Assuming that a car is driven in the same manner in terms of being sympathetic to the clutch (no racing starts, no clutch slipping, no sitting on hills using the bite point rather than the handbrake etc.), do you reckon the DMF on a car with an intrisically smooth engine will last longer? The DMF is partly designed to absorb the vibrations of a an inherently rather rough engine (lets say a 4 pot diesel, for the sake of argument).
The 2.2 PSA unit in our Freelander 2 is pretty smooth. Had a '59 plate Mondeo 1.8 TDCi (125ps) as a hire car the other day. Magazines praise the smoothness of the 2.0 TDCi 140ps unit, but this 1.8 engine was pretty coarse and noisy. To be fair, I suspect that it wasn't in the best of health, as there was a really rough, eneven beat to the engine at around 1,250 rpm... Got my wondering whether an engine like this (or perhaps the economical, torquey but fairly rough VAG TDi PD units) would give a DMF more of a hammering than say a Renault DCi, BMW 4 pot or PSA HDi unit?
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As I understand it, the DMF's workload comes from the enormous pressures exerted on each piston on the firing stroke of a modern turbodiesel engine. A common rail fuel system is able to deliver a more progressive rise in cylinder pressure than, say a PD engine, as the injectors are working from a constantly pressurised fuel rail, giving an infinitely open window for injection to take place. A PD system pressurises each injector according to a mechanical system based on cam timing, so can only operate during that time in the engines cycle where sufficient pressure exists in that injector. This limits the ability to deliver fuel in meticulously metered stages and provide the incredible level of control over the burn that gives a good common rail diesel engine such smooth and quiet combustion.
It's logical that an engine whose cylinder pressures rise smoothly will give a DMF an easier time than one whose cylinder pressures rise more sharply.
The 1.8 TDCi can trace its roots back to the old 1.8 Endura diesel in the mk1 Mondeo and mk V Escort. It is nowhere near as sophisticated as the 1.6, 2.0 and 2.2 PSA co-developed units.
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DMF life - effects of smooth v rough engine - DP
