cavellm

What should the fuel pressure sit at? I've got a guage hooked up between my regulator and the fuel rail. With the vacuum line attached, it's at about 33-34 psi. When the vacuum line is removed, it goes up to about 41-42 psi.

I just got a few extra feet of fuel line, so I'll be able to figure out if it stays constant or drops while at boost and/or higher rpms.

I've got 550/1600 injectors, Keith's secondary rail, sx regulator, and a Supra TT pump.

Scrapiron7

I see about 2.5 bar on my FP Gauge under idle, and up to 4 bar under boost. But that's on stock injectors.

broken93

That sounds correct. IIRC, the pressure at the rail should be 41 psi differential at atmosphere+. So it sounds like your FPR is working just fine

cavellm

Cool. So I know I've got good pressure at idle, now to test under boost. Also hoping that a worn out o-ring in the y pipe might be causing my lean at higher rpms problem I've had for a while. If it's leaking enough air to have my a/f read lean past 6k rpms and under boost.

Hopefully I'll have it ready for a weekend dyno test..

Thanks for the input guys!


Cavell

Kevin T. Wyum

Wouldn't have any effect, fuel is based on the pressure at the manifold, air temp and RPM, any leaks prior to that won't have an effect. If you're leaning out up top your map is wrong or you're running out of pump at higher RPM's.

cavellm

So if pressure drops then I should replace the pump. And if pressure stays constant, I need to re-tune the car.. Seems simple enough! Thanks Kevin!

I'm gonna be mad if its the pump though, since it has less than 3k miles on it.

But the weird thing if it is the map, is everything below 6k rpms is extremely rich. Weird that something would make it lean out very noticably above a certain rpm. And the same a/f curve at 12 psi and 17psi. I'll check it out tonight.

Kevin T. Wyum

Almost got it, the fuel pressure should go up 1 psi for each psi of boost. In your case at 17psi you should see your base pressure of 40ish psi plus the 17 psi throughout the RPM range while that boost is maintained.

Kevin T. Wyum

cavellm

Looks like I'll need to throw it on a dyno to richen it up a bit. Made a couple runs on the street and watched the gauge hold steady at 56 psi while I was running 12psi of boost. I didn't want to take it too far up in the RPMs since it was running lean, but didn't drop at all by the time I let off the gas at 7k RPMs