Fuel Management Units

**ASCOTTB35** · 09-26-2006, 12:19 PM

Does Anybody Know What Size Fmu I Should Use For A P6oob Procharger On A Sbc W/ 8 Lbs Of Boost, I've Heard Any Where From A 4:1 To A 16:1 And Now I Really Dont Know Wich One Is Best.

**Packy** · 09-27-2006, 03:29 AM

I don't know I don't use my FMU.

**EviLt4** · 09-28-2006, 04:56 AM

I dont run a FMU either. If you get one, just make sure its adjustable. You can find em on ebay all day long for $100. If you get a good tune on your car you wont need a FMU at all.

**ASCOTTB35** · 09-28-2006, 05:05 AM

Cool, Thanx For The Advice Guys!

**Mitch83** · 09-28-2006, 08:22 AM

I just wanted to second on what evilLT4 said. If you are able to tune your car you wont need the FMU. It's basically a rising rate fuel pressure regulator. As boost increases so does the fuel pressure. So if you get it tuned your fuel trims will automatically supply the fuel needed so a FMU wont be needed. I think they are a waste of money IMO.

**ASCOTTB35** · 09-28-2006, 08:43 AM

Yeah, That Sounds Like The Same Thing Other People Are Tellin Me, Thanx Again 4 Tha Info!

**ASCOTTB35** · 09-28-2006, 09:08 AM

What Size Injectors Are You Guys Runnin? I Have 29# Inj. On The Edelbrock Proflo Mpfi, I Hear Tha System Is Good Upto 550 H.p. But I'm Still Wonderin If I Need Bigger Ones Or Not (instead Of Mfu)?

**Mitch83** · 09-28-2006, 09:44 AM

I'm not sure if the chart is accurat or not but if I'm not mistaken 28# injectors are good for 407hp and 30# are good for 436hp this is crank hp. For 550hp you would need about a 38# injector.

**ASCOTTB35** · 09-28-2006, 10:24 AM

I've Talked To Other People Running The Same Mpfi System W/29# Inj. That Say They Are Getting 480 To 500+ Rwhp & If I Wanna Go Over That Then I'll Hafta Change Inj. & I Dont Know About "the Chart" Your Using, Wich Chart Is That Anyway?

**Mitch83** · 09-29-2006, 07:43 AM

cool, if they are hitting that then obviously the numbers on "the chart" are off. Now "the chart" i'm using is for turbo cars so it may be a bit diffrent.

http://www.turbonation.com/injector.htm

Here is a conversion tool that says the same thing
http://www.injector.com/injectorselection.php

http://www.moddedmustangs.com/perfor...culators/#disp
another as well.

All of these charts/calculators are looking like if you want to touch 500whp your gonna need 30+# injectors now that also depends on what duty cycle your willing to run. 80% is the highest recommened by most tuners to run safely. The stock injectors (29#) are good for 390hp at 80% duty cycle which is the industry standard if your willing to exceed that and run 100% duty cycle then you can hit about 475hp. It's up to you what you want to do and how far you are willing to push the limits of your stock fuel system.

I'm only quoting the formula's alot of times people get away with disproving what is known to be true so. Hopefully others will chime in with there personal expreince on the subject.