Quote:
Originally Posted by drmiller100
those are precombustion chamber engines, and run with incredibly inefficient parameters.
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Exactly. That was the best technology they had, when super fine spray patterns and high injection pressures were not yet possible because of lack of machining tolerances and "pre-cups" were the only way to make it work. Injection pressure was probably peaking at 4000 psi at rated HP, where even an older TDI (rotary pump) will hit 15000.
Quote:
Originally Posted by hawk2100n
But the best way to drive these cars for max fuel economy is below the onset of boost when possible, which is hard.
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This is because when boost isn't there, the air/fuel control in the fuel pump limits rack travel, AKA fuel quantity per stroke. Electronic engines do a variation of the same by limiting mm3 per stroke until boost reaches a certain level (smoke limiting) and EGR flow reaches a certain level (NOx limiting).