Yes I know FMU's suck. Yes I searched for Vortec FMU and came up with a ton of matches, but did'nt find how to find the ratio. I got it second hand and want to know what ratio it came with, so I took it apart to get to the disc but there's not a damn thing printed on or in it, how do I know what ratio it is?

 

If you have access to a WB, id personally just rip on it and see if its supplying enough fuel. (adjust boost to suit, haha)

If you dont have a WB, maybe you have access to a fuel pressure gauge (preferably taped to the windshield) and can verify that your getting atleast 7-8 extra psi of fuel pressure per lb of boost. That would get you in the ballpark a/f wise for low psi setups on a stock fuel system. :1

 

There has got to be a way to identify the ratio with out actully measuring the fuel pressure to boost ratio. I will have a fuel pressure gauge on it when I start boosting to make sure it's working right, but if it is the wrong ratio, I want to know now so I can find the right one, instead of boosting the car than haveing it sit for a week while I wait for the right disc to arrive.

 

get a fuel pressure gauge. hook up the fmu. turn on the car now hit the fmu with pressurized air. now take the new fuel pressure - old fuel pressure / psi of the air you hit it with. this will give you the ratio

 

look at the bottom of the fmu there should be a part number ingrave on it that will tell witch one you have then go to vortec web site and match the part numbers hope that help you

 

Thanks that helps.
6Z110-114
It's an 8:1, good thing I know that now. But, if the disc was replaced I would'nt know.
Looks like that ratio will be a little too low for stock injectors.

 

10:1
40 psi stock plus 10:1 @5lbs boost =
90 psi fuel pressure, sounds good right??

 

Sounds good, but I dont know if an added 50psi of fuel pressure is enough to support 5lbs of boost. I have 19lb injectors.

 

it really depends on your turbo. throw it on and see if it leans out on top if it does than get a kit to change the ratio

 

You can order the discs from a Vortech dealer and they are cheap.Get a couple more and trial and error it.Doesnt take much to swap them around.