Well, I just got my kit installed and was using it for the second time when I had a horrible nitrous backfire, it blew my lid off and broke the clamps, and blew a hole in the back of my intake. It was the weirdest thing, seconds before the backfire happened it sounded like my car was hitting the rev limiter (but it wasnt, it was at about 6000 RPM and my limiter is set at 6600) and then BOOM! I have a heads/cam car and was using a TNT 100 shot with a window switch. I dont know why the hell this backfire happened.

I have a few guesses why it happened can anyone confirm these suspicions:

1. I didnt pull any timing while using the 100 shot, I was under the impression I would be ok with that size of a shot.

2. I am still using a stock fuel pump with a wet kit and a heads/cam car. I dont see why a lean condition would cause a backfire, but does this possible have anything to do with it?

3. I was only using premium octane, and my compression ratio is 11.1:1, should I have been using race gas?

 

Hmm Im interested also.


Did you spray at a higher psi? like 1100+?

How muching higher than stock timing are you running with the heads and cam setup? I know stock timing works with a 100 shot. 150, 2 less.

I dont think fuel pump has anything to do with it.


I think its because of compression and too much timing....

Let see what others say as this is just my guess.

 

Mabey you werent at high enough psi on the nitrous side....

 

I live in salt lake city with an alitude of 4400 feet, so i was spraying with a bottle pressure of about 1250 psi, but that should be fine in utah because of the altitude. also, the only timing change i have done is from 800-1200 RPM because of bucking issues. I advanced it about 2 degrees in this range, I did not change any timing anywhere else.

 

The last post was actually my post. I wasl ogged in under my friends name.

 

did your shift light go off what are you shifting at?

 

I dont have a shift light, but I was definetly shifting at about 6000. I dont know what the hell the problem was. It seems everyone I know who has an ls1 and has used nitrous has had backfiring issues and I dont even want to deal with it again, it's ridiculous. I'm going to sell my nitrous kit, forge my motor, lower my compression, get new heads and turbocharge my motor. I thought I could use nitrous as an inexpensive means to powerful runs, but have learned that it is much to finnicky. I guess it's true that nothing good comes cheap.

 

There's something else that is wrong, I know TONS of people runnign alot more then 100 shots and having no problems. Do you have a window switch, fuel pressure safety switch? I'd guess that at higher RPM your fuel pump couldn't keep up and it went way lean.

 

Yep you likely went lean....Thats why I preach wideband....Could have either been because the fuel pump couldnt keep up or a common fuel noid failure. Id bet the "rev limiter" you describe was heavy detonation...

 

its not the fault of the LS1 or the nitorus... **** with everyone around here you would figure it came stock on LS1's.. no what gear were you in.. 1st and 2nd motor revs so quickly the stock tach can't keep up.. hell i blew the tires off once and hit the limiter.. the tach was still at 5700.. and my limiter is over 7k..

 

ya i have had this happen myself..that is why i bought a shift light..could have possibly contributed, and you might have actually been hitting the limiter, just didnt think so b/c the tack was behind..

what RPM does your window switch deactivate the nitrous?

Jon

 

Why would a lean condition cause a manifold explosion? (just wondering for my own knowlege)

 

I would assume this would happen due to the fact you're pushing more n2o than fuel into the manifold . If you start leaning out you start running a higher chance of detonation. Not 100% on this, but maybe an expert can chime in?

 

stock timing and a 100 shot is fine, as is stock timing for a 150 tnt shot (i get ZERO KNOCK during my runs- the only knock i may get is one "ping" or spike when the nitrous activates- which im going to tune out).

im running a racetronix fuel pump also though. i'd be willing to bet the stock fuel pump is the issue. a friend of mine is running a zex 125 shot on a si ls1 (zex `125 shot= about the same as tnt 100 shot) and he was dropping fuel pressure as the rpms got higher during a nitrous pass on his stock fuel pump. he had the same cutting out issue like you described but i guess didn't stay into it enough to get a backfire.

don't sell the kit- buy a fuel pump and get some sort of tuning equipment (i reccomend hptuners) so you can log and see what is going on, then make changes accordingly. you can't expect to just slap the kit onto a h/c high compression motor on the stock fuel system and expect everything to work out perfectly.

edit- i just saw that you have hptuners. how did the log of the run look? WHAT was going on with the car will tell the story.

 

Yeah i think you need a fuel pump.

 

I believe you hit the rev limiter before the factory tach could read it and then went lean which will cause this problem. I had a similar situation and it took out the back of the intake, maf, lid, 4 valves and punched a whole in heater core housing. I set my window switch 2 to 4 thousand rpm's below the rev limiter just to be safe. Also like other people said, get a fuel pump as the stock is not designed for spikes in hp levels. Good luck

 

Nitrous backfire?? IOh... I know all about that! Luckily I didn't have my new hood on at the time... Beleive it or not, there was no motor damage, the lid didn't even break!!!

 

Your big mistake here is the higher compression engine + 93 Octane + nitrous with no fuel pump. Also what spark plugs were you running? Dont blame it on nitrous and go and get a blower cause you know if you neglect the safety stuff like tuning and fueling with forced induction you will still have issues with **** breaking, its all part of the owner/driver mod. Do it right and it will run fine. There tons of us running 150++ shots on stock blocks.

I really want to know the plugs you were running.

 

big mike- where the *** is the hood!?