OM401

The 400 series obeyed a strict rule: one bank angle, one bore, and each engine one cylinder pair and one crank throw longer than the last, so that all of them could be machined on a single line. Every crankpin carried two opposing big ends. For the V8 that geometry produced even firing intervals; for a V6 at the same 90° it did not, and Daimler-Benz accepted the rough running on the grounds that a lorry is not a car. What the 9.6-liter, 192 PS six gave in exchange was very low weight and very compact dimensions.

From 1973 it worked in the middle of the New Generation range — the 1219, 1419, 1619, 1719 and 2219 — and in the O 303 coach, where it was the entry engine. The vibration was designed out only in the OM 44x generation from 1985, whose OM 441 used a crankshaft with offset crankpins. The OM 401 itself had one turn left: with naturally aspirated engines unable to meet the coming limits, it came back between 1991 and 1994 as the turbocharged, intercooled OM 401 LA at 245, 272 and 313 PS — a Euro I V6 doing work that had belonged to an atmospheric V8.