Adjustable Fuel Pressure Regulator

General engine questions/issues that aren't specific to the other categories
 Reply
User avatar

Adjustable Fuel Pressure Regulator

By BLaCkSiLo
- Thu Apr 02, 2009 6:55 am #107647 Hey Guys,

alright, so here is the thing, i'm installing a free B&M fuel pressure gauge and a B&M CommandFlo adjustable fuel pressure regulator on the fuel rail.

so all is dandy, i install it correctly, look for leaks while primed/priming, all looks good to go and i set it at the pressure i read on the gauge before i took the old one off set ~40psi when primed and ~37psi while running.

i start the car and it runs like hell, runs really chopping, popping in the exhaust and if you floor the throttle, it would just bog and then eventually go after about 3000rpm. also, i managed to drive it home and if you put any sort of load on it, it just bogs, jerks and stumbles like it's not getting enough fuel.

so i kept adjusting the pressure up and up to eventually a point where it would idle but still bog, i'm at about ~45psi running pressure. is there a limit that you can go to high? and why if i kept the stock fuel setting would it make my car run like piss? it's a d16z6 in a 94 ex if it helps...

hopefully someone can clue me in here, everytime i incrementally turn up the pressure it seems to get better but i don't want to go to high, i do have a header/exhaust and intake.

thanks a bunch,
James :thumbdown:
User avatar

By GSRSI
- Thu Apr 02, 2009 7:47 am #107652 i hope some one can help you ive never really messed with adjustible fpr's
User avatar

By suspendedHatch
- Thu Apr 02, 2009 5:11 pm #107738 Adjustable fuel pressure regulators are a complete waste of money. Is your setup over 80% duty cycle? Why not get bigger injectors? You know the factory injectors are good to about 160 wheel hp. How much are you making?

The ECU measures the O2 content of the burned fuel mixture and adjusts the amount of time the injectors stay open. So if you increase the fuel pressure, the ECU will open the injectors less. What have you accomplished? Well for one thing, if the injector time at idle is less than 1 ms, they wont function properly.

The symptoms you describe could easily be caused by TOO MUCH fuel.
User avatar

By BLaCkSiLo
- Thu Apr 02, 2009 10:15 pm #107854
suspendedHatch wrote:Adjustable fuel pressure regulators are a complete waste of money. Is your setup over 80% duty cycle? Why not get bigger injectors? You know the factory injectors are good to about 160 wheel hp. How much are you making?

The ECU measures the O2 content of the burned fuel mixture and adjusts the amount of time the injectors stay open. So if you increase the fuel pressure, the ECU will open the injectors less. What have you accomplished? Well for one thing, if the injector time at idle is less than 1 ms, they wont function properly.

The symptoms you describe could easily be caused by TOO MUCH fuel.


the ONLY reason i put the AFPR on there is because it was free, i figured if i set it to the stock setting that i read on the gauge beforehand, there would not be issues but No Dice. i'm installing a VEX nos kit along with this FPR so i wanted to have some adjustability. but currently i am not making anywhere near 160whp, but during the nos shot i will be. (that gets into a whole nother chapter....) currently i have not even filled the NOS bottle so that's not my problem yet.

i'm going to try and track down a stock regulator and put that on there, i have read that the B&M ones suck something fierce, what happens if you have too low of fuel pressure?
User avatar

By BLaCkSiLo
- Fri Apr 03, 2009 1:32 am #107936 so i reverted back to the way it was (took off the gague, replaced banjo bolt, went to the junkyard, got a stock FPR) and now it's still doing the same thing... i'm completely at a loss now, could the filter get clogged?

it also has a hard chatter now when you engage the clutch to try and take off, it rattles and josles everything in the car, i might drive the thing off a cliff

any advice would be good..what about the ECU, can you fry that somehow?

also, the timing can't be changed all of a sudden right?
User avatar

By BLaCkSiLo
- Fri Apr 03, 2009 3:50 am #107962
teal_dx wrote:do you have a check engine light? did you touch anything else on the car/engine?


no, i did not touch anything else, and im kind of losing my mind over it.
The engine is running like crap, like 3 cylinders, but no change in the timing, No CEL, unplugged the ECU while did the comp test (1:189 2:190 3:192 4:190) and spark plugs look great, brown with a hint of white, not wet or burnt or fouled...

anytime the engine is presented with a load, it just falls on its face, then kinda picks up and goes, stumbles and runs fine above 3k rpm's which thinks timing? i dont have a wideband O2 sensor to monitor the A/F.

thanks
User avatar

By teal_dx
- Fri Apr 03, 2009 3:58 am #107967 if the timing belt is not tensioned properly, it is possible for it to skip a tooth.

You try resetting the ecu? (disconnect battery for ~20 mins)

if it was timing, I think it would run crappy at all rpm, not just under 3000.

You did not unplug any sensors when installing the FPR right?

I'll keep thinking...
User avatar

By BLaCkSiLo
- Fri Apr 03, 2009 4:35 am #107979
teal_dx wrote:if the timing belt is not tensioned properly, it is possible for it to skip a tooth.

You try resetting the ecu? (disconnect battery for ~20 mins)

if it was timing, I think it would run crappy at all rpm, not just under 3000.

You did not unplug any sensors when installing the FPR right?

I'll keep thinking...


i did the timing belt about 6 months ago with a new pump/tensioner/belt, was running just great until this little mishap here

i did reset the ECU, several times actually, and it's still not throwing a CEL, even when you put it under a heavy load and it stumbles hard.

the only reason i keep thinking timing is because of the poor running conditions. but i was talking to a few people and what if somehow with some extra pressure (like the regulator is junk and stuck open) could i have knocked something loose such as particles go... i'm going to replace the fuel filter and maybe check out the rail and individual injectors for pluggage?

i don't think i unplugged anything, i will go double check though, a buddy said the MAP sensor if it gets unplugged will go haywire, what about the TPS?

thanks for your help, this one has stumped me and like 4 others...
User avatar

By BLaCkSiLo
- Fri Apr 03, 2009 8:06 pm #108141 at this time i was running my nitrous lines, and mounted the zex box on the inner frame rail on the passenger side. i have no idea how this could cause any problem, i didnt fill the nitrous or even turn on the box yet because this crap happened.

today i took the bottle and clamps out because i mounted the bottle in the trunk, and thought i might have drilled into the fuel tank but how could that cause a problem? the fuel pump does not pressurize the tank correct?

here is my gauge and it is rock solid, set at ~37psi (which is stock) and when you give it throttle at idle, it goes up to around ~42 then back down.
also, when you detach the vacuum hose, it rises to ~47psi (which i thought was in spec)
*sorry for the blurry pic****
Image

By That Guy
- Tue Apr 07, 2009 7:34 am #108799 Is it possible that you gave it too much fuel and fouled up a plug? try replacing the plugs, or at the very least pull yours and see how the burn looks.
User avatar

By boosted94
- Tue Apr 07, 2009 12:33 pm #108815
BLaCkSiLo wrote:and spark plugs look great, brown with a hint of white, not wet or burnt or fouled...


thats all.
User avatar

By BLaCkSiLo
- Tue Apr 07, 2009 2:45 pm #108838 i thought i had attached the picture of my plugs...they all look the same as this,

*sorry for the blurry
Image

so everything seems to be fine, i checked the cam/crank timing yesterday, i timed it with a timing light as well, the fuel pressure is good and the sparks look good

how about sensors? could a TPS or MAP sensor cause the timing to go out the window?

it seems to do fine when it's cold, but as it warms up, i can watch the timing with the timing light get worse and worse....
 Reply
Return to Engine - General