I just wanted to see if there's consensus on what is the main culprit of the following carnage. My tuner believes its a fuel delivery problem, most likely an injector that failed. Whatever it was, a hole like that requires sustained exposure to very high temperatures. Also note the hole is on the intake side, where temperatures should be lower. I have two thesis: 1. The injector feeding the cylinder failed, causing the ensuing carnage in a single, catastrophic event. 2. Detonation occurred a period of time prior to engine failure, which caused a fractured piston crown. The damaged crown then generated a local hotspot that "gradually" melted the cylinder wall.
I based my second thesis on the behavior of the engine prior to the event. Failure occurred after taking the car to be retuned, on the street after about 6-7 dyno pulls. The tuner noticed what could be described as a "power cut" when boosting more than 11 psi so the engine was left at this boost level. The cause of this cut could not be determined from the telemetry provided by the AEM EMS (according to tuner). The tune was performed in an ultra-conservative manner with 11:1 AFR and safe timing.

I ask the gurus for some guidance, as I will be sleeving/building the engine and don't want this to happen again.

The injectors are currently being tested.

Bone stock F20c.
AEM EMS
AEM boost controller, boost solenoid.
RC 750cc injectors.
Walbro 255hp pump.
Aeromotive FPR.
93 pump gas
Precision sc61 turbo.

 

Post the fuel and timing maps. Saying they're "ultra conservative" is hard to believe with damage like that.

 

my guess is way too much timing. too often people mistake conservative timing for what is actually aggressive timing. pulling over a degree per psi of boost is ulra conservative. fwiw.

 

Rc's r the cause


Don't be so quick to blame the injector.
RacerXI

 

I'd say way too agressive of timing. Your timing should be around 28 deg before boost starts coming in and when boost starts coming in, timing starts to drop to about 10 deg at your 11 psi peak boost hit. Then it will gradually go back up as rpm climbs and should be maxed at about 18-20 deg by around 8000 rpm and hold there to redline. This is just a basic way to do it, but if it's not in this general area, you were experiencing detonation.

Also, if an injector was beginning to fail, your tuner would have had to start adding fuel to keep the AF's in check and he should have known at that time that something wasnt right.

 

I'd like to see the timing map also.

 

Anything can happen, but that doesn't look like it happened all at once. That piston looks like its seen significant detonation for an extended period of time. Me thinks i'd be tuner shopping if I were you. Ditching the Rc's may not be a bad plan as well. Sorry for the trouble's, good luck with the rebuild.

 

Wow that piston saw a lot of heat. How do other cylinders look? If it had a bad flowing injector right from the start the tuner would not have necessarily known it was not flowing as much. I would get them flow tested to see how they compare.

 

Seriously? Stop spreading misinformation. While RCs aren't the best, they work fine, and I highly doubt they caused this.

Definitely looks like too much timing. +over9000 for the timing map to be posted.

 

+1 on what everyone else said, and I also noticed serious scuffing on the other cylinder in the picture. I'm guessing this motor saw A LOT of heat before it completely lost compression. MRGSR had a similar issue with his car a couple years ago and had similar motor damage. I'd be curious to see what becomes of this, good luck.