Mercedes-Benz M112 V6 petrol engine

Mercedes-Benz / AMG
Manufacturer:	Mercedes-Benz / AMG
Production period:	1997-2005
Style:	V , six-cylinder
Engines:	2.4 liters (2398 cc)  to 3.7 liters (3724 cc)
Previous model:	M 104
Successor:	M 272

The M 112 is a V6 - gasoline engine from Mercedes-Benz , which in March 1997 in the E-Class of the 210 series was introduced. This replaced the M 104 . In 2004, the successor M 272 was introduced.

The M 112 is technically closely related to the V8 M 113 . Both have a cylinder spacing of 106 mm and an angle of 90 ° between the cylinder banks. They can be made in large part on the same production facilities, and there are many identical parts. Both have an engine block made of light alloy with cast-in cylinder liners made of Silitec ( Al - Si - alloy ), and a light alloy cylinder head having an overhead camshaft per cylinder bank.

The four-bearing crankshaft has split crank pins for uniform firing intervals of 120 ° crank angle. They sit directly next to each other without intermediate cheeks in order not to have to increase the offset of the cylinder banks and thus the overall length of the engine. Above the crankshaft in the cylinder V sits a balancer shaft , which rotates counter to the crankshaft at the same speed. As a result, the mass forces and moments of the first order are completely compensated. Camshafts and balance shaft are driven by a double roller chain.

Like the M 113, the M 112 has two intake valves and one exhaust valve per cylinder , which are operated via light metal roller rocker arms with hydraulic lash adjuster. By the single exhaust valve results in a smaller surface of the exhaust passage and thereby less heat emission of the exhaust gas to the cylinder head, especially when the engine is cold. The catalyst thus reaches its operating temperature faster. The thin and double-walled sheet metal exhaust manifolds , which absorb little heat, also contribute to this.

Each combustion chamber has two spark plugs on the right and left of the exhaust valve. The arrangement of valves and candles is symmetrical. The double ignition operates with time-shifted control of the two candles. This achieves a fast and uniform combustion, greater safety against combustion misfires and higher tolerance against  exhaust gas recirculation . Because of the double ignition, the heat load of the pistonis rising, this is cooled by oil spray nozzles, inject the engine oil from below against the piston crown. The candles in each combustion chamber are also controlled from one cycle to the next in alternating order. This results in a more uniform and lower heat load on the piston and even burning of both candles.

M 112 there was with 2.4 to 3.7  liter capacity .