Quote:
Originally Posted by maxnix
I think you are forgetting about the old mechanical injection pumps such as the Spica (ALFA Romeo) and Kugelfischer (BMW and Porsche), although both were port injected. The former was an adaptation of a diesel unit that operated at 1300 - 1500 psi, and I cannot recall the operating pressures of the Kugelfischer, but it is much higher than the Bosch electro mechanical injectors that replaced it.
I don't understand how higher line pressure dilutes fuel, but perhaps you meant that the fuel dilutes the cylinder wall lubrication which always occurs, especially in over rich conditions. If your hypothesis is true, one wonders why we don't see the same thing in Diesel engines as the direction injection design is much the same and the cylinder pressures are even higher.
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I believe the dilution of the oil comes partly from cylinder wall wash down and partly from blow by. Whatever the mechanism, I've seen higher fuel dilution in my N54 than in any other BMW I've ever done UOAs on (all port injected naturally aspirated), and the phenomenon appears to be an accepted fact as far as I can tell. Maybe I don't know or haven't explained the theory properly. Not sure about diesels but I believe they too have fuel dilution but it may not be so much of a problem because diesel fuel is fuel OIL. I have seen recommended limits for gas dilution in oil of 2% max, but up to 6% max for diesels.
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