fuel pressure

[ssj4sadie]

recently I got a new 255lph fuel pump, kirban fuel reg, and fuel pressure gauge and was wondering at what psi I should set it to. at the moment i have it 48 psi we you first turn the ignition on but then it bleeds off to about 40-41 psi during actual engine operation. I don't know what mods really matter in this area so i'll list them all. Flat top pistons(11:1), twin 65mm tb , long tubes, underdrive pulleys, and in the near future a chip. Thanks for all the help kendall

 

[PowerCobra98]

with the vacuum tube OFF of the regulator adjust it to 48psi. then put the vacuum line back on and it will probably be somewhere around 39psi at idle. Idle doesn't matter much though, just set it at 48 with the vacuum line OFF and you'll be good to go.

 

[ALLNTRL]

Originally posted by PowerCobra98
with the vacuum tube OFF of the regulator adjust it to 48psi. then put the vacuum line back on and it will probably be somewhere around 39psi at idle. Idle doesn't matter much though, just set it at 48 with the vacuum line OFF and you'll be good to go.

I'm sorry but if this is for a N/A application that is WAY TOO RICH!!! My car has every bolt-on available, a PHP stage 2 intake w/ Accufab single blade T.B., Full exhaust w/ headers, etc. and my car only requires 41 psi. of fuel pressure with the Vac. tube OFF (this simulates WOT) of my Kirbin adj. regulator to maintain a perfect 12.8:1 A/F ratio thought the entire powerband. At idle the car holds around 31.5psi. of fuel pressure. These numbers are 2psi. more fuel pressure than the car had when it was completely stock, so as you can see just a couple of psi. of fuel pressure can make a BIG difference. I don't have your full mod list to see how far you have went to improve the airflow through the engine but with exhaust and 11:1 compression I am for sure that some extra fuel will be required. The best thing to do would be to get the car to a dyno with the ability to check your A/F ratio and try to get the A/F ratio to average 12.8:1 to 13.0:1 (if your still N/A) through out the entire powerband and then you'll be good to go!;-)

 

[PowerCobra98]

Originally posted by ALLNTRL
I'm sorry but if this is for a N/A application that is WAY TOO RICH!!! My car has every bolt-on available, a PHP stage 2 intake w/ Accufab single blade T.B., Full exhaust w/ headers, etc. and my car only requires 41 psi. of fuel pressure with the Vac. tube OFF (this simulates WOT) of my Kirbin adj. regulator to maintain a perfect 12.8:1 A/F ratio thought the entire powerband. At idle the car holds around 31.5psi. of fuel pressure. These numbers are 2psi. more fuel pressure than the car had when it was completely stock, so as you can see just a couple of psi. of fuel pressure can make a BIG difference. I don't have your full mod list to see how far you have went to improve the airflow through the engine but with exhaust and 11:1 compression I am for sure that some extra fuel will be required. The best thing to do would be to get the car to a dyno with the ability to check your A/F ratio and try to get the A/F ratio to average 12.8:1 to 13.0:1 (if your still N/A) through out the entire powerband and then you'll be good to go!;-)

Oops, my bad, for some reason I thought I saw that he was supercharged. My mistake.

 

[ssj4sadie]

thanks for the info, but when i'm running nitrous should i boost the fuel pressure up. Thanks kendall

 

[ALLNTRL]

Originally posted by ssj4sadie
thanks for the info, but when i'm running nitrous should i boost the fuel pressure up. Thanks kendall

YES!!!!! Nitrous is going to make the intake air very dense and cold and you are going to need extra fuel to go with it. Nitrous is a poweradder just as much as a Supercharger or turbo would be so you will have to compensate accordingly. I HIGHLY suggest hooking up with a shop that has Nitrous experience to help you get your combo setup correctly, because Nitrous + lean = BOOM!!! :nono: ;-)