in the ati procharger book it says the fmu will spike the fuel pressure up to around 75psi, question is i have a rail mounted liquid filled fuel pressure gauge that only goes up to 60psi what happens after that?

 

The FMU will defenitely bring the fuel pressure to 75psi, as long as your pump can supply that much pressure. My TT IROC has fuel pressures around 80psi at 6psi of boost. As far as the gauge, the high fuel pressures could slightly effect it's accuracy, but it shouldn't give any other problems. I would highly suggest a remote gauge that you can tape to your windshield for testing purposes. You want to make sure that the fuel pressure doe not fall off under sustained high engine loads. If it does, you need a fuel pump upgrade. Once the pump has been proven adequate, then you can remove the gauge. An electric fuel pressure gauge mounted in the car may be an even better idea.

 

I use the Autometer 2-1/16" electric in my car. What was sweet is when I bought mine there was a recall on the guage slightly afterward and Autometer / Summit gave me the $200 jobby instead of my $60 dollar Autometer. I have an Earl's 90 degree where my shrader valve was and hooked up my guage sending unit. The guage goes up to 100 PSI. The down side is theres now a fitting and sending unit about a foot away from a heat source (the header!). If anything lets loose I could have one helluva fire on my hands. Oh well, I trust Earls parts.

 

if you're asking what will happen to your guage... well it will get pegged. In theory it can damage the guage, in practice it probably won't.

As far as 75psi, that depends on boost and ratio, there are FMU setups that go over 100psi under boost.

 

My suggestion would be take it out, sell it to someone who is going to be using nitrous or someone who wont have as much fuel pressure. Then by yourself a better one with a higher reading.

 

thanks guys got an electric 2 1/16 gauge to 100lbs to mount in the car.