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      06-18-2013, 05:35 PM   #9
N8N
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Drives: 2009 E92 335i 6MT
Join Date: Sep 2012
Location: Sterling, VA

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High Pressure Fuel Pump - this is a direct injection engine (similar to a Diesel, but it runs on gasoline and still has spark ignition) so instead of the injectors spraying into the head or intake runner behind the intake valve, it sprays directly into the combustion chamber. As a result the fuel system needs ludicrously high pressures to operate hence an engine driven mechanical fuel pump. Unfortunately BMW didn't get it quite right. The challenge is that Diesel fuel is pretty much kerosene so it has natural lubrication qualities; gasoline doesn't lubricate worth a crap so it's harder to design a HPFP and injectors for a DI gasoline engine than it is for a Diesel. Unfortunately the N54 was one of BMW's first efforts with this technology (I think the V12 came first) so it's got some teething problems.

Oddly if my memory serves correctly the old M-B 300SL "gullwing" used direct injection as well, but I don't recall anyone using it on any kind of scale since until the last 10-15 years or so.

Mods... well... all I'm running is a FMIC and a Cobb tune and honestly the car is fast enough that I need to exercise restraint to keep my license. It's not the fastest car out there but it certainly will get grudging respect from even your Ford and Chevy loving buddies