Fuel Pressure Questions

[Hognose]

I have a Kenne Bell adj Fuel Pressure regulator. I notice that after I turn it down to get my o2's in check, the FP creeps up over after a day or two.

There is a noticeable differnce in the way my car pulls when I get my 02's into the high 700's. But ir doesn't take long before they are back into the mid to high 800's.

Plus the I can't get it anylower than about 37lbs. If I put it to 36 I get a code 45 at idle and my 02's are very high at idle. I think that 36lbs would be perfect for the 14lbs of boost I am running on pump gas on the street.

My questions are could my regulator be going bad? And is there anyway around the code 45 issue with low FP? Thanks
Matthew

 

[redhotrod]

Are you adjusting the regulator with the car running and the vacuum line off the regulator, it should then be set to ~42lbs

 

[turbosam6]

Originally posted by redhotrod
Are you adjusting the regulator with the car running and the vacuum line off the regulator, it should then be set to ~42lbs

Just curious where you came up with 42 lbs.? He should set it wherever it works for him. Everyones car is different.

 

[denn454]

sorry fro trying to hyjack your thread but i have a very similar question and don't see any reason to have 2 fule pressure threads at the same time...

first off why do you disconnect the vaccume line when setting the fuel pressure? i always leave mine connected.
next thing is i was getting some knock before with the car running really rich, now that i have leaned it down it not only runs a lot better, but i get little if any knock. isn't that backwards?

 

[Hognose]

Yes I am setting it with the line off. I am curious also if I runn 100 and turn up my boost, should I turn up the FP also?

Thanks,
Matthew

 

[83ttypecooled]

regulator

Is your regulator leaking? Everything seems backwards in your description, and the vacuum hose could be sucking fuel directly.

 

[UNGN]

36-37 lbs of fuel pressure line off is low. Your fuel pressure at idle would be in the 20's. If the fuel pressure is changing line off, it sounds like the FPR is bad.

Are you sure the chip you are using is for 42lb injectors?

 

[1badTTA]

Originally posted by denn454
first off why do you disconnect the vaccume line when setting the fuel pressure? i always leave mine connected.
next thing is i was getting some knock before with the car running really rich, now that i have leaned it down it not only runs a lot better, but i get little if any knock. isn't that backwards?

You disconnect the vacuum line so you can get an accurate reading of pressure differential between fuel pressure and manifold pressure/vacuum.

Nearly all injectors are designed to be ran at around 3bar's, which is about 44psi. The chip is what ultimately controls what the pressure needs to be set to and most chip burners plan on about 42-43psi. If you have to deviate more than 1-2psi from that, then you have another problem.

Someone will know for sure, but didn't "009's" come in 2 different sizes? If so then you may have the 42.5lb/hr injectors and a chip for 36lb/hr injectors. That would be enough og a difference to cause you to need to turn down the FP well below normal levels.

Also, what are the BLM's looking like?

 

[redhotrod]

Just curious where you came up with 42 lbs.? He should set it wherever it works for him. Everyones car is different.

That is a good starting point if you have a new chip. When you came into the world of turbo buicks, where did you set yours? (~=around) 42lbs? 37 just sounds low.
If you try to adjust it with the vacuum on, the vacuum will pull the pressure even lower. The fuel pressure regulator is just that, a regulator, it determines how much fuel the motor should need according to vacuum/boost, boost fuel pressure should rise 1lb for 1 lb boost, and drop pressure at sitting at idle at vacuum.
Getting knock with too much fp can happen, i believe it is because there is so much fuel, some might be getting ignited in the exhaust pipe, which I'm sure could set off the knock sensor. Thats just my theory.