Rebuilding an FMU

[240RB1]

i am pieceing a turbo kit for my DD that will stay under a 300 dollar budget. only thing left is an fmu. i went to a local speed shop and the owner says he has a used one that he will sell me for 25 bucks. i would buy a new one but if i could rebuild a used name brand one i would learn and save a couple of bucks. he is selling a blue vortech fmu that supposed to work but does not know the ratio.so my question after all the jibber jabber is how do you rebuild an fmu? and how can you tell the ratio it is by looking at it? i want an 8:1

Sorry for the run ons....i will post a little build thread if people are interested.BTW this little build is on my newly aquired coupe.

[driftin_sr20det]

Its pretty straight forward, just disassemble and replace diaphram and calibration disc then reassemble. I will tell you though your probably better off with a 6:1 as opposed to the 8:1. My car was running way too rich with the 8:1 and I've seen a few other guys on here with the same issue that also say do the 6:1.

[neverlift]

<<<<has 7:1 and its rich as well.

you may not need a rebuild, there should be a serial number on the fmu and that will correspond to the disc that it came with from the factory. Mine was a 12:1 from a mustang kit.

My lower section was bad, take it apart and see if the metal disc(very thin and flimsy) is still good, if it is bad you will just over fuel, always.

IMHO buy the tuning kit, it has all the disc you would need to tune the system.

In most cases safety is important, I like being rich oil is cheap enough to change every 1500miles

[240RB1]

Ok thanks guys so you cand break it by opening it? i guess i will buy iy and look around for a "tuning kit".

[neverlift]

well you can break stuff taking it apart, but unlikely. You can really f*** the diaphragm(s) up on assembly, by over tightening.

chances are this is a 12:1 and the lower aluminum disc is shot(just like mine :p )its okay if the diaphragm is still good , you can make another one from a mtn dew can but it has to be mtn dew or it wont work. I could not justify the 50 bux vortech wanted for a small aluminum disc and silicone diaphragm. If the top is already 8:1 you should be good once the visual inspection is done. But if you have to buy the recall kit go ahead and get the tuning kit for a few bux more. best prices I found I think was superchargers online, fast cheap shipping

can I also advise you to spend a few hundy more for safety items? such as wideband a/f monitor,walbro hp pump,and 300zx filter, and if any fuel lines are suspected to be under rated swap them to something better goodyear makes decent rubber lines that have a sleeve in them, making them very strong.good luck man pull 3* if you live in warm weather or get s***ty 91octane , keep it under 8psi and long live the kat

[240RB1]

Sounds good. i will buy the fmu then shop around for the rebuild kit...as for parts i installed a z32 tt fuel filter a couple of days ago and tomorrow i will be buying a new 255 walbro pump from a friend so were set lol as far as the wideband goes- i will refrain from buying that because of my budget i will just retartd timing on the dizzy and hope for the best. i run only premium v-power so i hope it wont ping

[neverlift]

if you cant wait to get a wideband, dont boost it