What caused this piston damage?

[nycstev]

Here are some photos a friend of mine sent showing 6.1 hemi with damage on ALL the pistons. This is from an 09 Challenger (Paxton) with less than 1000 miles!!
Obviously you can see broken lands and how they " shotpeened " the piston and combustion surface area. BUT he is claiming that this happened from DETONATION in all the pistons even though he had perfect AFR's all across the board with now signs of detonation!! My question is how is that possible? He also claims rthats the reason for piston failure in our trucks and NOT defective pistons.

What do you think?

 

[TREKER]

There had to be tons of shit flying around in there. The next head has the same damage. Detonation causing pitting like that? :dontknow: I'm no expert but that looks like someone had alot of schtuff in there. Do the valves look as bad?

 

[DevilDawg3097]

thats not from detonation, somthing, maybe valve's its hard to tell with those picture or something broke off and was goin through the motor. Those arent just little scratches those look like deep gouges. I have seen that on some diesels I have rebuilt, rings and little pieces of the piston get caught up in the combustion chamber.

 

[Wifey]

There had to be tons of shit flying around in there. The next head has the same damage. Detonation causing pitting like that? :dontknow: I'm no expert but that looks like someone had alot of schtuff in there. Do the valves look as bad?

Stock Pistons and FI = Boom

 

[nycstev]

thats not from detonation, somthing, maybe valve's its hard to tell with those picture or something broke off and was goin through the motor. Those arent just little scratches those look like deep gouges. I have seen that on some diesels I have rebuilt, rings and little pieces of the piston get caught up in the combustion chamber.

If you look at the pic you can see the broken land . This is what broke off. The question is how can you have detonation with no audible sounds of knocking and good AFR's from a dyno run?

 

[DevilDawg3097]

If you look at the pic you can see the broken land . This is what broke off. The question is how can you have detonation with no audible sounds of knocking and good AFR's from a dyno run?[/QUOT hes looking for something else to blame it on then the paxton. I saw the lands, are all the piston like that one? if so just like wifey said stock shit with FI ends up like that. IF all his piston look the same then now you know what caused it the pieces of the piston inside the combustion chamber ie right on top with nowhere to go. what boost was he running?

 

[Wifey]

If you look at the pic you can see the broken land . This is what broke off. The question is how can you have detonation with no audible sounds of knocking and good AFR's from a dyno run?

There is no need for detention being the reason for failure, the pistons design is Junk ( cast) They just will not take the extra stress from FI. Also the ring gap is criticall on FI engines due to thermal expansion, the rings need more gap even with forged pistons.

 

[TREKER]

He must have been running that thing with a tone of banging going on for a while.

 

[Wifey]

He must have been running that thing with a tone of banging going on for a while.

That whole mess could have happened in a nano second, and at 5-6000 rpm most of the damage probably happened during engine shut down.I see no carbon or deposits in the "peened" areas of the head or piston.
just a cheap azz piston failure, and the valves should be toast also

 

[rottenronnie]

The new Challengers must be tricky to tune, they seem to make it harder every year to work with the new stuff..
Detonation damage, initially, then all the junk flying around did the rest of the artwork, I would bet.
As far as cast vs. heat treated hypereutectic vs. forged goes, they ALL lose if things get this bad!
How do the plugs and head gaskets look?
Poor thing....'never had a chance....

 

[nycstev]

9 responses and noone understood my question. How can you have detonation with perfect AFR's and no signs of detonation? He is saying this is what causes all FI engines to go.

 

[supercar1of1]

If you look at the pic you can see the broken land . This is what broke off. The question is how can you have detonation with no audible sounds of knocking and good AFR's from a dyno run?

If the rings over expand evenly (like they should, all else being equal) they would then seize in the cylinder wall more or less evenly, with no audible warning and produce the above result.

Just my theory.:dontknow:

.

 

[rottenronnie]

I'll offer one explanation:

I can no longer hear an engine ping.
Does the guy operating the dyno play in a rock band?

Audible ping starts at approx. 1750 degrees F. After that point, detonation can set in if the condition(s) causing it aren't corrected.

Good A/F doesn't guarantee an engine won't ping; but leaning toward rich is a safety measure however.
It is just that lean mixtures burn hotter and end up being closer to the 1750 degrees above. When cylinder pressures build due to f.i., the engine getting
"up on the cam", gear selection or what have you, the A/F AND TIMING better be close to optimum because a rise in pressure is also a rise in temperature. Throw in a few variables like fuel that is too low in octane, too high a static compression ratio, incorrect timing, INCORRECT TIMING COINCIDING WITH THE BOOST BEING APPLIED, vehicle weight, etc; problems can surface. Heat PLUS the shock produced by an erratic flame front can quite easily shatter a cast piston ring land and compress a forged one, killing any ring movement. The shock caused by detonation can also hammer rod bearings and even loosen bolts on harmonic balancers and flywheels.

 

[BigRed460]

Yall really dont get it, dodge does not make motors to handle boost. How simple is that? Boost = Boom, it's not rocket science. If you call and SRT engineer and ask if it's ok for you to put boost to a stock motor they will tell you no, replace the rods and pistions...

An auto maker that is in money trouble is not going to over build a motor, they are going to save every penny they can...


As for your question : The answer to what the exact cause is, IMHO it is HEAT; the cylnider walls expanded along with the rings ,and that in, turn broke the upper ring lands and they bounced around in the cylnider causeing the damage you see there. If it was on a dyno, then the pulls were being done way to close together...

 

[Wifey]

If the rings over expand evenly (like they should, all else being equal) they would then seize in the cylinder wall more or less evenly, with no audible warning and produce the above result.

Just my theory.:dontknow:

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BINGO we have a person with mechanical understanding:congrats: :congrats: :congrats: :congrats: :congrats: :congrats: :congrats: :congrats: :congrats: :congrats: :congrats: :congrats:

 

[nycstev]

I'll offer one explanation:

I can no longer hear an engine ping.
Does the guy operating the dyno play in a rock band?

Thanks. This makes the most sense. Since what he is telling me doesnt make
much sense either. In other words I didnt believe his explanation. I just wanted to see if anyone could substantiate his theory

 

[supercar1of1]

BINGO we have a person with mechanical understanding:congrats: :congrats: :congrats: :congrats: :congrats: :congrats: :congrats: :congrats: :congrats: :congrats: :congrats: :congrats:

Thanks, once upon a time(pre Defib) I had a couple functional brain cells.




.

 

[Wifey]

Thanks, once upon a time(pre Defib) I had a couple functional brain cells.




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Ya only need one to be ahead of this group :marchmellow: :marchmellow:

 

[nycstev]

As for your question : The answer to what the exact cause is, IMHO it is HEAT; the cylnider walls expanded along with the rings ,and that in, turn broke the upper ring lands and they bounced around in the cylnider causeing the damage you see there. If it was on a dyno, then the pulls were being done way to close together...

I agree . Fatigue failure. This guy is telling me its detonation and I don't buy that explanation. If you had that much detonation in all 8 cylinders you would be noticibly down on power. This Chally had only 700 miles on it! Obviously it didn't have time to reach fatigue failure in a conventional sense . I think it was WAY WAY over boosted so it just blew up.
This is the same person who is telling me my pistons failed from detonation.
I find it hard to buy. My AFRS were right on and the engine ran smooth as glass and pulled very strong with no signs of detonation.

 

[Marc T]

You guys sure know how to ruin a persons day!!