I'm getting my fuel system ready for power adder, but now i'm a little confused about FMU. At first i want to use the stock injectors, until i can afford maybe TwEECer or PMS. I found rail mount BBK, Aeromotive and Mallory adjustable fuel pressure regulators that have boost/vac rise ratio 1:1. So those will rise fuel pressure with boost, but is it enough, or is there still need for a FMU when using one of those AFPRs?
FMU or AFPR?
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fiveohwblow
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- Jul 21, 2005
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An FMU will run ratios such as 8:1 or 6:1 thus generating much more fuel pressure than 1:1. Anyone will recommend an AFPR with larger injectors. An FMU is just a band aid really for someone who does not have money for a tune, larger injectors etc...
As for the brand, I would recommend Accufab.
Hope this helps!
millhouse
Founding Member
What kind of power adder…and what is your combo?
The stock fuel pressure regulator has a 1:1 ratio from the factory, so unless you have some existing issues with it….there is no need to pick up an adjustable unit yet. If you feel the urge to buy one regardless….I've had good luck with my Kirban.
I'd also strongly advise against getting a FMU. It sounds like you would be taking a shot in the dark with picking the proper ratio….and with no way for you to measure AFR's, you are asking for trouble.
The stock fuel pressure regulator has a 1:1 ratio from the factory, so unless you have some existing issues with it….there is no need to pick up an adjustable unit yet. If you feel the urge to buy one regardless….I've had good luck with my Kirban.
I'd also strongly advise against getting a FMU. It sounds like you would be taking a shot in the dark with picking the proper ratio….and with no way for you to measure AFR's, you are asking for trouble.
PUNISHER RACING
Active Member
If you are running your stock 19's I hate to say it but use the FMU, ideally you should ditch it and run 30's with a 190/255 and an AFPR
I have Eaton M90. Car is basically stock, just ported e7 heads and BBK shortys + o/r h-pipe. Stock injectors, 255lph intank. It's true budget build, as i don't have much money to spend on it. I will get TwEECer or somethin, but not now. I was thinking to swich to bigger injectors at that point. I know what everybody thinks about FMU, that is why i asked if i could do without it.
I didn't know that stock FPR adds fuel pressure with boost. I thought that it was only those i mentioned that did, because on Summit store theres nothing said about boost on other regulators.
So FMU is a must with my setup? 1:1 ratio is not enough? I am going to run probably less than 6 psi now, depending on what size pulleys i find.
I didn't know that stock FPR adds fuel pressure with boost. I thought that it was only those i mentioned that did, because on Summit store theres nothing said about boost on other regulators.
So FMU is a must with my setup? 1:1 ratio is not enough? I am going to run probably less than 6 psi now, depending on what size pulleys i find.
millhouse
Founding Member
Most actually are. They have a 1:1 rising rate which means for every lb of boost the AFPR diaphragm sees, the fuel pressure will go up 1psi accordingly. FMU's on the other hand have a higher ratio than 1:1.
They push your injectors far…far past maximum duty cycle which cause irregular spray patterns or worse, damage or failure. The tend to be somewhat reliable for a while….but I would not trust what they'll do to the rest of the system for long term use. They are not to be substituted for a good tune either. Simply throwing on an FMU does not mean your entire WOT AFR's are going to be safe. What you will typically see is some areas that are lean…and others that are very fat. The only way to get everything in between to come out right is with a tune….in which case you might as well just upgrade the injectors and MAF.
millhouse
Founding Member
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