ok my setup was b20z stock,stock LS head,to4b 60trim turbo,450cc injectors,walbro 255,street tuned on crome by me on 11psi only running 15* of timing at 11psi safe cuz of thin walls. Did a injectors lean out or did it dention??? but the injector is fireing cuz i drove the car home (2miles) after this happen.


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sure looks like detonation to me, are you still running the factory MAP sensor with chrome? If so you are pretty close to its limit and could have caused you to go lean.

 

Leaned out and detonated, On the down stroke who knows

 

post pics of the plug...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by THEDirtyDseriesWOOT &raquo;</TD></TR><TR><TD CLASS="quote">post pics of the plug...</TD></TR></TABLE>

 

Too much timing or went lean. Have your injectors tested just incase

 

also what was the condition/mileage of the motor before?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Brain3208 &raquo;</TD></TR><TR><TD CLASS="quote">sure looks like detonation to me, are you still running the factory MAP sensor with chrome? If so you are pretty close to its limit and could have caused you to go lean.

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Map sensor not an issue, i ran the stock sensor at 15 psi, for over a year, and the motor is still running in my daily driver NA now. It's just harder to get a perfect tune, but wide open throttle is still easily doable.

Was that the only piston showing this wear/damage? If so i'd be looking at the injectors.

 

too much heat....piston expanded and went oval. thats what cause the scarring. then the friction/heat cause the ring lands to break. you either had a shitty tune or you cranked up the boost after you got tuned.......or something bad happened causing you tune to not matter anymore

 

ring lands crack because of realy high pressure on the compression ring and high temp that softens the ring land causing it to crack.
either you had some serious boost creep, or detonation (caused by a/f or ignition). from what you situation I doubt it was preignition...unless you were pushing it to the limit pegging the limiter and what not. the scarring on the cylinder wall is from the loss of seal between the compression ring and the oil ring due to the cracked ring land. it allows fuel to "wash" the cylinder walls of lubrication and the temps jump allowing the pistons to expand more than normal and fubaring your pistons/cylinder walls.
detonation normaly cause all its damage near the edges of the piston also. so Im gonna say this engine probaly had a decent amount of miles on it and the compression was probaly a little low on this cylinder causing your lean situiation.

 

this motor had about 30,000 on it and we where doing highway pulls and the frist race was good then we did one right after then it did this and yes it bangs off the limiter 2nd,3rd and i always watch my wideband when i race and it was 11.5 all the way and the timing was very safe so i think it was injector lean out.

 

i saw the thread name and then the user name and stopped reaeding

But honesrtly, i would say clogged injector b/c its local to that one piston.

 

what kind of injectors are you running?