so i haven't had my nitrous hooked up in about 15k miles or so - been a few years.
however, i just discovered piston #7 burned up.
the engine shop guy said he thought this was due to running nitrous lean in that cylinder possibly due to a distribution issue or maybe a bad injector.
but i havent used nitrous in a long time. back then, before using the HSW interface, i was having issues with the MAF not picking up the full shot so i can think of a few times were it could have been too lean.

i had the injectors tested and i'm told one of them is bad (we didn't keep track of which was #7 though because we thought symptoms were that of a rod bearing).
i have a wideband hooked up to the passenger side which indicated i was never going lean at WOT.

is it possible this is old damage which just surfaced now?

 

i had the same thing happen to my car a few years ago only not that bad. I used to spray my car for a few years and probably atleast 12-15 bottles worth of 100shots. never noticed any side affects after i removed the nitrous until it started smoking on decel pretty bad. WHen i pulled it apart #7 pistons ringlands fell apart.

 

I sprayed my car multiple times back in the newb days when I knew nothing about needing a tune. Broke ringlands in 7 pistons. Drove the car like that for over 10K miles after lol. No smoke out the exhaust, just huffed like a chimney out the oil cap. All 7 pistons looked like fastassls1maro's. I bet that piston was chugging along the whole time like that being that the cracks have smoothened out and are not fresh looking.

 

Detonation.

 

Ran it rich.. pinched rings

 

What AFR do you shoot for when dialing in the nitrous?

 

12.5 - 12.8 for most
Ours liked 13.0

 

I agree with ATV..It was probably rich with too much timing = Boom!

 

turns out one of the injectors (stock injectors resized to 38lbs) was "bad." Not sure where I had this injector as we didn't think to keep track when taking the motor out.

It is possible. Sometimes pressure was too high for the nitrous solenoid to open and it would have gone very rich.

I haven't sprayed the car in over 10k miles, but I was experiencing blowby issues back then too, just not obvious. When I had the heads/cam done by a shop, they said the pistons looked good, but maybe they didn't really take a good look?
you search the forum and there's tons of posts saying that kind of blowby is normal so I thought nothing of it.

 

Did you have a dry system or a wet system?

 

Dry. At first I used a nozzle and let the maf figure it out - was having issues with that too

 

If it was dry and the solenoid never opened, then the maf never saw nitrous and adjusted. What was your air/fuel ratio on motor?

 

i had a thing from a defunct vendor that added fuel. before that i had just sprayed through the maf. afr on motor was ranging from 12.6 to 13.

 

Ohhh I know what you're talking about. That could very well have made it run rich.

 

injectors

i just got the injector service report and they did mark the injectors before sending them out. at 3 bar, #7 had a less than decent spray pattern and was only flowing 63.5ml whereas the others were flowing around 84.5ml.


also.. it looks like a small chunk of the intermediate piston ring is embedded onto the top of the piston