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desolate · 10-20-2009

Many guys run fast on the stock regulator with an upgraded fuel pump, but that isn't to say you should do it if you still want the normal operation of the way the system was designed. It was designed to change fuel pressure according to vaccum & boost. The stock regulator's return hole is pretty small, so fuel pump upgrades usually overrun them.

How people run fast without fprs is because, the operation of fuel regulation always rises above the overran amount @ wot, so under boost the stock fpr will not affect performance. The running rich and the like happens typically under 15psi of boost because 255 walbros usually overrun fuel pressures to around 55psi @ idle.

That's pretty high, however, in the real world it's pretty common for the car to behave normally. You might see a dip in mpg, but things won't be terrible. One of the main reasons why the car usually shows no ill effects is because the ecu can adjust and compensate fuel delivery off boost and such is by using the fuel trims. However, overall it's usually best to have the car work the way it was designed by upgrading the fpr.

10-20-2009	#17
desolate 91 TSi AWD Join Date: Oct 2003 Location: St. Paul, MN Drives: red 91 TSi AWD auto Posts: 348	Re: Injectors/FPR/Fuel Questions Many guys run fast on the stock regulator with an upgraded fuel pump, but that isn't to say you should do it if you still want the normal operation of the way the system was designed. It was designed to change fuel pressure according to vaccum & boost. The stock regulator's return hole is pretty small, so fuel pump upgrades usually overrun them. How people run fast without fprs is because, the operation of fuel regulation always rises above the overran amount @ wot, so under boost the stock fpr will not affect performance. The running rich and the like happens typically under 15psi of boost because 255 walbros usually overrun fuel pressures to around 55psi @ idle. That's pretty high, however, in the real world it's pretty common for the car to behave normally. You might see a dip in mpg, but things won't be terrible. One of the main reasons why the car usually shows no ill effects is because the ecu can adjust and compensate fuel delivery off boost and such is by using the fuel trims. However, overall it's usually best to have the car work the way it was designed by upgrading the fpr. Last edited by desolate; 10-20-2009 at 02:05 AM..