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my fuel pressure is going to 50 psi when i free rev the car.its a 96 gt with s-trim(8psi)36 lb inj,kirban regulator,255 intank,-trex,pro m 77.i had a 4.1 fmu and a paxton regulator but i remove the fmu and added the kirban boost sensitive regulator.the fuel pressure only increase by 1-2 psi when i rev the car with the paxton regulator.is this normal.if i go wot from idle it will hit 50 psi with 2 lbs boost and then the fuel pressure seems to hold at 50 gradually increase 1.1 up to 8psi..my base fp is sat to 40 with vacum attached.am i ok or should i decrease my base to 32-35 with vacum on.
 

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I'm not totally sure what you're saying, and if I did I doubt if I have a fix, since I don't do my own work.
However, I don't "free rev" my car much, but if I did, I don't think FP would rise more than 1-2 lbs under no load conditions. Mine is set at 39-40 lbs FP (before engine gets real hot) with vac line off. With vac line on, at that FP and idling, I see about 32 on my guage (a little less when engine get hot). When I accelerate under boost, I get at least a 1 LB FP increase for each 1 LB of boost, all the way up. You probably should allow for some differences in guages.
If yours is not doing that, and you are not getting that FP increase, I would be careful until you get it fixed. Good Luck.
 

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Have you checked your a/f ratio on the dyno? I'm running FMU-less as well, but I have a very healthy fuel system on the car. I wouldn't try it unless you've upgraded the lines and the fuel rails as well, which you did not mention. Mine will hold 52/53PSI at WOT without the FMU and the a/f is fine.
 

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Mine was right around 30-32 just like Ralph Greene and would increase 1psi of fuel pressure per 1 psi of boost with aeromotive fuel pressure regulator. I had the fuel pressure set at 40 psi as a base.
 

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I run 42lb inj with no FMU, 255 intank, 255 inline and run base FP without vacuum of 34psi. Car runs 11.2:1 to 11.8:1 air/fuel and see about 50-55psi at max boost. Hope that helps

Alain
 

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Silverstang...Are you sure you meant 34psi with out vacuum? I run the same fuel set up as you do. I see 34-35psi with vacuum connected and 42psi with vacuum disconnected. My A/F is 11:1 at max torque then leans out to 12:1 at 6800rpms. Not sure if fp will be different in a Cobra.

Jerome
 
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