FMU

[shadowgames81]

If I put the fmu on w/ a 19# disc and I'm runnin 24# injectors will it mess something up or just not run to its full potential? How will I know if the wrong disc is in? Also if I get an adjustable fmu how do I know what it is set for?

[shadowgames81]

can I use a vortech recalibration kit in a paxton fmu?

[F=MA]

It'll just run huge fat, is all. Why don't you use an 8:1 disc for 24s? The Vortech ones and the Pax ones are interchangeable.

F=MA

[speedytang]

Adjuctable FMU still has Disc that you change to get to the best A/F ratio for your car.

[shadowgames81]

I have a paxton fmu and don't know what disc is in it. Thas why I was wondering about how it will run cuz if it has 19# disc I have 24# inj in it right now and don't wanna mess it up. So even if I get an adjustable on I'd have to buy more discs?

[speedytang]

Super FMU comes with all the disc and has other settings you can change to get a better tune. Go to Vortech web site and it has listed all the disc sizes and what Lb. they are for. You can even search this site it has been listed many times.

[jchalfan]

Ok, I'm running a red (10:1?) paxton FMU with my 24lb injectors... Is this the wrong one? Should I be running 8:1?

My kit was originally off a '93 cobra that had 24lb injectors, so I asumed I had the correct fmu...

Sorry to hijack the thread.

[shadowgames81]

when I looked online it showed a different disc for the 24# cobra injectors and i guess ho 24# injectors. Whats up w/ that??

[F=MA]

The guide to sizing FMUs on Vortech's sitte and others is a rough guide only and pretty safe. Your needs will be determined by your engine and the volume your fuel system can sustain under high pressure.

8 or 10 to 1 could be correct for 24s. You need to do a plug chop/dyno run on the safer 10 and see what's up. The 93 Cobra kit is on a richer tune not because of the injectors but because of the heads, cam and intake, plus the computer settings. The motor has higher specific output than the regular 5.0 on E7s.

F=MA

[shadowgames81]

so if I have a completely redone block w/ a holley systemaxII kit and anderson pms what size disc should I go w/ ??

[F=MA]

If you have the Anderson, you should junk the FMU, put 42 pound/hr injectors in and tune it in properly.

F=MA

[jchalfan]

Good info, thanks. I guess I'm better off with the safer 10:1, better safe than sorry. One of these years I'll get bigger injectors and a tweecer... Maybe.

[shadowgames81]

how bad will those make the gas mileage?? My car is already pretty bad on gas but I'd like to be able to cruise it on the streets still.

[F=MA]

Tuned correctly, the loss should be minimal. I find that, however, anything above 36s starts to have a detrimental effect on mileage, as it gets progressively more difficult to dial in idle and low speed fueling. You might lose a mpg or two going from 36s to 42s, even tuned in right, it's hard to say, as so many other factors affect mileage.

Honestly, if a stock displacement EFI 302 is bad on gas, something's wrong, either with your foot or the engine. These cars are really quite sippy for a 5.0 litre engine, especially on the highway. I have busted 30 mpg frequently on my 5.0, with 3.55s, on the freeway, and typically sit around the 18-20 around town. Now, that's on an Imperial gallon, which is slightly larger than your US gallon but, you can do the conversion if you want.

F=MA

[shadowgames81]

so what you think the 36's would be better?