KOKISF

I just got lost here! The mechanics told you " leak down was good , but it looks you have a valve train related problem"??? One thing cancel the other !!! If the leak down is good , it is impossible you now have a valvetrain related problem or even a broken sleeve!!! Thats crazy.

nOS backfire ussually happends when spraying to early, some claim 3000 rpm wot is the lowest you can go others 2500 rpm wot with a ramping effect on the NOS set up. At what rpm you hit the F with Nos , what plugs you use, how big of a shot ?

abohler

The original leak down was wrong. I saw the motor pulled apart, destroyed a piston, and scored a sleeve. I wasn't spraying until near 4k rpm and off at 6800 with a wot and window switch. Running a degree colder plugs, 150 shot with a c16 stand alone fuel cell, I am thinking too much fuel got pushed into the manifold a couple times and the motor just couldn't take it any more.

idoke1

iTrader: (5)

I was actually considering nitrous as my next mod but hearing all this makes me very nervous. Notherwise to hijack your thead but how much did you guys spend on nitrous and installation?

Bakewalk

This is 1 person and 1 issue. There are many of us that have been running nitrous for a few years with no problems at all. Ask around before you are scared off...

idoke1

iTrader: (5)

^^True but I'm not scared. I'm nervous because I daily my F and it would suck if worst comes to worst. How much did everything cost you guys for nitrous set up and labor?

Bakewalk

My advice would be, don't go cheap. If it cost you more so its done right, this is the only way to go. I paid over $3500 for my setup, worth every penny and wouldn't of paid any less! Wet system with 2x 10lb bottles, progressive controller so I can run it right from WOT. I run it from idle at the light to the end of the track.

idoke1

iTrader: (5)

^^Thanks bakewalk! I am relatively new to nitrous but i do understand how it works. I needed a heads up on price plus labor so I know where to begin. Did you change the spark plugs? If you did, which plugs did you get? Also, 91 octane gas is the highest in CA besides race gas that will probably never put in. What size jet would you recommend for 91 octane gas along with replacement sparkplugs (if applicable)?

Bakewalk

I'm still running my stock plugs. I'm usually running 91 octane only when racing as well. I tried 105 octane last time and didn't gain any time on my pass.

I sent you a pm with a whole bunch more info...

93MSB

iTrader: (8)

Nitrous outlet kit?

ihiryu

iTrader: (7)

Hmm, most nitrous backfires involve blowing up the intake manifold. Like seriously. I find it hard to believe that you blew a piston after a nitrous backfire.

Maybe it was running lean? I've only had one nitrous backfire on my Infiniti, and it blew the intake off the throttle body. I was also running a small shot (75)

ihiryu

iTrader: (7)

Also let me school some guys on how a nitrous backfire happens. It's not from fuel puddling up, well it can be. If you're running too big of a fuel jet, on a SINGLE jet, then yes, fuel can puddle up, but that normally doesn't happen.

1) Ignition timing TOO retarded (we don't have timing control, so I'll skip this, unless someone just wants to know)
2) Lugging the engine.

So if you lug the engine, the engine is spinning slower than the wheels (1:1 ratio, which I believe is our sixth gear?)

So fuel, nitrous, and air are all in the intake manifold, and since the motor is spinning slow, it eventually fills up the intake and has no where to go, so the explosion happens in the intake manifold. Remember what nitrous actually does, it chemically cools down the intake charge, and when it ignites, it becomes a bigger explosion. Which is why nitrous, happens instantaneously. When you look at a dyno chart, the MOMENT some starts spraying, you see a big jump in TQ.

Which is why they tell you not to spray at such a low RPM, because the instant torque can break/bend rods!

So for instance, if you were spraying at a high gear/low RPM, you'll have what's called "reversion" in the intake manifold, and POP! Something's gotta give.

Sylvan

iTrader: (6)

were you running an AFR gauge? I wonder if it went lean? Was the piston destroyed as in broken ring lands or a hole in the piston?

lobuxracer

iTrader: (2)

Doesn't sound like there was time to actually hole a piston. More like shattered ring lands and bent rods. I've got a few of those laying around too.