Wow, there'* someone with experience in blowing pistons.

So the part throttle 12* of KR that I see must not be too good. :(

What did you do to get rid of the knock......or, judging from the number of failures, I guess you didn't. :?

lol.. yeah issue was fixed.. to bad it took me out for an entire season. A couple good passes tho..11.6 was the best :(

My direct issue was maxing out the MAF...and it even slipped by some of the "big dawgs". 18lbs of boost, at 12200 maf=BOOM lol

But issues similar to the poster, I have seen a few times while pushing the limits.

I've ran every setup available....and pushed them all

Its never good to see that much KR boosted...but it could from other issues. But that would a be a different thread Part throttle...I would guess its a TQ management issue.

Did you pop the same piston every time? if so, which piston was it? Was it even the same bank of pistons every time? If you blew 5 engines and five times it was #4 cyl that had the problem, wouldn;t you suspect something was not right, besides the tune or lack thereof?

2 of the 5 were the same piston(*)(1-3-4). 1,3,5,4 once, and 1-3 once.. Everything is my setup was brand new. We tried different everything, went thru the PCM line by line, went thru scans line by line, checked EVERYTHING3 times. new short block 3 times, replaced heads once, ect....and found nothing until IDD 2006.I also found I had a cracked LIM-build #4.
Tuning is the biggest factor, especially when pushing the limits, or doing "something new" like the twin charge setup.
2 times was just my dumarse wasn't smart enought to let off the gas... would've saved it for another day.
MAF was a HUGE contributor... not so in your case, from what I can see.
I have yet to have an issue since....

Mecahically the only thing I see as a possiblity, is the head is flexing and its allowing unmetered air into the cylinder. That just from the pics and how its blown out.

My last 2 pistons were on a different car...cam key broke and lost 2 pistons....car has since had zero issue 50kmiles later.

What did you find? And where was the LIM cracked? When I first ran this engine, I was having an issue with #2 and #6 injectors sucking a little air, I repositioned the fuel rail and it fixed it. Under boost tho, it would be a boost leak, not a vac leak.

I certainly hope that after all that he has a GTP that'* faster than 13 seconds.

What size pulley did you have on when you outflowed the MAF :?:

That sounds like a possibility to me.

If you have a boost leak on #2 and #6, you're losing a certain volume of air that has already been metered by the MAF and would have normally made its way into those cylinders. Based on the MAF reading the injectors send a certain amount of fuel into the cylinders, but since you're losing some of the oxygen volume the O2 sensor sees what it thinks is a rich condition after combustion. Since you were using a wideband on one bank at a time, you were getting a false rich indication on the 2-4-6 bank and pulling fuel on all three of those cylinders at a time. This would result in the #2 and #6 cylinders being closer to stoichiometric AFR (because they had a lower volume of oxygen due to the leak), while the #4 would be getting leaner and leaner. Make sense?

Add all of it up and it equals a popped #4 every time, no matter which way you slice it.

That'* my theory based on your last post

Amazing observation! Though I really think I fixed the vac leaks at 2 and 6 long before any of this happened. I was smoke-testing the engine for leaks when I first put it together b/c the intercooler core was leaking. That'* when I identified a bunch of vac leaks people probably always have (having the IAC control idle isn't always a good thing...) Once I repositioned the injector rail, I had no more leaks at the injectors, but I will check again when it goes back together.

Well it was worth a shot

I hope you track this down, Jeff. I look forward to seeing the car at full power in the near future. Let us know what you find.

Yes, that theory makes a lot of sense. Balanced flow seems to be very critical for these engines.
Although it would be incredibly expensive, a much better way to go would be separate O2 sensing and control of each individual cylinder.

I see now why precision CNC'd runner machining is very desirable.