NOS gremlins

skinz L98 · 05-14-2004, 04:47 AM

I have a 86 that I'm having problems with. What should the fuel pressure be at the fuel sileniod? It goes dead rich when I try to use the nos, to the point of stalling the motor. I took the sileniod from the schrader valve and put it in line because the fuel pressure would drop to 18 psi. when ingaged. I put to 12-903 holley pump in thats good for 800 hp. But now I think it's too much fuel pressure. the "kids" at nos said the pressure does'nt matter. I disagree. Should it be the same as a Carb. set up? (it's a 150 hp set-up). I went threw the whole nos side as well. New sileniods,filters, screens, bottles, etc, etc. Please help. Oh by the way it's a duel fogger system and the bottle is alway's at least 950 psi :mad

[Modified by skinz L98, 9:11 AM 5/14/2004]

jburnett · 05-14-2004, 03:07 PM

NO... EFI systems use different jets than carbed systems. I suspect you have way too much jet in it if you're thinking it runs the same pressure as a carbed system. You'll see 45 psi or so at the solenoid (depending on what your FPR on the rail is set to). You need smaller fuel jets for the higher pressure.

I run a separate fuel system for my N2O that uses its own fuel cell and it IS a low pressure system (like a carb) and it makes it easier to tune.

I don't have a Holley p/n list in front of me so I'm not sure what that pump is but if you replaced your stock EFI pump with it and it's NOT an EFI pump you ain't going fat, you're going hella-lean... 18 psi is WAAAY too low for EFI...
-Jeb

69 N.O.X. RATT · 05-14-2004, 03:17 PM

I can't believe NOS tech would tell you something like that, either you misunderstood or they are truley idiots. Nothing in a NOS system means more than fuel pressure, timing is a distant second.

skinz L98 · 05-14-2004, 08:35 PM

The 18 psi was when it was plumbed into the fuel rail with the OE pump. The pump I have now is 70 psi holley. I t'ed into the main line. I did'nt like it going to the schrader valve. I know it's fat. NOS said "you can have 100 psi, it does'nt matter because the jet's do the regulating".I said good bye because we all know better then that. Now I need your help. I put a gauge after the fuel silenoid and it has 45 psi. right before it chokes out the motor. must be the jeting then? anyone know what sizes for 150 hp.?

[Modified by skinz L98, 12:39 AM 5/15/2004]

[Modified by skinz L98, 12:41 AM 5/15/2004]

skinz L98 · 05-15-2004, 11:42 PM

Figured it out. Wow, thanks for the info

korvette4u · 05-18-2004, 10:41 AM

What should the fuel pressure be at the fuel sileniod? It goes dead rich when I try to use the nos, to the point of stalling the motor.

pressure at the fuel rail should be 40-45psi. as for the rich effect....it will at idle.. becuz of the extrta fuel...assumming your testing the fuel delivery and the operation of the sloenoid

now the nos is to be injected @ 3000 rpm or better... when mine hits there without nos it stumbles as well.. (while testing fuel delivery), but when nos is on .. whoa ..