Adjusting Fuel Pressure

[Paul Perreca]

What is the STOCK fuel pressure - I will be setting it initially at this - is it 39?? Thanks - the accel afpr that i got says in most aplications, the stock pressure is 43, and i thought it was 39 - need reassurance - thanks

 

[TrunkFunk]

The factory fpr is designed to provide right around 39.
They do all vary slightly though, but the standard pressure is 39 (with the vacuum line disconnected and plugged with your thumb).

Without a dyno to fine tune it you just have to play it off feel and sound, in all regards.
Seems most cars are a little different and I have seen settings from 38-43.

The nice thing about our ECU's is they will change the injector pulse length to compensate for small changes in a rich or lean mix. The idea though is to get the best 'cone spray' (atomization) you can.

 

[luckythirteen13]

when i bought my kirban afpr they said stock was 41psi. when i tested it, mine was exactly 41psi

 

[Curse]

when i bought my kirban afpr they said stock was 41psi. when i tested it, mine was exactly 41psi

I must have gotten a defective Kirban AFPR. When I put mine on, it was not set anywhere near stock.

 

[luckythirteen13]

no what i mean is that i tested the pressure of the stock reg before i put on the kirban just to make sure it was at 41psi like they said the stock one would be. when i saw that it was 41psi i put the kirban on. dont remember what the pressure was when i put it on at first but i quickly adjusted it

 

[jrichker]

Therefore you can 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. Watch for the wind speed and direction, it can have a definite impact on your test results.

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.