Decided to hit the nitrous button in second gear just to see if things were working ok. Hit the button, nose of the car lifted, shifted to 3rd and not soon after it popped through the exhaust once. I let off the button and just ran out the rest of the way on the motor. I'm curious what causes that flame out the exhaust? Is it a lean, rich, timing or some other condition? Fuel pressure is set at 5 1/2 and bottle pressure was at 1000 if I remember right, jetted for a 210 shot.

 

I guess no one knows?

 

backfire out the exhaust means rich.. or the timing could be off

 

Timing is set at 36, normaly 40. I'll try backing down to 5 psi instead of 5.5.

 

Stick or auto?

Like he said, backfire out the exhaust is usually either rich or ignition related. N2O creates a much more oxygen rich environment in the chamber and is more tolerant of excess gas (I’ve said it before, most N2O kits jet for about a 6:1 a/f ratio, way rich for best power but safe and they usually don’t have any problems), and one thing for sure you don’t ever want to run lean when spraying.

I’d put money down on the ignition anyway. Timing is either retarded or more likely the change in load after the shift is causing a misfire. Assuming you’re running an appropriate ignition I’d try closing your plug gaps a few thousandths, maybe like .005” and see if it changes.

 

Didn't see your post till now... Auto trans, the single pop came about 3-4 seconds after hitting 3rd. Plugs are gapped at 35 and I run an MSD ignition. I'm just going to back down the fuel pressure and try it out again later this month. Friend's car had the distributor rotor eat itself up on a nitrous pass, looked like he had afterburners under his car

 

might want to gap the plugs down to .030.

 

well, that's a perfect example... ignition problems, probably causing misfires resulting in afterburners.

I'm not sure why everyone insists on running big gaps with power adders. I’ve never seen the kinds of gains (well any at all for that matter) that you do with doing it NA, and things are so much easier when you run a tight gap… it fires consistently, parts don’t burn up…

Usually when someone is having trouble I recommend knocking them down to around .020” and go up from there. Without an ignition box a gap that small will cause a rough idle with a lot of stock ignitions, but work fine under load or with an ignition box, and should eliminate any ignition related issues. Most of the fast/reliable power adder cars that I know of are running gaps in the .024” range.

I’m still pretty much in shock that when I talked to the engineer that designed a few of these boxes about my current crane hi-6+lx92 setup, at first he insisted that I’ll want to run something more then .045” with boost and “even a little spray on top of that,” which is totally counter what I’ve seen work with any other ignition system so far. After talking to him for a while he finally said “well, you’ll probably want to try a little less,” but still was suggesting gaps way out of the range of what is considered normal for that kind of application.

I’m not sure if I’m going to go with his recommendations or at least start with what I know will work and work my way up when I have time to experiment.

 

Well just to update, that half a pound of fuel pressure I took out made things great again it seems. Nice crisp response and good power till I ran out of bottle hehe oops. Here's a video of the run. I'll try the smaller gap on the next set of plugs since the 250 jets are going in for next weekend.