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      09-26-2012, 10:10 PM   #26
ajm8127
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Drives: '07 335i
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So the high pressure pump has the capabilities to flow enough fuel, but its the lpfp that can't keep up? Is the hpfp able to just multiply what the lpfp can provide? In a turbo system with port injection, it is typical to get an adjustable pressure regulator and turn up the fuel pressure to allow more fuel volume through the injector in a fixed amount of time. So if you get a higher pressure lpfp in the n54, the hpfp will be able to take that excess pressure and multiply it, providing additional pressure to the injectors, or is the lpfp just not able to keep up with the volume demands? Are people hitting limits with respect to stock fuel pressure at the injector and injector pulse width (apparently they are)?

I guess what I am asking is what is the advantage to an upgraded lpfp? More pressure, more volume? How does this affect the hpfp and the volume of fuel through the injector in a fixed amount of time?

I'm not questioning the necessity of an upgraded lpfp, I'm just trying to learn about the limitations of the stock system.