Can anyone tell me if there is a fuel pressure regulator that can turn the pressure down on the feed side. I was experimenting yesterday with my fuel injector cleaner conneted to the fuel rail. Instead of running the cleaner solution, I filled the canister with 93 octane and I set the pressure at 32psi which made my engine very responsive and it took away the rough idle Ive had all along with the stock pump and regulator. Theres a problem somewhere in the flow but I cant pinpoint it and this is all I have been able to come up with. Any help or suggestions are greatly appreciated.

 

Most aftermarket fuel pressure regulators will let you turn it down some probably to 32, but I can tell you this much running 32 psi will cause some burnt pistons, probably the first time you get in it.

 

Before you mess anything else up you need to develop a basic understanding of how it all works.

 

Can you expand on that anymore? Obviously I wouldnt be seeking help if I knew the answer all along.

 

Responsive at idle does not mean anything is better, if all else is good then you would run terribly lean under load lowering the pressure like that and engine damage would be likely.

The regulator does not actually vary pressure, yes I said that right. What it does is maintains a steady pressure differential between the manifold vacuum and the fuel rail otherwise under high vacuum the injectors would act larger due to spraying into a low pressure area. The injector sizing is a programmed input in the pcm used to calculate fueling, change the input pressure and you basically change the injector size and the computer can not make proper fueling calculations. When we test fuel pressure it appears to raise and lower because we are comparing to atmospheric conditions rather than manifold vacuum.

Last week my wagon started running bad but only at idle in gear stalling it up on the brakes smoothed it. My wagon has 223K on it and basically stock. A low flueling problem would present worse under load and RPM as would a spark problem. I did not want to spend the money on testing but I got to thinking it might just be a dripping injector causing a severe rich at low rpm/load, I had a spare set of low milage injectors I swapped in and it fixed the problem which without real testing seems to mean it was the injectors.

Had the car had headers on it I would have used an infared non-contact thermometer, looked for a cold tube and swapped that injector to another position to see if the problem followed the injector. I know that is big and long but hopefully I "taught a man to fish" with it instead of just handing him one.

What all is done to your car?
When asking questions it is VERY helpful to potential helpers if you have a vehicle and mod list for us to look at.

 

I always thought that a regulator was kind of like a restriction on the return side of the fuel rail. When it has lots of vaccum, like at idle, the diapham is holding open the valve in the regulator to let more fuel back into the tank. As the vaccum decreases the diaphram has a spring which closes the valve, more or less based on the amount of vaccum, to supply more fuel pressure to the rails. With an adjustable FPR all your doing is adjusting the tension on that spring. But, what ultimatley controls the FPR is throttle postition, injector pulse width, valve timing and igntion timing, because they are what control the amount of vaccum. Please correst me if i'm wrong, this is just how I understand how it works.

 

Well, Ya'll are both sort of right. the regulator is there to ensure fuel volume. it does have a diaphram and spring inside that responds to engine vacuum. but it is opposite of what you said mullet, at idle engine vacuum is lower so the regulator allows more fuel volume to return to the tank, then as you get into it and the engine revs up the engine vacuum becomes greater and the regulator responds to this by not allowing as much fuel volume to return to the tank. as caprice said it does attempt to keep a steady psi to the engine by controling this flow of volume, it will fluctuate slightly. But as he said a better idle with lower fuel pressure is not necesarily a good thing. I am curious to know some more info. hook a guage to your fuel pressure regulator see what readings you are getting while cranking, at idle, at 1500, and see if it holds that pressure with the key off, and for how long it holds it, do that and let us know what you come up with.