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Has anyone with a GSR and a Walbro pump been able to lower the fuel pressure below 47psi?
I just removed the OE regulator from my car and ran a hose from the fuel rail to a can. Running the fuel pump with no regulator the pressure was under 20psi. Then I put the OE regulator in place and ran the outlet through the hose to the can. Running the fuel pump with just the OE regulator yielded a 50psi reading at 20" vaccuum and 47psi at 25" of vaccuum (I used a hand vaccuum pump).
This contrasts with the readings when using a stock pump where the pressure is 43psi at 20" (probably lower at 25" vac, but didn't check).
It sure looks like the OE regulator is a significant restriction. Perhaps the Walbro's much higher fuel volume results in a higher minimum pressure and a higher pressure range from 20" down to 0" vaccuum.
Anyhow, I can see 2 obvious solutions here:
1) Replace the OE regulater with one that is less restrictive.
2) Replace the fuel pump with one that moves a lower volume of fuel at lower pressures. Does anyone know the flow ratings of the Bosche pumps?
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JRCivic is on the "lower volume" pump as we speek. He should how is works sometime this week I would think. This is the last thing I am waiting on until I do my injectors, rail, adjustable regular (which may not even be need of the pump works out) Cartech, and the pump.
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98 GS-scR w/ 8psi JRSC, Walbro HO fuel pump, AEM cai, Airmass header, Thermal Exhaust, Skunk Works cam gears, J&S safeguard, Ground Controls and KYB AGX's, and of course to slow down, KVR X-drill F&R rotors and Carbon Kevlar pads and V1 to signal the slowing down and soon to go on a Carbon Fiber diet,RC 310 steriods,and new sticky foot wear of the 555R type
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I may have solved this problem. I've installed a bypass which routes a small amount of fuel around the OE regulator. One end of the bypass is tapped into the adaptor between the fuel rail and the OE regulator and the other end is teed into the fuel line which runs between the OE regulator and the boost sensitive FPR. With this arrangement, only the NA fuel pressure is lowered. The fuel pressure when boost is present is controlled by the boost sensitive FPR just as before. My car's NA fuel pressure is now in the stock range.
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I've been able to bring down the idle fuel pressure to around 33-35psi, but as soon as vacuum is gone it goes right up to 70psi w/ the stock JR FPR, but I think I have a fuel leak so these findings maybe nill.
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What fuel pump are you using?
