Walbro 400lph Pump...what fuel pressure???

[1SloEvo]

First off, I want to say the 400lph walbro pump is an excellent pump for those looking to stay with a single pump and make a considerable amount of power over what a single 255lph pump can do. Installation was very easy in my FWD 1G. You need the filter specific for the pump to attach correctly. Otherwise, I dropped the pump in, used a stainless heavy duty worm clamp to hold it in place and everything else hooked up. I did have to put terminal ends on the wires to plug into the fuel pump, but if you buy the installation kit, it comes with a plug that will plug in.

Now onto the meat of why I wanted to write the thread. I am running a 14b turbo currently on 91 octane. My injectors are 865cc injectors. I replaced the stock fuel filter with a Trickflow inline filter with a stainless element that flows very well. And I started out using a stock FPR. The car ran rough at idle with constant up and down revving at idle and it would die when coming to a stop. I had a friend come up and help tune the car and everything worked great. Air fuel when cruising or under load was constant, stable and consistent. By narrowing down the issues, we came to the conclusion the pump was overrunning the stock regulator causing the idle issues. So I ordered up an AFPR kit. Installed it, set the base pressure at 37 psi (what I believe base 1g pressure is) and made a couple of pulls. Under boost, the car was going lean by approx. 1.2-1.3 points. So I raised the pressure to 43psi. Still lean by over half a point. At this point, I just worked on the fuel map and injector scaling and got it a little better.

Tonight, I wanted to figure out what the base pressure was on the stock FPR, this way I might be able to get the car running strong sooner. I made an adapter to hook up the fuel pressure gauge with the stock regulator. What it was showing was 50-51psi of base fuel pressure. So this pump is completely overrunning the stock regulator at idle. Now that I have it figured out, I will probably just set my base pressure at 50 psi for now so the tune should still be solid and work on adjusting it lower later on when I swap to E85/rage gas.

 

[bryanwheat]

Set it at 38 than adjust fuel maps. 50 is pretty high, the pump will flow better at the lower pressure.

 

[1SloEvo]

I will set it around 40psi when I go to E85 or race gas. Don't feel like having to retune the car all over when I just got that solid tune done less than two weeks ago.

 

[bryanwheat]

Injector flow patterns change at higher pressures also. There is a good video i watched a while back. As the pressure went higher some injectors actually stopped working. Your base fuel pressure is set to 50, but it will raise 1 psi of pressure for every psi of boost. If you are running 50 base and than 20 lbs of boost than your fuel pressure under boost is going to be 70 psi opposed to the 58 psi that it would be with the regulator set at 38.

 

[1SloEvo]

Yeah...I understand that as well. I was mainly putting the information out there for those interested in dropping in a 400lph pump on a stock regulator.

 

[nfernotalon]

I bought the 400 from you I believe. This thing is powerful it completely over runs the stock fpr my car won't even start. I have a fpr on the way.

Edit: I got it to work fine on my stock fpr it works perfect.