setup is h23 fully built, rods, pistons and sleeved with turbonetics kit, tuned on hondata s200. after a few runs on the dyno, we were at 335 whp at 14 psi. we raised the boost a bit more to 17 psi and boom, big cloud of smoke out of the back so we shut it down. after tearing the head off we discovered this




from the looks of the pistons, what could have happened?

 

the tune was off

 

are the pistons salvageable?

 

i see one i might reuse...the one on the far left looks like complete trash...i imagine your bore isnt looking to good so you will probably need new oversized pistons anyway

 

so does anybody else say it was the tune? any other possible causes?

 

can't see the pics, but im guessing that they are melted on the edges if the tune was off and running too lean.

 

here are some more pictures

 

im being told in another thread it may have been P2W clearence?

 

what was the gap? Also did u have a oil pressure guage? if so, what oil pressure were u seeing?

 

could have been a combination of tight P2W clearances, and maybe pushing it a bit much with ignition, etc....

seems like they over-expanded and ate themselves

 

My thoughts exactly...

 

that is exactlly what it looks like. don't ask me how I know.

 

they were not clearanced properly for the application/tune you were using them for, thats going to be the 99% correct answer most likely.

 

do you guys think this is something i should fight the machine shop for? what type of info could i gather up to build a case here?

 

Did you sign a waiver? If you did then you are SOL...

 

i am going to play devils advocate, because everyone is so quick to put the blame elsewhere. im not saying hte o.p. is right or wrong. it just gets to me when people look to put the blame on someone else.

many factors could be the reason.
my first engine i built a long time ago, i had an issue with fueling, it had an fmu with a chipped ecu. (didnt know better then)
my pistons got ate up like that because it was running way too rich, the fuel was washing off the oil. causing it to wear like that.

how was the car running on the dyno?

 

the car ran like a champ! im just looking for some answers as to how i would diagnose what happened?? the tuner is a seasoned veteran and authorized hondata dealer/tuner. im hesitant to put any blame on him. we were eyeing the data logs while he was tuning it and it would stay at a steady 12.1-12.7 and at times drop to around 11.5. the only mistake i would guess we didnt do is measure the bore sizes ourselves but you would assume a machine shop would do this multiple times, maybe even provide a sheet of their measurements to the customer after boreing the block. fuel pressure was at 55 and this was with brand new precision 760's and hondata s200 so proper fuel management was there.

 

i understand you looking for answers, and didnt want to start an arguement. working in this field for as long as i have, everyone is looking for an out.

if your machine shop is a decent business, tlaking to them would be a good step. if the afr's were spot on, p to w clearance would be an issue id look at. where did the piston that has no dammage or little dammage come from? where was the timing? did you have sufficient octane? read the plugs after pulls?

 

well this motor took roughly a year and some change to build and all measures were taking to avoid this from happening, no corners cut. as you can imagine, some answers are needed. well i believe the timing was roughly (IIRC) around 20* but im not 100%. i think the clean piston was #3, and this was ran on 93 octane. the plugs were not pulled after every run.

 

machine shop is only going to set it to what you tell them too, or set it to something that is going to be close to what you would need. There is no way for them to tell what the hell you are going to do with it once it leaves their shop.

 

Have a different machine shop measure the pistons and cylinders. The sides of the sleeves should be measurable, as will the good piston. The bad pistons may be measurable, at least 45 degrees from the pin location. That should get you close enough to see what P2W was.

If they were high-silicon (SRP) it should have been >.040", or >.035" for regular forged slugs. Most piston makers spec the P2W too tight, since they're not used to motors making the specific output Hondas do with "just" 17psi. I've seen a fresh sbc350 run w/o coolant for a few mins, pistons started looking like that when it they over-expanded.

The other thing is 2-stroke motors that run lean tend to melt like that. I'm curious if 1 injector is less clogged or flows more or something. If 3 cylinders were 13:1 and one was 11:1, the average would be 12.5:1...just another idea.

 

they were JE pistons and they were set to JE Specs. the injectors were brand new out of the box but we'll double check the spray pattern of all 4 to be on the safe side. we're also going to try and measure the sleeves and pistons asap. do you think the scaring of the walls would change the size of the sleeves much? or the pistons for that matter.

 

when you start the car you let it warm up to full temp before driving

 

Im not saying i know for sure the problem but it could be any number of things. I had a stock gsr that i turbo'd and my buddy tuned it ran freakin hard on 6lb's with a topmount and a gt30 fuel was good wideband was reading good and then the 3rd pass after it was tuned it melted a piston. The only thing we can figure is we were not pulling enough timing.
How much timing were you running, and pulling per pound of boost? Were you pulling any degree's up in the top end say past 6k? My buddy that tunes my stuff always likes to pull an extra degree or 2 up top just to be safe, and thats on top of the 1 degree he pulls per pound.
Thats just my 2 cents hope ya figure it out good luck

 

yea thats pretty conservative...1*/lb. mines close to or about .75*/lb retard. forged parts take a lot of abuse and fatigue after a while. p2w clearence would be my reasoning. like my setup je told me 0.035", took it for what its worth and a went a little looser and did 0.045" for my power level. you should always run on a little on the loose side anyways. expansion will be the last of your worries.