Ok.. i have a fuel pressure regulator on my dohc ZC and i have it set at about 50 psi( when i take out the vacuum hose off the manifold) then at about 41-42 at regular idle.... well.. i was checking the pressure when i gave it some gas and it seems that when i step in the gas the pressure rises about 5 psi for about a second and then it drops back to 41psi even if i keep the engine to about 4-5k rpm... shouldnt the pressure stay constant or at least rise to 50 psi when at WOT?? is it normal?? any help will be appreciated...
thanks in advance

 

the pressure changes along with manifold vaccum or pressure. when you open the throttle the vaccum goes to 0 but unless you hold the throttle wide open and have a load on the motor to keep it from over revving the manifold will very quickly return to a state of vaccum and the fuel pressure will drop again.

Think about it like this. The vaccum hose that is connected to the manifold is pulling vaccum on the top of the diapragm in the fpr. This is lessening the pressure that the spring inside the fpr is pushing with and lowering fuel pressure. When you reduce vaccum by opening the throttle the spring has and easier time pushind down and restricting fuel flow back to the tank and the fuel pressure goes up. Get it?

 

41psi is a lot for a zc with the hose on

I never turned mine up past 32,33 past that and I lost hp
stock is 29-30ish

here is my dohc zc dyno with a header and exhaust and a stock pm6


Thats not the best dyno but I have other ones and my car always liked 32(with the hose on)

 

racerxadam- thanks for the explanation, i understand better now....

89civicdx - thanks for the info on your ZC, the reason why i thought i would need more fuel is because of the mods i have... i have a ported and polished head, 5 angle valve job, intake, headers, exhaust, and a 60 shot nitrous, and other minor things.... however, i did notice that the car ran a little better when i have the pressure down... i think i might lower it a few psi's... any recommendations???
thanks

 

any suggestions on how many psi????anyone??

 

according to his Dyno chart...i would say 38

 

I run 42 on a Z6, and that I think is still a tad too high. I would suggest 36-40. IMO

 

I think ill try around 40psi..
thanks for the help....