I did a fuel pressure test today and got the following results-

40 psi with just ignition on
49 psi with vaccum line disconnected and engine running at idle
43 psi with vaccum line connected and at idle

Do those readings say I need an adjustable FLP, or my stock one is still fine. What's the optimal fuel pressure, and what's the way to set it with an adjustable fuel pressure regulator.

Also when I turn my steering wheel all the way, my rpm's drop a bit. Is this fuel related? I have a 255 lb/hour fuel pump

 

depending on what you have done to the car so far i would say 43 is good if you havnt done anything, but if you have like a cam and heads then you should have at least 48psi, even stock it is good to get a adj. fuel pressure regulator.

 

Lot of different opinions on this subject. When I did my aeromotive adjustable fuel pressure regulator, I set my pressure to 48 PSI at idle with the vacuum line disconnected. With the line connected, I was reading 39-40 PSI.

As far as turning the wheel at idle, the reason your idle speed drops is because you're putting load on the powersteering pump.

 

Your fuel pressure sounds fine to me.

 

thanks guys for helping.

I was wondering if I should check my fuel pressure at WOT too? I am installing N20 wet kit over the winter break. Wouldn't it be safer to have adjustable FPR with 150 shot?

 

When you pull the vacuum line off, that simulates WOT to the regulator. No need to go to "real" WOT.

 

yes you should by the FPR when you pu tthe N2O kit on it will save you from blowin your motor because you dont have enough fuel.

 

I somewhat disagree with that.

Particularly on a modded engine, it is a good idea to check the WOT fuel pressure by actually going to WOT. Reason is, although at idle with the vac line off you will get the same pressure at the regulator as at real WOT, fuel consumption rates differ massively between idle and WOT and if the pump is not supplying enough volume to keep the rails full, pressure at WOT might drop. You'd never know that by simply checking pressure at idle with the vac line disconnected.

 

I wish I could check fuel pressure at WOT too, just to be sure, but I only have a mechanical gage with a short fuel line, not enough line length to tape the gage on the windshield

 

Technically you are right in any other situation. But he has stated above that he has a perfectly adequate fuel pump and that he is trying to determine weither his FPR is functioning correctly which can be done very easily with the above recommendation by Rob. It is, however, (if you can) a good idea to check the pressure at "real" WOT throttle. Your readings look good. But if you are planning on using NOS you should invest in one. Nothing like running a cylinder lean with NOS.

One more thing to add. An adjustable FPR is only a temporary fix. Long term fuel tables will be readjusted by the PCM after a matter of time no matter what you set you FPR at it will compensate to bring it back into factory specs. But it helps with short term such as a 1/4 mile....

 

I pretty much agree with that.

In his situation with "normal" pressure on the higher side of the scale, I doubt that his stock injectors can flow enough to seriously reduce the fuel pressure.

 

Oh I agree with you there, in this specific case its probably not necessary. But in general it is a good idea to verify the true WOT fuel pressure to rule out a weak pump if its not already confirmed good.