Fuel Pressure Issue With Corvette Filter/Regulator

[HATEHPTUNERS]

I've been attempting to tune a truck that has a Corvette fuel filter/regulator on it. I have an intermittent issue idling. Sometimes it idles great, other times it just falls on it's face and struggles faltering to find a good idle again. Driveability is great-and the VE table and MAF table are both +/-3% all across the graph. HOWEVER, this idle issue persists... 1 in 5 red lights you will be sitting there and can hear the engine begin to stumble and then the rpm's jump as the PCM adds timing to bring the idle speed up. I was logging yesterday and saw that when the engine dropped into the 400 RPM column on the VE table graph, the PCM was calling for pulling -38% of fuel.

With that in mind, I put a fuel pressure gauge on it... At idle the pressure is 63-65 psi... As soon as you step on the gas it drops down and holds tightly at 56-58 and will stay there until you let off the gas... When you let off the gas it goes almost to 70PSI for a split second, and then drops quickly back down to 63-65... I'm almost 100% certain this is the idle issue that I can't tune out... it's a mechanical problem so it CANNOT be tuned out.

Has anyone else witnessed this before? Should I just dump the Corvette filter/regulator and go to an after-market vacuum referenced regulator with return? If this is the recommended path, can anyone suggest a good regulator that I can buy? I just want something I can set up correctly one time, and then not have to worry about it.

For those that want to know what fuel pump... Since this is an LS swap project, we purchased and installed a "high performance" Bosch in-tank pump. The specifications say it can flow up to 100PSI... I think the pump might be over powering the filter/regulator at idle and that's the idle issue.

Any and all input is appreciated.

[gtstorey]

Not exactly an independent source, but it has been brought up on here before with other sources.
https://aeromotiveinc.com/aeromotive...gulator-combo/

[Lxjoshxl]

Someone I noticed with that style setup Had some issues he said. I Just Used an aeromotive FPR Return Style with My TBSS Intake and it seemed to work good. Only issue was the first regulator I got was Junk. P/N Is 13129

[blindsquirrel]

It's not the pump pressure, it's volume. The return path inside the filter can't flow enough back into the tank, and so it has nowhere to go but to raise the rail pressure. At idle or KOEO the engine eats very little or none of the pump's volume so ALL of it has to go back to the tank. It can't, so pressure rises above the spring's set point. As the engine eats more of the pump output less needs to be returned, so the rail pressure falls. Your pump is right on the borderline of that point where the return can't flow enough.

With even bigger pumps (or cheaper aftermarket filters with worse return flow) pressure can spike so high it actually locks the injectors closed and you get a no-start.

[HATEHPTUNERS]

Thanks for the feed back everyone. I've done some more testing.. Since it was idling okay, and holding good pressure for street driving using the factory narrow bands and STFT's, I put the NGK wide band in it to do some higher RPM tuning... It's either losing volume or pressure above 3500 RPM.. The PCM is calling for more fuel as the RPM's increase... The VE table would be in the mid 100's if I believed what my error graph was showing... average injector pulse width was 12.5MS @ 100% TPS, and the wide band was showing 14.62 actual while the commanded was 12.75 Could this be the Corvette fuel filter causing the issue? I'm wondering if I've got a pump issue as well.. The only way to know for sure would be to put the new vac ref FPR in place, install a standard fuel filter where the Corvette regulator is, and then do more high rpm testing to see if the pump can keep up. Under full throttle you can feel the truck being held back and the wide band confirms it.

[blindsquirrel]

Specifics would require a tune file & log to look at.