i have both on my car.....
i am using a 8:1 disc in my fmu and at the same time i am using a fpr.... i want to know what psi the fuel pressure should be at...

 

i tried adjusting the fuel pressure with the fpr, but the fuel pressure wouldnt go down... would it be beceuse of the fmu???
thanks

 

I think it would be rather unlikely to be caused by the FMU; your fuel pressure should be changing regardless how you installed it, as long as it's running. I'd imagine the FMU would simply act as a multiplier for whatever you do with the FPR, or in reverse order... but I've never done anything fuel system related (aside from tinkering with my AFC), so I can't give you a certain answer

What kind of fuel pressure gauge are you running and how/where exactly was it installed? Maybe one of us here can help if we know more about the setup.

 

Actually, the FMU just keeps the fuel in the rail longer....

The pressure is actually regulated by the Fuel Pressure Regulator (FPR).... not the fmu...what fpr are you using?

 

im not sure what brand it is.....
but it should be working properly...
what if i take off the fpr and use the 8:1 fmu only?? would my car run lean??? cuz i dont have the extra fuel pump that came with the vortech on my car...

 

you wouldn't even start your car because you'd flood your motor. The FMU only controls fuel when there is no longer vacuum. So leave your fpr there... you should be at about 34 psi of fuel at idle, what are you at now?

If you don't have the extra fuel pump, you're running lean right now.... let me know if you need it, I have a spare laying around.

 

i am running way rich right now... fuel pressure is at 75... i tried turnng it down but it wouldnt go down... so i used my afc to lean it down at idle, but i am still very rich....

 

jesus.... 75 psi... SUPER RICH hehe...


yeah sounds like you're fpr is F#$@#!.

As of now, you may be better off running the oem fpr... at least then you won't be running so damn rich hehe... but it sounds like you're fpr is shot.

 

Why'd you keep the fmu in? I just left the cartech fpr in and removed my fmu... You can adjust idle and fuel pressure raise with it.

 

Because: He's got a Vortech FMU, I'm not familiar with how the cartech operates.

The FMU controls fuel while on boost by keeping more fuel in the fuel rail, but does not operate while NOT on boost.

The FPR is the only thing that controls fuel when OFF boost by maintaining the fuel pressure. The fpr alone CANNOT give the correct amount of fuel under boost.

 

The Cartech can.. It increases more fuel according to vacuum.. By turning the smaller **** you can increase fuel pressure. The more you boost the more fuel you get. That's how mines is setup..

 

mine....
idle : 39psi
full boost @ WOT : 112psi.

8:1 FMU and no FPR

 

it doesnt matter if the cartech is or not... he doesnt have one, hence the 8:1 disc.

 

FMU never affects idle pressue. it is activated when it receives pressure and it limits amount of fuel leaving the engine.

 

i am actually running fine now....
fuel pressure is still crazy... but i used my afc to turn it down at idle.....
so should i take out the fpr and use the fmu only????? or should i take out the fmu and use the fpr only and use the afc to give it more fuel during boost??

 

how much boost are u running?

say 8psi of boost with 8:1 disc...this is how you get the fuel pressure at 8psi.

8psi * 8 + idle pressure/2


are you saying you are running 75psi at WOT? if so, that sounds normal.

I dont think your car will run lean with an 8:1

and never take out the FMU.

 

Really? I took out the vortech FMU.. I'm just using the cartech fpr and everything works fine??

 

i am running 75 psi at idle...
that is the problem...
so should i just take out the fpr instead???
would my car run fine with the fmu only????
and i am not sure if i put the 8:1 disc in properly....
and i should be running 9 psi of boost...

 

!?!?



Then why do I have a Cartech FMU? It's not even hinted at being called a FPR in the documentation.

 

I would try to run it without the aftermarket FPR.
the FMU should affect idle fuel pressure. have you try to boost and see what kinda fuel pressure you are getting? just rev it up, dont run it

 

you need some sort of fpr... whether it's the oem nissan fpr or an aftermarket one running adjunct to the FMU. Why is this so complicated for everyone...?