Quote:
Originally Posted by southlight
No, RS4's DI is a socalled "first generation DI" whereas HPI is on of the first second generation DIs.
HPI is a spray-form DI (RS4's DI isn't spray-form) which has the advantage of extended lean-operation. Whereas FSI can save fuel (lean operation) only at low revs and quite low acceleration, the HPI stays in lean operation (=fuel saving) until about 4000rpm. As I said it's a totally new technology. Audi does not offer second generation DI to date.
So I am just as disappointed as Swamp that BMW didn't manage to feature HPI in M3's engine, but hopefully could clarify that it's nothing that Audi (RS4) "has" already.
Best regards, south
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South, actually you are wrong about Audi's DI technology. FSI technology in the RS4 engine is a second generation technology known as tumble/swirl flow guided DI. It uses high pressure spray that is guided by the intake and combustion chamber flow pattern. The main difference between Audi DI and BMW DI is the use of piezoelectric actuated injectors in the BMW system, instead of electromagnetic injectors. Neither of the technologies, however, can be used in lean burn mode in the US, because of the high sulfur content in our fuels. Both technologies provide a fuel economy and power advantage, even in the US. If there is an advantage to HPI, (and there may be due to the way a piezo transducer might be used to shape the fuel charge) it is in the lean burn mode that is not enabled in the US, and only available in the European market.