FMU question

[Cavalier9696]

Currently IM running a 12:1 FMU and feel like IM not getting the boost I should. I have been talking to another DSM owner on here and he also thinks it could be a fuel problem. The pressure from this FMU is so hard that IM leaking fuel even with 2 hose clamps (like a drop ever minute or so). I have an aftermarket FPR but was told that I wouldn't need it. The FMU is currently installed on the drivers side firewall. I have been reasearching to make sure I can mount the FMU on the firewall for a 95 rs. So now IM thinking is there an FMU made for running low boost as in 5psi?

My meter says IM running rich when getting on the gas and lean when I let off. In idle it runs between neutral and rich.
Thanks.

[Cavalier9696]

Any1?

[david-b]

Originally Posted by Cavalier9696

Currently IM running a 12:1 FMU and feel like IM not getting the boost I should. I have been talking to another DSM owner on here and he also thinks it could be a fuel problem. The pressure from this FMU is so hard that IM leaking fuel even with 2 hose clamps (like a drop ever minute or so). I have an aftermarket FPR but was told that I wouldn't need it. The FMU is currently installed on the drivers side firewall. I have been reasearching to make sure I can mount the FMU on the firewall for a 95 rs. So now IM thinking is there an FMU made for running low boost as in 5psi?

My meter says IM running rich when getting on the gas and lean when I let off. In idle it runs between neutral and rich.
Thanks.

Are you seriously driving the car with a fuel leak still? Dude... no. If you don't know how to get the fuel from stop leaking, take it to a shop. Or learn how to use stainless steel lines/fittings and replace what you need to with those. Fuel is not something you let leak... ever! One drop a minute to one drop every day is not acceptable, no matter what.

A 12:1 FMU is making your fuel pressure high. If base fuel pressure @ idle is 47psi, you're raising 12psi for every pound of boost. Example:

1lb boost = 59psi FP, 2lb boost = 71psi FP, 3lb boost = 83psi FP...

Long story short, your fuel pressure is going to get super high in boost. You should be able to use the FPR to lower the base fuel pressure to about 23-30psi @ idle. People run this setup all the time though. I did it for about a year. 12:1 FMU, no FPR, 8lb wastegate... its a simple and basic setup which does good. Been proven to do good.

Do you have a fuel pressure gauge? If so, what is your FP @ idle?

FMU is fine on the firewall.

Car will always get lean when you let off the gas. The ECU cuts fuel as the motor is winding down, then turns it back on when it sees the right conditions. A 12:1 FMU will pretty much always make the car run rich until you get the FP down. That's why the 12:1 is a good starting point, since it's nearly impossible to run super lean and damage your motor.

[Cavalier9696]

I haven't been driving it. I have been driving my truck. I noticed the leak when I moved the car the other day to mow the lawn. I have an after market FPR but when I was getting the turbo installed you said I didn't need it. I have to get another one though cause the gauge is so foggy I can't see the psi on it. The leak in coming from the FMU itself from the hosebarb on the tank line. I have stainless steel lines and fittings. Without turning the pressure down it's going to leak. When I had the FPR on it, the gas flowed fine. But like I said, I was told I didn't need it so I took it off. So basicly when I put the FPR on I will be fine.

[SilvrEclipse]

Dave, you cant lower the base fuel pressure IF you are using stock injectors. It will f up your fuel trims. You should probably get an actually fuel pressure gauge you can put in the cabin so you can monitor it will driving. When you says your meter says your running rich is that a crappy narrow band gauge or do you have a real wideband o2 sensor. You will need a real WB bc the narrow band doesn't tell you shit.

[david-b]

Originally Posted by SilvrEclipse

Dave, you can lower the base fuel pressure IF you are using stock injectors. It will f up your fuel trims.

Jason, do you mean can't? I'm pretty sure he's using stock FIs.


Pull off the barb and wrap teflon to the threads. Then tighten good.

[SilvrEclipse]

Fixed.. yes I meant can't.