From what I understand if I upgrade the fuel pump my car is going to run rich right?? I've also seen where it will run rich except under boost unless the stock pump wasn't flowing efficiently, is this correct?? I'm just want to make sure so I know how much time I will need to retune the fuel map, because if it is going to take a while I may wait until I have a free weekend to do it.

Also once I get the pump changed and make sure everything is ok, I plan on upgrading to 4x850s. Is it going to run rich under boost initially or am I going to need to add some fuel and adjust back down?? I know I will need to adjust the idle and cruise. If I can't get idle to lean out enough by just adjusting the maps, do I have to do the recalc on the datalogit to tune lean it out??

 

If the same FP regulator is used, the only difference maybe richer on high boost and rpms unless the pump is sooooo strong it overpowers the FPR.

Do a FP pressure check before and after the install at idle and at the same boost level. this will directly answer you question.

 

I plan on keeping the stock regulator. I'll try the fuel pressure check if I get a chance if not I guess I'll just check the AFR's afterwards.

I'm assuming the 850s will also run super rich initially under high boost like they do under vaccum??

 

the pump will only increase volume. as stated if using the same fuel pressure regulator you might see a small difference if any. putting the 850's in will make you run richer. you shouldnt need to take any fuel out till the 850's go in. from what i've been told the 850's are a little difficult to control at idle. someone experienced should have no problem.