OM352

Direct injection had been the highest priority in Stuttgart since 1956, when Alfred Müller-Berner was recruited from Leyland to lead the work; the pre-chamber engines it was meant to displace had been bored out until their chambers stood at the limit of what they could survive thermally. His answer used swirl inlet ports, a four-hole injector in the center of the chamber and a cylindrical bowl in the piston. When the 5.7-liter six was finally ready in 1963 the engine plant could not keep pace — that first year's output went almost entirely to truck assembly at Wörth, and only from the summer of 1964 was it freely available.

A turbocharged OM 352 A followed in 1966, and intercooling later still. It became the engine of the Unimog: the 406, 416, 419, 425, 426 and 435 all used it, more than 35,000 times in the 406 alone. Mannheim built it from 1963 and licensees around the world from 1970 — some 180,000 in Iran by itself — and more than 300,000 were made in all, which by the late 1970s put it among the most common truck engines in West Germany. New emissions limits at the start of the 1990s ended it, its development potential by then largely spent.