Broken Rings on a 06 5.9

[TCDiesel]

Couple timing with to much Duration at High pressure wets down the cylinder walls. or the spray pattern gets out of the bowl destroys the piston.

 

[Wayne M.]

Too much timing is the usual problem. That drives cylinder pressure way up with fueling mods.

There is no way for a diesel to experience pre ignition and set up a condition similar to gas engine detonation/pre ignition and break rings and such? Isn't that what pilot injection is in a controlled manor?

 

[cerberusiam]

There is no way for a diesel to experience pre ignition and set up a condition similar to gas engine detonation/pre ignition and break rings and such? Isn't that what pilot injection is in a controlled manor?

Combustion dwell time in the cylinder, which is a function of timing and duration. Detonation in a diesel doesn't happen, the fuel won't vaporize and pre-ignite, The typical diesel rattle is a spike of pressures from a large injection even. The pilot injection is limited fuel then the main event is more but by design the timing is retarded so cylinder pressures do not spike as high. Advance the timing and in-cylinder condition moves closer to stoich which raise the max pressures. By design modern diesels are stoich rich for emissions reasons, changing the timing, pressure, and duration changes the results in-cylinder.

 

[Wayne M.]

changing the timing, pressure, and duration changes the results in-cylinder.

Understood, and of course you're within stock timing or a mild tune. But what about a tune gone bad? Not implying that's what happened here, but what if cylinder pressure got out of control under a heavy load and high cylinder temps? I'm not a diesel as much as a gasoline engine tuner, so my thinking defaults there. High temps can cause ring butting/ seizure and things get worse from there.

 

[cerberusiam]

High temps are natural for a diesel, much more so than a gas engine. The rings are engineered and gapped accordingly. It could be a mismatch in the tune, a mismatch in the fueling tables, a failure in the injector to perform EXCATLY as expected, or even a random set of parameters that all come together at rare times. Once you go beyond the stock tune all bets are off, once there are enough miles on the engine all bets are off. there are so many things it is hard to point to one and say exactly that was it, more of a trend based on information gleaned about tuning and setup is all we have.

 

[Wayne M.]

I totally agree.

 

[B.G. Smith]

I broke the top ring on several cylinders of a 70 Dodge Charger once when I over- revved it a little. It had a ridge at the top of the cylinders though and the top rings must have hit the ridge. I doubt that a Cummins would have a ridge with that few miles though. bg

 

[bigceltic]

So did we ever come up with a solid conclusion on what happened to the Gentlemans engine?

John,

Did you ever come up with a root cause for the failure?

 

[AH64ID]

Nothing, and we never will at this point.

Guessing faulty rings, but no real proof. Nothing else indicated it was an issue.

Crappy tuning on 04.5-07's almost always leads to piston failure due to the weak design of the piston. His pistons were pristene, in terms of tuning effects. 1/6 had a bit of carbon on them