delivered in a direct injection method from a Bosch PES style inline injection pump. The cylinder head is a single unit for all cylinders, and the cylinder head cover and air intake are shared by a single cast aluminum alloy. Interestingly, exhaust ports 2&3 and 4&5 are siamesed together, presenting an exhaust manifold with only four outlets.
The crankshaft is a precision forged unit running in seven three-layer bearings, with counterweights bolted onto the crank webs, much like any other diesel motor of its vintage. The middle bearing is also the thrust bearing. The connecting rods are of a split design, with bronze bushings for the piston pin.
The OM 352 was also one of many Mercedes engines licensed in 1979 for manufacture by Atlantis Diesel Engines (ADE) in South Africa. These were known as ADE 352 and are virtually identical to the Mercedes engines. Recently the OM 352 was licensed by TATA for use in their 713S Trucks. These are manufactured by TATA but however have slight differences like the weights no longer being bolted to but rather part of the crank and no holes for oil sprayers in the block. These modifications are likely to reduce complexity and cost of engine production.
Common output power can vary from 92 kW to 141 kW (126 to 192 hp) depending on the fuel delivery and air charge options. Higher output can be achieved through special modifications, however engine longevity may be affected with such non-factory modifications.
Improved engines developed after the OM352 include the OM366, which looks extremely similar in appearance. Due to emissions requirements, the 300 series engines were eventually retired. Mercedes Benz 900 series engines are the successors of motors such as the OM352.
|Mercedes Benz Type||352|
|Combustion System||Four-stroke diesel with direct injection|
|Number of cylinders, Cylinder arrangement||6, vertical in-line|
|Total displacement||5657 cm2|
|Compression at starting speed||22 bar up to 24 bar (2.2 to 2.4 MPa), minimum 20 bar|
|Continuous output at nominal speed||96 kW (130 hp) @ 2800 rpm|
|Maximum torque at speed||363 N·m (267 ft·lbf) @ 1700 rpm|
|Idle Speed||700 rpm|
|Start of fuel delivery before TDC||18 degrees|
|Cylinder Firing Order||1 - 5 - 3 - 6 - 2 - 4|
|Valve Clearance, cold||(inlet 0.20 mm) (exhaust 0.30 mm)|
|Exhaust manifold pressure||5 bar - 7 bar|
|Opening pressure of injection nozzles||200 bar (20 MPa) + 10 (new), 180 bar minimum (used)|
|Operating temperature||80 degrees Celsius|
|Oil pressure||nominal 2–5 bar (200–500 kPa), idle min 0.6 bar|
|Weight, dry||460 kg, 1014 lb|
- Information from the Unimog 435 Workshop manual, Book 1 Section 1.2/1