InsidiousGT

Let me start with a few questions before I get into my main concern..

1) I read in a thread here that the stock fuel pump on a 02 GT will only support up to ~300rwhp. Is that right?

2) Given that, do all the numerous people on this board that run nitrous also run a secondary in-line fuel pump?


I did a couple street pulls in third gear with the window switch set at 3500-5500. Heres a quick pick of RPM vs Fuel rail pressure.

http://www.mhowland.net/share/images/nos-run.jpg

Theres definitely some instrumentation problem with the RPM (see the spikes), but I'm not too worried about that. But the fuel rail pressure definitely seems to jump around way too much. I see the initial drop right at 3500 when the NOS kicks in and it compensates, but at around 4900 it starts going all over the place and I can definitely feel it in the car.

Is this fuel pump as I suspect? If I go through the gears with NOS in each gear and only hit the NOS from 3500-4500 everything feels much smoother and more powerful.

mrtstang

I'm not sure what's happening, but my stock pump is doing fine with 373 rwhp/528 rwtq. and spraying from 3-6k. Although my tuner said it was pretty maxed out.

Frostbitten

hey send me your datalog file to: jdl2z@mtsu.edu . I cant see your fuel pump duty cycle, but that fuel pressure drop and spiking is not normal. For 100 shot I would definately add a better fuel pump inside the tank. But I wouldnt be spraying it like that unless you can get a flatter fuel pressure graph.

Adam90LX

There really is not enough data collected to make a precise diagnosis. It is true that the stock fuel pump, in good working order, will provide adequate fuel for your application. That does not guarantee that your particular pump is in good working order though. That being said, I do not think the fuel pressure fluctuation seen on the graph was caused by your fuel pump. With additional data such as nitrous solenoid status, a more precise diagnosis would be possible of course. Based on past experience though, I believe the variation seen is caused by your window switch. It appears to me that the switch may be cycling a couple times as your rpm approaches the turn off set point. This phenomena is commonly referred to as bounce in the electronic world and is a very common problem I have encountered too many times with various windows switches. Just as you can clearly see a fuel pressure transient when the nitrous system is first activated, you can also expect to see a fuel pressure transient when the nitrous system is deactivated. If the window switch is the root cause of the problem as I suspect, it is quite easy to prove. Simply bypass the window switch in your electrical circuit, and try the identical test again. If you do not see the same pressure fluctuations, the root cause of your problem has been correctly identified.

nitrous_bob

how many miles on the car ?

yes stock pump is good for about 300

i'd guess yes on the pump thats failing

no i don't use a second pump... just a 190 inline