Anyone seen a gen3 piston failure like this?

[engineermike]

Are the aftermarket piston and ring suppliers using the same mindset? I believe they also use a low ring tension.

Not that I have seen, but I trust Ford engineering over the aftermarket. Even the 2018 cobra jet runs tighter ring gaps than the aftermarket generally recommends. I pick something in between the gt500 and cobra jet specs to use. The idea behind wide ring gaps is to prevent ring gap butting and binding in the bore which leads to broken ring lands, but those types of failures are surprisingly uncommon in coyote and gt500. The gt500 spec is .008-.012 top and .014-.022 2nd and those motors withstand tons of boost and power.

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[engineermike]

Yeah, someone probably did something wrong (and it wasn't ford) but that doesn't matter anymore.

I guess this is where we disagree. I believe it does matter because something can be learned from failures to help prevent them in the future.

 

[SheepDog]

............ you boosted a NA motor with hyper-eutectic pistons.

no this is not a common failure mode, even in SC applications, however, it is FAR more common once you start forcing pressurized air into those cylinders because A. the part failure odds go up and B. the tune now becomes very important.

you boosted a motor and it let go. no mystery here.

Yeah, someone probably did something wrong (and it wasn't ford) but that doesn't matter anymore.

I think you might be missing the point of the thread. The question was, has anyone seen a failure in this manner - not "why did my piston fail". The connecting rod, yanking itself out of the piston is not a common failure point, boosted or not. Failures that are typical with excessive cylinder pressure include blown head gaskets, broken ring lands, melted pistons, spun bearings, bent connecting rods. Failure of the type they had - I guarantee is not from tuning

 

[Oakley]

I think you might be missing the point of the thread. The question was, has anyone seen a failure in this manner - not "why did my piston fail". The connecting rod, yanking itself out of the piston is not a common failure point, boosted or not. Failures that are typical with excessive cylinder pressure include blown head gaskets, broken ring lands, melted pistons, spun bearings, bent connecting rods. Failure of the type they had - I guarantee is not from tuning

Maybe I am missing the point, I don't see the mystery.

To me it looks like the piston cracked allowing for the wrist pin to be yanked out from the lobes that would otherwise hold it in place.

my theory:

step 1. red is the first split.

step 2. blue is where after the split the piston halves twisted and fractured more.

step 3. green is where the lobs got ripped off after the piston halves could rotate more than the lobs could bear.

all of that probably happened in less than a second.

a forged piston wouldn't do this, hypereutectic (super fancy cast pistons) are really great but once they crack its donezo.

 

[SheepDog]

Maybe I am missing the point, I don't see the mystery.

To me it looks like the piston cracked allowing for the wrist pin to be yanked out from the lobes that would otherwise hold it in place.

my theory:

step 1. red is the first split.

step 2. blue is where after the split the piston halves twisted and fractured more.

step 3. green is where the lobs got ripped off after the piston halves could rotate more than the lobs could bear.

all of that probably happened in less than a second.

a forged piston wouldn't do this, hypereutectic (super fancy cast pistons) are really great but once they crack its donezo.

I think the concern here was that- a cracked piston is generally caused by detonation. Yes, a forged piston is a lot more robust, and less likely to crack, but they were not experiencing knock during this event (evident in the log). So, they wanted to see if anyone else had a failure in this manner, and if there was a determining factor. Very well could just be a manufacturing defect in the top of the piston, and the extra boost and timing found that weak spot.

Many other stock Coyotes hold together at this power level, but obviously the expectation of OEM lifespan should not be considered when subjecting the engine to forces well outside of it's design parameters. Honestly, the fact that a Coyote can tolerate this behavior at all is a testament to the design and quality of parts that Ford uses.

 

[Autopart101]

If the prevailing failure theory is correct, then it's more of a statistical thing. Even stock NA pistons fail, so any additional stress will increase the failure rate. We've seen 1050 rwhp from a PD blower on stock pistons hold for at least a few dyno pulls....could last forever...could fail on the next hit, but for sure the chances are higher than with 400 rwhp. That said, I've heard it stated that 850 rwhp is the sweet spot for a stock coyote and 10r80. You can generally make on live a long time at that power level.



The owner is going wtih Mahle 10.4/1 pistons and GT500 rods. It's an interesting combination, but should be very strong and more forgiving.

I'm friends with a guy who retired as an engine calibrator from a large-scale performance engine manufacturer. He thinks we're all crazy for running the compression, timing, and boost that we do. They got engines to hold up long-term at high power levels by running very low compression and timing even if knock was not encountered.

I think 800-850RWHP is the sweet spot for 10R80 cars. My Trans started slipping over 850.

 

[OldbutNew]

Maybe I am missing the point, I don't see the mystery.

BOOM! Literally and figuratively!!

 

[Oakley]

BOOM! Literally and figuratively!!

this is what i try to communicate to guys modding these engines with boost.
all it takes is one defect or bug or lag in a tune that's been tinkered with and that can kill your motor. it also doesn't help that people treat tuners like they make power and get them to squeeze every last pony out of a setup not realizing the more you squeeze the less room you leave for error.

this is why i bought a car with more power than i even care to have and have only done suspension mods to get that stuff dialed in. im boring but my car is faster than 99% of whatever is on the road so who gives a shit?

 

[robvas]

im boring but my car is faster than 99% of whatever is on the road so who gives a shit?

That's different than being faster than 99% of sports cars on the road

 

[SheepDog]

but my car is faster than 99% of whatever is on the road

definitely not. Unless you have 1000 HP. Most electric cars on the road will smoke a stock Mustang. Any BMW with a 6 cylinder or 8 cylinder, Any Audi with a 5, 6 , or 8 cylinder, plenty of tuned 4 cylinder cars, etc. My tuned Powerboost F150 beats up stock Mustangs, at this altitude anyway.

 

[Oakley]

definitely not. Unless you have 1000 HP. Most electric cars on the road will smoke a stock Mustang. Any BMW with a 6 cylinder or 8 cylinder, Any Audi with a 5, 6 , or 8 cylinder, plenty of tuned 4 cylinder cars, etc. My tuned Powerboost F150 beats up stock Mustangs, at this altitude anyway.

horse shit.

 

[SheepDog]

horse shit.

ok.

Why do you think so many people in here go to the trouble of adding forced induction to these cars?
1- because the Coyote is very receptive to FI
2- because the PCM is incredibly capable
3- because these cars are slow AF in stock form.

 

[cbrtrx]

ok.

Why do you think so many people in here go to the trouble of adding forced induction to these cars?
1- because the Coyote is very receptive to FI
2- because these cars are slow AF in stock form.

I'm guessing Oakley is being sarcastic and joking. He can't be serious.

 

[SheepDog]

I'm guessing Oakley is being sarcastic and joking. He can't be serious.

Or, he thinks his car really is fast. I'll assume sarcasm for the moment

 

[Robottrainer]

ok.

Why do you think so many people in here go to the trouble of adding forced induction to these cars?
1- because the Coyote is very receptive to FI
2- because the PCM is incredibly capable
3- because these cars are slow AF in stock form.

Thats why I like the Roush set up. For my usage on the street, its more than capable. The only areas I touched was the trans, changed the throttle response and active exhaust. The rest I didnt touch. The only thing I anticipate a problem with is the cats. I have a back up plan for that.

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