All MB diesels up to the TDI use pre-chamber injection rather than direct injection, so fuel reaching the cylinder walls isn't an issue, by and large.

There are several prechamber designs, with associated piston top shapes, not interchangeable. The appearance is basically an off-center hole with flow channels radiating from it. Prechamber has several holes, I don't remember how many at the moment.

The TDI pistons have a "chamber" in them, unlike older direct injection diesels, and I don't know just exactly what the nozzle lookes like -- the older DI nozzles had four holes at a right angle to the axis of the nozzle, while the MB injector for the prechamber diesels has a waisted pintle, injects directly out the axis of the nozzle.

The new nozzles also inject a very small amount fuel before the main injection -- this ignites, so that the main fuel charge is injected into a burning fuel mix. reduces knock and soot considerably, but makes the nozzles EXPENSIVE ($600 or so each).

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!