How? Why? Lol

[robmustang201528]

Not my car. One of my friends has a 2011 GT. He put a 2015 short block in it, with his 11 heads, car has a whipple making 12 to maybe 13lbs at times on pump gas. Car was running for 2 to 3 years with this setup until the top of the piston broke. I've never seen anything like that. His car made 690hp around 680tq. How? What caused that to happen? He said he's just going to replace the piston.

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[Dusten]

Detonation. There's melter aluminum. All over in that picture. It cracked the top of the Piston.

 

[robmustang201528]

Detonation. There's melter aluminum. All over in that picture. It cracked the top of the Piston.

Tune?

 

[EFI]

Tune?

Most likely not tune if you said he was running this same setup for 3 years. If it was a bad tune, it would have blown up 3 years ago.

That's probably bad gas, hot engine/intake or just pure bad luck. Most likely a combination of all 3.

And the way that piston broke is pretty much textbook when it comes to stock pistons, stock compression, low octane gas (eg. not E85 or racegas) and 13psi of boost. The ringlands are the weakest part of the piston, especially when exposed to much higher cylinder pressure from boost and/or detonation.

 

[ugstang17]

Which cylinder was it OP?

 

[Crackerjack17]

That is heat with likely ring lands butting over time weakening the metal and a little detonation here and there sprinkled in.

 

[robmustang201528]

His car used to smoke sometimes after start up. I also noticed smoke coming out of his exhaust when riding behind him on a decele

 

[robmustang201528]

Which cylinder was it OP?

I want to say 6 or 7

 

[302@12psi]

Just replacing the piston? Where does he think the pieces of the piston went?

 

[ugstang17]

If the cylinder was actually #8 this was a problem on early setups as tuners were getting overly aggressive with timing on big N/A builds and high boost FI setups. It's been years now, but as I recall -- someone correct me if I am wrong -- it was a head flow issue with regard to how coolant was routed. Cylinder 8 being the last in line of flow got the least heat removed from it. MMR designed a cooling mod that provided better flow utilizing the freeze plugs on the front of each head. This kit supposedly helped with this problem and allowed engines to perform better under modified conditions. Having had 3 Coyote boosted setups I have never had this issue. But then again I never pushed 690 RWHP out of one either. 631 has been my max on this car and 568 was the max on the 13.

 

[engineermike]

I’ve done quite a bit of benchmarking and have come to realize that if you went oem levels of reliability then you have to stay within oem compression/boost/bmep limits. I can’t find any instances where an oem has run more than 9.5/1 compression with port injection and boost or 10.5/1 with direct injection and boost. This is not because they can’t, but because they have to be reliable in all scenarios of bad gas, high temps, low temps, clogged fuel filters, bad injectors, clogged cats, and combinations of the above. When we run boost on 11 or 12/1 compression, if anything isn’t quite right it’s liable to let you know quickly and expensively.

 

[robmustang201528]

Just replacing the piston? Where does he think the pieces of the piston went?

Bro!!! Smh I said the same thing smh. Idk

 

[gimmie11s]

Very common. Pistons are weak link on stock motors.

factory ring gaps set too tight and ring lands crack causing what you see above.

 

[robmustang201528]

It's funny, you read and hear stories about people on a stock block making 700 800hp+ without any issues on 93. I guess the question is how long will it last. My car is making 713 on 93 with the jlt inlet pipe on. It made more without the cold air pipe on. We added a gallon of 110 fuel to keep it safe when it was on the dyno. It hit 13lbs.(vortech V7JT blower.) It's been cold out here and I saw 13lbs the other night. I think I'm going to start running 100 octane during the winter months just to be save.

 

[engineermike]

Very common. Pistons are weak link on stock motors.

factory ring gaps set too tight and ring lands crack causing what you see above.

The cool thing is that what now happens at 700 rwhp used to happen at 350 rwhp (25 years ago).

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