Running too rich....

[LowdPypes]

I am not sure how this is possible with the factory fuel system and a supercharger but it's true, I'm running rich. I also think that this has something to do with why I get such ****ty gas mileage. Any suggestions?

 

[Alec]

Don't you have an aftermarket FMU? If that is piggybacked through your stock FPR you could have a bad FPR. It could also be your O2 sensors or cats going bad.

 

[Alec]

Oh one other thing, when I hooked up my ZEX box to my fuel vacuum lines it caused me to run really rich since it is meant for a stock fuel system and not mine. I just disconnected it and used my FMU to adjust the fuel.

 

[LowdPypes]

Upon installation of my blower, I did a little homework and I even talked to my buddy at Ford. Seems as though in 98, the fuel system was beefed up to 190lph or something like that and powerdyne said that the FMU was not necessary. Should I just disconnect the Zex pressure lines?

I have a A/F meter and it seems to be ok. constantly fluctuates under normal driving, goes to green when I nail it and red when I lay off. How would I check the FPR?

 

[Alec]

So how have you determined that you're running rich? Just the exhaust and mileage?

If it is recent then it wouldn't be the ZEX, that wouldn't occur suddenly. Hmmmmmm. You said your A/F looks normal......

I'm thinking.

 

[LowdPypes]

My mileage has always sucked??? 10-12mpg

 

[Alec]

well disco the ZEX vacuum lines and see what happens. Just remember not to use it during that time

 

[james t]

if your not running much boost, you can ditch the FMU, but you really need an adjustable FPR to do it. once you ditch the FMU, you bump up fuel pressure until you get it right. ideally, you would need a custom dyno-tune to do this, but if youre not over 8psi you could do it with an adjustable regulator and be ok.

 

[LowdPypes]

Tell me what I need to get and I will get it.... if it's an FPR that I need, then what type?

"If' I only had a brain... "

 

[james t]

LOL, any fuel pressure regulator for a 88-93 mustang will work. just get a good aftermarket one thats adjustable, and replace your stock non-adjustable one with it.

understand, im not 100% sure this is gonna work perfect, all im saying is it should work. the general idea is ditch the FMU, go to way bigger injectors, and use both the FPR and a computer tune to have the fuel ratio were you want it from idle to redline. i helped a friend do this without the comp. tune on his mustang, and it worked. but, he got bigger injectors and was running pretty low boost at the time.

with stock injectors, you may have to run the fuel pressure real high. if it doesnt work, hook the FMU back up and turn the pressure down. a good FPR is around $100, and you'll need this sooner or later anyway.

 

[james t]

i changed my mind... i see you are running 9psi... is that on the boost guage? if your running that much boost, you cant ditch the FMU without going to bigger injectors. 19 pounders are just not enough injector to run over 5-6psi with no FMU. sorry.

get the adjustable FPR, and LOWER your fuel pressure while keeping your FMU. its real easy to adjust, and here's what i would do...

check fuel pressure with the setup you have right now. order the adjustable FPR, and when you get it on, set it 2lbs. lower than what you have right now. drive it around, and lower the pressure in 2lb. increments until you get it were you want it. in other words, if you have 36psi right now with the key on, set it to 34psi and drive it. still not enough? go to 32... then to 30... until you have it dialed in. sorry for 2 hella-long posts in a row.

 

[LowdPypes]

not for the timid, huh.... well, I ain't scerred.... So, I am looking at these Aeromotive ones cause I beleive that is what we have on the mustang. Should I get the one from 35-80 or 30-70? Next question, what does dial in mean?

Sorry, I try.... lol

 

[james t]

get the one from 30-70.

"dialed in"- were you are somewhat stoich throughout the rpm range. in other words, play with it until you get it were you are not rich and not lean. you wont be able to have it dead on at every rpm, you just have to comprimise and get it were it is not rich or lean throughout most of the rpm band.

 

[LowdPypes]

It's now on my list of things to do once I get all this body work done...

Should I install a fuel pressure guage?

 

[james t]

wouldnt hurt.