V-10 Killer

iTrader: (22)

I'm finally ready to start dialing in my nitrous system, but noticed last time at the track that at WOT N/A, my fuel pressure would drop down to 44 psi. It was only 55 psi at idle. To me that seems unusually low for a Racetronix intank setup. I'm used to seeing 62 psi at idle. I only had ~1/4 tank of gas, but I'd have thought it would be enough.
What should I consider a minimum safe fuel pressure not to cross while spraying?

CAT3

iTrader: (9)

Jetting I believe is for 55psi, to take into account the pressure drop during a run. 44 would be too low for me to go, unless I had my WB hooked up logging to see what was the AFR NA and Juiced. Need to look at your fuel system, maybe the basket ran low and during launch you forced fuel back of the tank etc...but you need to know before spraying. Good that you caught that too. If it doesn make a come back, rejet for lower fuel pressure, there are a couple racing math website that you can enter fuel pressure etc and get jet sizes.

Matt@HSW

iTrader: (14)

That is a bit low for the Racetronix kit. Does it seem to do it all the time when you go WOT or just that time at the track? How are you monitoring FP and where from?

Matt

V-10 Killer

iTrader: (22)

I know earlier this year, it'd run 62 psi at idle. Unfortunately, I've only had the ability to log my fuel pressure for the last 2 weeks or so, so I haven't had a good indication of what pressure I was running at WOT previously. I log it by tapping my Autometer electric fuel pressure gauge to the EIO pigtail on my HP Tuners cable. I've verified that it's within 1 psi of the gauge pressure.

I have an idea I'm going to check in the morning. Three weeks ago when I unhooked the battery to drop my tranny, I accidentally broke the loop connector off the Racetronix power cable. I crimped on a replacement, but maybe it's not a great connection. I'll see if a new soldered connection improves the situation.

V-10 Killer

iTrader: (22)

Well, I think the soldering worked. Now, I can run at least 52 psi at WOT which I'll consider ok, considering I'm using 37# injectors and making ~505 at the motor.

I tried a 50 hp shot, and didn't really see anything. No fuel drop, no swing in air/fuel, nothing. I'm gonna have to check that out, because I tested the 'noids and I know they work. I tried both stages totaling a 125 shot, and it got interesting LOL. Still saw above 50 psi almost everywhere, and air/fuel never got above 12.3:1, and no knock. However, it was humid as hell today and my 90mm throttle body froze part open (~25%), twice! Yikes!! I kept a cool head though. Shut off the arming switch, gave it a second to sweep any remaining fuel/nitrous thru the intake, and then killed the motor. Boy I'd hate to have that happen at the track (or anywhere really) where every foot of stopping distance counts.
Anyway, I think I'm gonna pull the TB tonite and look for any scuff marks and try to re-work it a little. It hangs open at 2-5% fairly often when you close the throttle slowly and I don't know why. After I dyno it next saturday, I might see about throwing in a 150 shot (dual 75's), fattening it up a little more and calling it good.

V-10 Killer

iTrader: (22)

Well, I contacted Racetronix and notified them of what I was seeing. They stated that the error was likely from using an electric fuel pressure gauge. The heat buildup under the hood can affect the resistivity of the sending unit wiring. This was verified by another reputible source, so I'll buy it.
Now back to cleaning up my throttle body...