Nitrous experts, I have questions/need help.

Fett

New Member
Nov 2, 2004
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Ok, I might or might not be having a problem...

I hooked up a 75 dry shot before my last track visit, got some runs in with the bottle off, then turned it on and didn't feel anything different. I wasn't expecting to feel like an 11 second car, but I figured it would pull slightly harder. Everything seemed to happen faster in my head, but the times do not reflect that. My times were actually a tad slower, but I think that was due to my mind and body not being in sync....because I was not sure what to expect. Plus I used my tweecer to put my timing back down to 10*, where as my earlier runs I was running 17*. I was running 26" slicks and was NOT spinning.

Well today I started playing with it to see what was happening. I unhooked the line going to my intake and with KOEO I held down the gas to trigger the nitrous solenoid (throttle body switch at WOT). The entire time I had the pedal down, it sprayed. So I purged the line and took it out to our test road, with my Nitto drag radials.

I shifted into 2nd, and held 3/4 throttle until 2500rpms, then stomped on it. I could hear the solenoid kick on and the car took off like a bat out of hell....until about 3200rpms, then it kept accelerating normal. It might have been slightly harder than normal....but it wasn't pulling the same from 3200-5500 as it did from 2500-3200. I did this same test in third with the same result. Then I decided to feather the throttle, hammer the gas and as soon as that initial kick was over, I let off and quickly hammered it again. It seemed to pull hard for a few RPMs on each initial WOT, but then it would quickly die off again.

It almost seems like it only sprays for that first few milliseconds then cuts off, so each time I nail it WOT it would spray, then it would stop. But like I said, I tested it with the car off and the line disconnected from the intake just to see if it continuously sprayed with the pedal down, and it did.

My setup is in my sig, the only thing missing is my tweecer and the nitrous.

I have the same basic tune in all 4 settings for the tweecer, the only difference is I have a different WOT timing advance in each one.
#1 is an extra 5* for a total of 15* total advance at WOT.
#2 is an extra 3* for a total of 13*....
#3 is 0* for a total of 10* stock....which I used for the nitrous.
#4 is an extra 7* for a total of 17*, which I used for my 13.1 run.

The nitrous setup is a dry setup with a throttle body miniswitch for WOT, with the nozzle in the intake tube right before the throttle body. I didn't hook it up, so I can't be sure if it isn't a vac issue or anything while the motor is running. When I tested the line, I did so with the engine not running and the line disconnected from the intake....just like a purge, just to see if it was spraying continuouslyh with the gas pedal at WOT.
 
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do you have a window switch or anything like that that could be cutting out the nitrous because it is set at a low rpm?

Not from what I can see, the solenoids are hooked up to the fuel regulator vac line. The relays that power the solenoids are run through an in-cab switch to turn it on, and a throttle body mounted miniswitch to activate them. Let me go get some pictures....hopefully that will shed some light on it.
 
Not from what I can see, the solenoids are hooked up to the fuel regulator vac line. The relays that power the solenoids are run through an in-cab switch to turn it on, and a throttle body mounted miniswitch to activate them. Let me go get some pictures....hopefully that will shed some light on it.

Now this is interesting. If they are mounted up to the fuel pressure gauge is there a safety to kit it off if there isn't enough fuel pressure?
 
I would go over the install instructions again step by step and make sure everything is installed properly on your system. Forsure what is happening is the fuel psi sensor is shutting your nitrous off on you. So it is saving your engine from a lean situation. Check everything again and perhaps you need the fuel psi booster.
 
Ok, I examined my setup and it is exactly how it looks in the picture on page 9. So you are saying that I might not have enough pressure and it is cutting off the nitrous?

Is there a way to "test" that without getting the kit in chapter 3? In other words, at this point it is a theory that the pressure is the problem, can we test that theory easily?

Exactly how does that cutoff switch work anyway? Does it detect low pressure? Is that what could be happening, it sprays but when the nitrous starts spraying it doesn't feel the extra fuel pressure and then cuts off the nitrous?
 
I will go back over my install again, and double check everything. I am really hoping that I don't need the PSI booster, because I was trying to get back out to the track on Friday night....for one of the last chances before they shut it down for the summer. I don't know if I will have time.

BUT, I am not going to risk ruining my engine....so I will do what needs to be done and not "cheat" it.
 
Also....and this is a really stupid question....

Is that kit considered a "wet kit"....so I would possibly be able to go with a larger nitrous nozzle in the future? Just curious. :)

I wonder if I have my regulator set too low? I should check the pressure in the fuel rail now just to make sure. Could bumping the pressure help at all....or would that just be wasting my time?
 
I just gave everything a quick once-over, just to see if anything obvious sticks out.

The setup is exactly how it is pictured, but I don't see an electrical switch anywhere. There is nothing hooked up to my fuel rail anywhere, except the vac lines going to the solenoids that are teed into the vac line to my adjustable pressure regulator. My test port on the supply line still has the cap on it with no electrical switch that I can see.

I also noticed that the vac line going from my vac tree to the cannister in the passengers fender is cut. I don't know if that would effect anything, but I know it is something I need to fix tomorrow.