In the heavy-duty commercial vehicle market in Japan, particularly in the segment of dump trucks and tractors, naturally aspirated engines maintain a dominant market share because of their superior torque characteristics in the low speed range.
In order to meet the ever increasing needs for higher speeds of transportation, better fuel economy and higher reliability, and the needs for increasingly strict exhaust emission regulations, Mitsubishi Motors Corporation (MMC) has developed the 8M20, a 20 liter V8 diesel engine.
The '92 model series of “THE GREAT”, MMC's main heavy-duty trucks, has featured this new and powerful engine and has been in the market place since October, 1991.
The 8M20 is a naturally aspirated engine that provides an output of 294kW/2200rpm, complying with the current Japanese exhaust emission regulations. It has a 4-valve/cylinder structure and tappets with a needle roller bearing for reduction of mechanical losses, thereby achieving minimum brake specific fuel consumption of 211 g/kWh under full load condition.
In order to assure sufficient engine brake performance corresponding to the higher output, MMC, in collaboration with Jacobs Vehicle Equipment Company (Jacobs) in the U.S.A., has developed the Mitsubishi “POWERTARD”. The “POWERTARD” is a combination of the Jake Brake and the conventional Mitsubishi exhaust brake, making it possible to offer excellent driveability.
This paper describes the design and development of the 8M20 engine.