I was driving my car this weekend and noticed that the fuel pressure was between 33-34 psi. At W.O.T it goes up 2-3 psi.
Is this normal or do i have a problem. I have a stock fuel pressure regulator and no FMU, but 36lbs injectors and Program. It run kinda rich and loads to much fuel in to the motor when w.o.t is applied in the upper rpms.

Any advise on this will be greatly appreicated.
NiteRyda.

 

Why are your running no FMU? At idle my car is set a 40 psi. Whenever you hit boost your fp should go up 1 psi per lb boost.

 

Yea thats not right, your fuel pressure is dropping off. You shouldnt need a fmu as long as you have enough injector. Plenty of people are running setups w/ out an fmu. But I would have your fpr checked or better yet replaced.

 

Keep in mind that in a certain sense, the stock FPR IS an FMU. It is vacuum referenced, so the pressure should vary 1:1 with manifold pressure. You should see an increase in FP of 1lb per lb of boost. If not, you have a bad pump, clogged fuel filter, bad FPR, or a bad gauge.

Rich Krause

 

Yeah I understand but most of the time people usually go with 42 lb injectors to ditch the FMU. I did not know if 36lbers were adequate.

 

I guess it depends on what kind of power hes putting down weather o rnot he needs an fmu or not. But I totally agree with you.

 

I was hoping not to use an fmu either. I should be around 470-480rwhp with 6psi. I bought Accel 48lb/hr injectors. I dont need an impedence inverter (or is it converter?) do I?

 

You only need it when you decide to run a low impedance injector. Currently the biggest high impedance injector available is through Siemans (57 lbers). With 48 lbers you should be ok.

 

Cool. Thanks.

 

I am running 45psi at idle and am climbing up to 80psi @12# boost at 5300rpm. This is with an FMU and 100psi adjustable regulator and was done on a dyno. My fuel pressure does climb about 1psi per pound of boost up to 5# and at 6# it pulls strong to 80psi (its not linear). After I tuned it on the dyno, I checked my psi numbers with ATI and the agreed this is where it should be running. Incidently, the stock regulators are generally good to about 60psi, after that you can blow the seals.

 

I'm running 36# SVO injectors, no FMU, custom programming, fuel pressure (AFPR) at 52 psi @ 10 psi boost and dyno'd 527 rwhp at 5,800 rpm with a 12.0 A/F ratio. I would recommend 42# injectors but my results show it can be done with 36#. Fuel is supplied by a Walbro 255 lph HD with stock lines.