Mitsubishi Astron engine

The Mitsubishi Astron, also known by its 4G5 petrol and 4D5 diesel codes, is a family of straight-four internal combustion engines that Mitsubishi Motors first built in 1972. Displacement ranged from 1.8 to 2.6 litres, which made it one of the largest four-cylinder engines of its time. The design used a hemispherical cylinder head with a chain-driven single overhead camshaft and two valves per cylinder; United States cars gained a small extra intake "Jet Valve" to run leaner mixtures for lower emissions. In 1975 the Astron 80 introduced the "Silent Shaft" system, the first use of twin balance shafts in a modern engine, based on Frederick Lanchester patents that Mitsubishi had obtained and later licensed to other makers. The diesel 4D5 branch arrived in 1980 as the first turbodiesel in a Japanese passenger car and powered the Pajero and many pickups.