Fuel pressure question

[mike93lx]

So my car is running pretty rich, and I think my injectors are too big, but i need to get a temp fix for right now. I am estimating my combo at around 400 flywheel horsepower, maybe a bit more/less. can someone recommend a fuel pressure I should start at to help tune it and how will i know i am about right? i know i can read plugs, but is there an easier way?
Thanks

-Mike

 

[Rock777]

I would like to know the easiest way to tell what fuel pressure is optimal as well, without having a dyno done obviously. I have it set at 39 right now with my new setup, but just want to make sure it is pretty close.

 

[HISSIN50]

the puter will trim the pulsewidth if you are close. IIRC, Jrichker has posted a link which shows what pressure one might want to run (with regard to duty cycles, etc).
good luck.

 

[5spd GT]

So my car is running pretty rich, and I think my injectors are too big, but i need to get a temp fix for right now. I am estimating my combo at around 400 flywheel horsepower, maybe a bit more/less. can someone recommend a fuel pressure I should start at to help tune it and how will i know i am about right? i know i can read plugs, but is there an easier way?
Thanks

-Mike

Set your FP at 39psi with the vaccum off the AFPR and a finger or something to "block" the vaccum line while it is disconnected...clockwise make the FP go up and counterclockwise makes it go down...

That is the setting I have on my car and I have an FTI combo with the same 30lb injectors you have and the car runs good

You have closer to 340 flywheel horsepower...at your current N/A setup...

The car will smell rich at idle but it is fine I promise...and my plugs look good

 

[jrichker]

Use the SOP meter...

Get one of your buddies to ride along with you. Find a level stretch of road where you can do some testing. Don't choose a speed range that will make you shift gears, the shift quality & speed will affect your results. Use 2nd or 3rd gear and do a run from 2000 RPM to 5800 RPM. Call out the RPM as it increases and have you buddy record it and the elapsed time. If you have one of those cheap digital watches like I do, a stop watch is built in. Start the fuel pressure at 36 PSI, vacuum off and make a run. Turn it up to 37 and make another. Be sure to reconnect the vacuum every time you set the pressure. Keep turning up the pressure and making runs until you notice a drop off in time. If your bud was careful to record the results, you'll have a nice chart to use to find the optimum pressure.

 

[Michael Yount]

The ecu will control mixture within it's abilities to do so by altering pulse width - how long the injector is held open. It's gonna use the O2 signals to set mixture according to it's parameters. If your car is really running rich, because the injectors are too big, the computer should signal that something's wrong with error codes and a check engine light. If that's not happening, it's because the ecu is using it's adaptive strategies to lean out the mixture by shortening pulse width.

You should set the fuel pressure at the stock level 38-40 and leave it alone. If you have injectors that are too big (not sure what that means) the proper fix is to recalibrate the maf or use a chip to solve the problem. Messing with fuel pressure is simply not a viable long term solution to a mixture issue.

What makes you think you're running rich? Although you probably could use 24's just as well, a properly calibrated ProM with the 30's should be able to work with your combo just fine. Despite your desire not to do it, a wide band is the only way to really understand what your mixture is doing. Absent that data, you're pretty much guessing at things. And based on the time/speed/mods in your sig, I don't think you're making as much HP as you think you're making.