This valve induced swirl in the intake charge, enabling the use of leaner fuel/air mixtures for lower emissions.

It was designed as a cartridge containing the valve spring and seat which simply screwed into a threaded hole in the head, similar to a spark plug but inside the cam cover.

It followed the designs of Frederick Lanchester, whose original patents Mitsubishi had obtained, and proved influential as Fiat/Lancia, Saab and Porsche all licensed this technology.

As the first turbodiesel to be offered in a Japanese passenger car, it proved popular in the emerging SUV and minivan markets where Mitsubishi was highly successful, until superseded by the 4M4 range in 1993.

Until now it is still in production, but made into a modern powerplant by putting a common rail direct injection fuel system into the engine.

Peak power is 110 PS (81 kW) at 5000 rpm,[4] as fitted to the Rosa bus or the Canter cabover truck.

The original engine featured a Mikuni two-barrel carburetor with a secondary vacuum actuator; later versions adopted EFI.