I plan on running the Walbro 255lph pump to 440cc injectors. Do I need to change out the FPR and order a rising rate regulator? Or will it work fine with the stock regulator? I have read other posts about fuel pressure being really high at idle(75psi) and dropping to redline(50psi). What are the drawbacks/implications of this setup? Is it even possible to put a rising rate FPR without a return system? I know the best route would be the CJM or AAM return systems, but I want to make sure that it is really necassary for my application. I am running 7-8 PSI and I do not plan on changing my boost levels.

 

The AAM return system comes with a FPR . With a rising rate of 1 to1 . You will not have any problems getting fuel at what ever boost you run . Well ....any boost level you could get to with a SC

 

Moved. Please post in the appropriate forum.

 

I ran with a Walbro 255, no FPR, and the 440 injectors for a few months. The car would still start to run lean after about 8psi, and it was impossible to tune due to rapidly dropping fuel pressure as boost and RPM would rise.

You can run a rising rate FPR without a return system, by install an Aeromotive 1:1 FPR above the fuel pump assembly, and just "returning" the fuel directly back to the tank. But becuase fuel pressure is being set at the tank, instead of the fuel rail, there may be some issues with that. Also, the stock fuel rails have a single feed, and then they have one tiny bridge filling the other side of the rail. Also remember that the stock FPR is a POS that will wreak havoc with your fuel pressure unless you replace it with a plug, and siphoning kit.

I guess what I am saying is that there are some others ways to run that FPR, but none of them are ideal, and they present their own problems. If you want accurate, and rising fuel pressure AT THE RAIL as boost increases, the only viable option is the full return system, rising rate FPR, stock FPR plug..etc..etc..

 

I have read about needing spacers. Are they a special spacer or are they washers? Do I need longer bolts? Where do I get the bolts and spacers if they are a special type?

 

I wonder how well a return fuel system would run if you did the Walbro fuel pump, rising fpr at the rail, siphon correction kit, WITHOUT rails? It seems as if the rails are not cheap and unfortunately, I don't have a $1K to drop on the complete kit.

 

badmonkey... you should be fine without a return system. the problem with high pressure at idle when putting in a 255lph is because the factory intank return system is too restrictive to flow enough to keep pressure where it should be.

you SHOULD be able to fix the problem by oversizing the swirl jet at the bottom of the fuel canister. It is the yellow part at the bottom and it snaps out by pulling it downward. Oversize the restriction oriface to about .070 and that should probably get you where you need to be at idle.

-Charles
CJM

 

Charles,
I will be installing the Walbro the wek after next and enlarge the swirl jet. Will my FPR be sufficient while under boost? I plan on removing the aux fuel pump and Procharger's FMU and get my ECU reflashed, again. Thanks.

 

well your fuel pressure will not climb up with boost using the stock regulator, so you will be capped off around 400-410rwhp with the 440s using stock regulator with a 255 lph pump.

 

I plan on installing my Walbro this weekend. Will my FMU need to be re-tuned prior to my injector install? Will it be OK to drive for a week? I just want to install the fuel pump first and the injectors next weekend. I will have my ECU reflashed after the injectors are installed.

 

It will need to be tuned after the injector and fuel system upgrades. Becuase your fuel pressure mapping will be completely different than stock, the maps will need to be retuned.

Charles, how is this person going to control his fuel pressure without a dedicated FPR? I know the Walbro and siphoning kit will help, but the fuel pressure will be hit or miss at best...and not rising with boost.

I guess it would work to 400whp...or close.

 

I know the maps will be off with the injectors, but will they be off with only the pump? Will the walbro, in conjunction with the aux fuel pump and FMU work in the interim, until I can get the injectors in and re-flash the ECU?

I don't plan on increasing the boost on my Procharger, I am still at 7-8 PSI. I would be happy with 400WHP, if that is what the fuel system will limit me to. If, in the future I want to increase power, I will have to go with the return system.

 

The car will run rich..but probably drivable.