FMU question?

97stanger · Mar 31, 2007

Hey guys,

I just got my car back about a week and a half ago from putting my SQ trim mongoose kit on. The shop gave me back a box with a bunch of unused/old parts. I happened to notice that i have a brand new Vortech FMU setup sitting in the box unopened (until i opened it). I was just curious as to why the shop didnt install this? I used a Walbro 255lph intank fuel pump, and not the T-rex if that makes a difference?? Any thoughts please?
Oh, and i also don't have a fuel pressure regulator either...

94twinscrew · Mar 31, 2007

Well,the fmu that came with the kit could have been a 8:1 or 10:1 ratio,which combined with the 255lph would have put your fuel pressure above 80psi or higher depending on boost level.(which makes it a PITA to tune) Most tuners like to just rely on base static pressures for ease of drivability,and max optimal injector performance when running larger injectors....so there is no need for an adj regulator. Especially when our regulators are a true 1:1 ratio,which means for every pound of boost,you will see an extra 1psi of fuel pressure. So with stock pressure at idle being 30-35psi,and out of vaccum being 40psi.....at 10 psi of boost,you will see 50psi of adjusted fuel pressure. Consider it a mini FMU.lol Adj regulators are pretty useless now a days,especially when fuel flow can be controlled by a tune,the same can be said about FMU's....they're more of a bandaid than a needed part.

97stanger · Mar 31, 2007

wow, some very informative info there. Thanks! Maybe now i can sell this for a little extra mulah. Its a pretty expensive piece! Or do you think i should hang onto it in case my tuner was to ever need it with future mods?

94twinscrew · Mar 31, 2007

You won't get much for it even though it's new.....there's so many used ones for sale on ebay all the time,you might as well keep it in case you get in a pinch. Like when you max out your injectors,and can't afford the swap....you can use a recalibration kit on the fmu to make it a 4:1,and gain a little head room. I ended up having to do that with my combo,I just don't feel like going to 50's.