[MVF39C]

MNN begging for attention attention.

 

[jsmite04]

A good friend of mine had a rod fail at 8500 rpm in pretty much the exact same place as this one. Rod journal and bearing was fine, as the big end was still intact.

Being NA, there was no pressure entering the chamber to push the piston back down the bore, but the dome, chamber and valves were beat beat up pretty good. The intake valve was bent pretty bad, but didn't break.

I believe Randy's analysis is extremely plausible that the rod failed first.

 

[DRIVER456]

What does it matter what broke first,It broke! And is going to cost him the same to fix it no matter what broke first.

 

[edcmat-l1]

OP ain't never built a bicycle. FACT!

 

[edcmat-l1]

My failure analysis says another thread fail by the OP!!!

 

[edcmat-l1]

100% agree. There’s way too much piston damage to have happened on one stroke, and as soon as the rod broke the piston would have stopped.

This is where dumb dumb's lack of experience shows.

In this case, intake pressure would have continued to push the piston down into the crank and rod causing it to continue to beat itself to death.

DBT hasn't ever built anything, has never done any real failure analysis, etc. Doesn't know the difference between the failure in a NA engine versus FI.

 

[Topfun99]

What does it matter what broke first,It broke! And is going to cost him the same to fix it no matter what broke first.

How about this? Understanding what broke is the first step towards making improvements to prevent it from happening again.

 

[Topfun99]

My failure analysis says another thread fail by the OP!!!

Well, if you really think the valve failed first you either did not read my posts or did not understand the physics involved.

 

[edcmat-l1]

Well, if you really think the valve failed first you either did not read my posts or did not understand the physics involved.

Perhaps you didn't read my other post??

It almost impossible to determine which came first from the pictures. The argument could be made either way. But, the continued movement of the piston, in your application, could 100% happen AFTER the rod failure.

Yes, I have done real "forensic" mechanical failure analysis and I've represented people, in court, as an expert witness.

 

[VinnyVette9340]

Well, if you really think the valve failed first you either did not read my posts or did not understand the physics involved.

If you had it all figured out. Why did you create the thread asking for opinions?

 

[DeepBrainThrombosis]

Well, if you really think the valve failed first you either did not read my posts or did not understand the physics involved.

More people think the valve failed first, by posts and by poll. Sorry bud, you and warp got this one wrong. Your theory requires too many holes in the swiss cheese to line up precisely just so vs. the valve breaking first. At some point you just have to accept that.

 

[VinnyVette9340]

This is where dumb dumb's lack of experience shows.

In this case, intake pressure would have continued to push the piston down into the crank and rod causing it to continue to beat itself to death.

DBT hasn't ever built anything, has never done any real failure analysis, etc. Doesn't know the difference between the failure in a NA engine versus FI.

There is no intake pressure in a NA application. There is a negative pressure drop “vacuum” created by the piston drawing the intake charge on the downstroke. The piston would have to remain connected to the crankshaft to create an intake draw. There would be no compression in the combustion chamber due to the broken valve head. If the piston was still connected to the rod with the valve being broken air would be forced back into the intake manifold when the piston is on the upstroke.

 

[DeepBrainThrombosis]

This is where dumb dumb's lack of experience shows.

In this case, intake pressure would have continued to push the piston down into the crank and rod causing it to continue to beat itself to death.

DBT hasn't ever built anything, has never done any real failure analysis, etc. Doesn't know the difference between the failure in a NA engine versus FI.

Yes, the intake pressure absolutely would have pushed it down into the crank and broken rod causing it to beat itself to death, I agree 100% on that. What it would NOT have done is bounced up and down the cylinder 50+ times causing all the damage up top that we see. Every one of those dents was caused by the piston hitting the combustion chamber hard with the broken piece of valve pinched in between. There are dozens and dozens of them. That means dozens and dozens of energetic hits of the combustion chamber with a broken valve pinched between. That doesn’t happen with a connecting rod driving it up there.

In time when you put the angry leprechaun attitude away and you really step back and make all the pieces fit, you will see that they don’t with the “rod broke first” theory. They DO with the valve breaking first.

 

[edcmat-l1]

There is no intake pressure in a NA application. There is a negative pressure drop “vacuum” created by the piston drawing the intake charge on the downstroke. The piston would have to remain connected to the crankshaft to create an intake draw. There would be no compression in the combustion chamber due to the broken valve head. If the piston was still connected to the rod with the valve being broken air would be forced back into the intake manifold when the piston is on the upstroke.

Why are you quoting me as if you need to explain this to me???

 

[VinnyVette9340]

Why are you quoting me as if you need to explain this to me???

“In this case, intake pressure would have continued to push the piston down into the crank and rod causing it to continue to beat itself to death.”

Because you’re wrong.

 

[edcmat-l1]

Yes, the intake pressure absolutely would have pushed it down into the crank and broken rod causing it to beat itself to death, I agree 100% on that. What it would NOT have done is bounced up and down the cylinder 50+ times causing all the damage up top that we see. Every one of those dents was caused by the piston hitting the combustion chamber hard with the broken piece of valve pinched in between. There are dozens and dozens of them. That means dozens and dozens of energetic hits of the combustion chamber with a broken valve pinched between. That doesn’t happen with a connecting rod driving it up there.

In time when you put the angry leprechaun attitude away and you really step back and make all the pieces fit, you will see that they don’t with the “rod broke first” theory. They DO with the valve breaking first.

You're a fool and a poser. You have nothing to back up anything you say here. You're the new resident fool on YB. As bad as NAYNAY.

 

[DeepBrainThrombosis]

There is no intake pressure in a NA application. There is a negative pressure drop “vacuum” created by the piston drawing the intake charge on the downstroke. The piston would have to remain connected to the crankshaft to create an intake draw. There would be no compression in the combustion chamber due to the broken valve head. If the piston was still connected to the rod with the valve being broken air would be forced back into the intake manifold when the piston is on the upstroke.

It was under boost when the failure occurred.

 

[edcmat-l1]

“In this case, intake pressure would have continued to push the piston down into the crank and rod causing it to continue to beat itself to death.”

Because you’re wrong.

Pretty sure this is a turbo motor dude.

 

[DeepBrainThrombosis]

You're a fool and a poser. You have nothing to back up anything you say here. You're the new resident fool on YB. As bad as NAYNAY.

Starting the day still drunk from the night before isn’t a good look, FYI. Might want to consider changing your ways, it’s got you not only angry, but completely unable to think logically.

 

[VinnyVette9340]

It was under boost when the failure occurred.

I don’t see anything in his post that mentions boost. I’ll take your word for it.