2011 piston failure diagnosis discussion w/pics

[VET-KLR]

It had seen 7700 RPMS on datalogs. I was also datalogging and working on get the thing to shift into 3rd gear at WOT properly. What it was doing and a few I've talked to think may have been the cause of the failure. The car would pull hard through 2nd gear, all power would go away like the car shut off, it would shift, and then all power would come back. This is an automatic car. The night it went completely the new tune I just loaded had just shifted properly into 3rd gear at WOT for the first time and it did hit hard.

The other weird thing that was never worked out by the previous tuner was another with a shutdown of power. Merging into traffic no less the car will just lose all power like it was turned off and then take off again. If you started giving it throttle slowly it would flash RPMs and go to idle moreless. Then the throttle did nothing for 2-3 seconds. Left me hanging in oncoming traffic more than once to the point I parked it. Working with Lund Racing to get it dialed in and then dyno tuned soon.

 

[r.barn]

It had seen 7700 RPMS on datalogs. I was also datalogging and working on get the thing to shift into 3rd gear at WOT properly. What it was doing and a few I've talked to think may have been the cause of the failure. The car would pull hard through 2nd gear, all power would go away like the car shut off, it would shift, and then all power would come back. This is an automatic car. The night it went completely the new tune I just loaded had just shifted properly into 3rd gear at WOT for the first time and it did hit hard.

The other weird thing that was never worked out by the previous tuner was another with a shutdown of power. Merging into traffic no less the car will just lose all power like it was turned off and then take off again. If you started giving it throttle slowly it would flash RPMs and go to idle moreless. Then the throttle did nothing for 2-3 seconds. Left me hanging in oncoming traffic more than once to the point I parked it. Working with Lund Racing to get it dialed in and then dyno tuned soon.

these automatics are very hard to tune properly. Many tuners had trouble with them when they first started putting PD blowers on these cars.

from your statement and the pictures I do not think you had detonation. I think you shock loaded the rotating assembly from hard shifting the transmission sending weird forces back through the rods and into the piston causing them to fail.

just my 02 cents

 

[19COBRA93]

Here is a 2011 block (running Boss pistons) that was making about 700rwh. This happened on the dyno during a "tune" session. Most the pistons showed a little scuffing and obvious signs of running lean, but all held up. The Moly had burned out of most of the rings as well. I'd consider this a weak link in the block, but this was caused by a bad tune. This was cylinder #3, there was a hairline crack in cylinder #7, and two other cylinders showed signs of "expansion" in that area.

 

[NickSezz]

Seems like its more likely related to harmonics. The pistons would have pitting and burned off edges if it was detonation. First thing I thought to myself, wonder what the tops look like.

IMHO this was not due to fuel, or detonation. It was due to harmonics, how fast was it spinning when it blew? What gear? Did you power shift it? Or if an auto did you firm up shifting? Again harmonics and maybe shock loading. Fuel cut off? Detonation usually chips the face first, right around the valve releifs and the edges of the top. Usually it takes chunks out the heads too.

I could also be way off base here, however in the past I have seen engines that were built blow to shreds because of harmonics, especially with the size of the piston in relation to length. For all intensive purposes the 5.0L engine has bad geometry for high revving, but the factory does it. For that matter so do ls7's. I do feel the harmonics of this engine are quite different from my previous 3v engine. The 3v was rougher at idle to around 2800rpm, then it smoothed like butter until 6800rpm where my rev limit was. The 5.0 is rugh from idle to 1500rpm then it smoothness out to about 5500, after that I can feel some bad harmonics, however the engine is so much more eager to rev that its hard to judge exactly the cut off.

That was an interesting post and made me start googleing some stuff.

http://en.wikipedia.org/wiki/Harmonic_balancer
to start simple with a wiki...makes ya think about some of these engines that went with no clear signs of detonation...

Cool read...
http://www.epi-eng.com/piston_engine_technology/torsional_excitation_from_piston_engines.htm
(multiple paged of info)

 

[luv2drum1]

Bummer in regards to your car. I am sure Lund Racing will get you squared away.

 

[KungFuHamster]

Seems like its more likely related to harmonics. The pistons would have pitting and burned off edges if it was detonation. First thing I thought to myself, wonder what the tops look like.

IMHO this was not due to fuel, or detonation. It was due to harmonics, how fast was it spinning when it blew? What gear? Did you power shift it? Or if an auto did you firm up shifting? Again harmonics and maybe shock loading. Fuel cut off? Detonation usually chips the face first, right around the valve releifs and the edges of the top. Usually it takes chunks out the heads too.

I could also be way off base here, however in the past I have seen engines that were built blow to shreds because of harmonics, especially with the size of the piston in relation to length. For all intensive purposes the 5.0L engine has bad geometry for high revving, but the factory does it. For that matter so do ls7's. I do feel the harmonics of this engine are quite different from my previous 3v engine. The 3v was rougher at idle to around 2800rpm, then it smoothed like butter until 6800rpm where my rev limit was. The 5.0 is rugh from idle to 1500rpm then it smoothness out to about 5500, after that I can feel some bad harmonics, however the engine is so much more eager to rev that its hard to judge exactly the cut off.

so do you suggest a good aftermarket harmonic balancer to take car of excess harmonics?

or add the boss damper? from what ive read it is different from the GT's and is made to hold up to the higher rpm of the boss.

 

[Twinscrewgt]

Ati super damper.

 

[jaguarking11]

Unfortunetly, I do not have the answer to this. But the balancer would not be a bad thing. However I still don't think the balancer would completely cure this. I believe that properly balancing and weight matching of pistons/rods/and crank counterbalancers would cure it. In short, the rotating assembly should be rebalanced. There is nothing like a speced engine. However its beyond most peoples means. Just remember you pay to play. Just gotta realize that the higher the hp levels the more fragile the engine can be. I remember a saleen blew the engine due to shock loading, the engine was a 3v, and had a forged rotating assembly, however he blew windows in the block anyway, at much lower power levels than guys who had factory 3v engines. He blew at 400whp. It was so bad the pistons that let go completely disintegrated and the remaining rods proceeded to saw the block in half.

I remember years ago, every high performance build used to balance flywheel/crank/balancer as one unit. Now they do not seem to do that anymore.

My previous post is speculation and based on what my engine feels like. I still think you can squeeze power out of these engines, I think 1000whp is possible on pump gasoline with a properly built 5.0L as a daily driver. However getting there takes cubic dollars.

 

[NickSezz]

Unfortunetly, I do not have the answer to this. But the balancer would not be a bad thing. However I still don't think the balancer would completely cure this. I believe that properly balancing and weight matching of pistons/rods/and crank counterbalancers would cure it. In short, the rotating assembly should be rebalanced. There is nothing like a speced engine. However its beyond most peoples means. Just remember you pay to play. Just gotta realize that the higher the hp levels the more fragile the engine can be. I remember a saleen blew the engine due to shock loading, the engine was a 3v, and had a forged rotating assembly, however he blew windows in the block anyway, at much lower power levels than guys who had factory 3v engines. He blew at 400whp. It was so bad the pistons that let go completely disintegrated and the remaining rods proceeded to saw the block in half.

I remember years ago, every high performance build used to balance flywheel/crank/balancer as one unit. Now they do not seem to do that anymore.

My previous post is speculation and based on what my engine feels like. I still think you can squeeze power out of these engines, I think 1000whp is possible on pump gasoline with a properly built 5.0L as a daily driver. However getting there takes cubic dollars.

I was driving behind my buddies 05 3V when it went down like that...Biggest cloud of smoke I ever saw come out of a car. lol

It blew up so bad pieces of the pistons made it up through the after-cooler, through the KB blower screws and into the intake pipe witch also had oil pouring out of it. Total loss...

 

[jaguarking11]

It had seen 7700 RPMS on datalogs. I was also datalogging and working on get the thing to shift into 3rd gear at WOT properly. What it was doing and a few I've talked to think may have been the cause of the failure. The car would pull hard through 2nd gear, all power would go away like the car shut off, it would shift, and then all power would come back. This is an automatic car. The night it went completely the new tune I just loaded had just shifted properly into 3rd gear at WOT for the first time and it did hit hard.

The other weird thing that was never worked out by the previous tuner was another with a shutdown of power. Merging into traffic no less the car will just lose all power like it was turned off and then take off again. If you started giving it throttle slowly it would flash RPMs and go to idle moreless. Then the throttle did nothing for 2-3 seconds. Left me hanging in oncoming traffic more than once to the point I parked it. Working with Lund Racing to get it dialed in and then dyno tuned soon.

That's why shift firmness needs to be softened the higher the gears go. For every gear up your increasing load dramatically on the engine, with higher load you get higher cylinder pressures and with higher pressures the metal deforms until it deforms enough to either crack or cause an imbalance. In rally cars with dog boxes they have ignition cut with every gear change, its such a small interval cut that its nearly seamless, they do it for two reasons, primary is for shifting, secondarily to reduce shock loading. Rally cars are hp and displacement limited, however they do not have torque limitations so they turbocharge engines to have as much torque as possible through the rev range and kill it off at higher rpm to keep within regulations of hp.

 

[Speed+Clinic]

I still think it had a detonation, look at the color. If this was a harmonics issue then why would only 1 cylinder show wear? The harmonics would go front to back and back to front.

 

[Speed+Clinic]

That's why shift firmness needs to be softened the higher the gears go. For every gear up your increasing load dramatically on the engine, with higher load you get higher cylinder pressures and with higher pressures the metal deforms until it deforms enough to either crack or cause an imbalance. In rally cars with dog boxes they have ignition cut with every gear change, its such a small interval cut that its nearly seamless, they do it for two reasons, primary is for shifting, secondarily to reduce shock loading. Rally cars are hp and displacement limited, however they do not have torque limitations so they turbocharge engines to have as much torque as possible through the rev range and kill it off at higher rpm to keep within regulations of hp.

The main reason for that in rally is: Boost, not loosing boost between gears + transmission doesn't torque bind so shifts are cleaner.

I doubt this is a harmonic balancer issue, it would had driven the knock sensor crazy...

 

[VET-KLR]

So far with new tuner..Ken with Lund Racing..no funky shifting crap and runs much better all around. Tuning process was done much safer and how it should be. Dynoing car on Tuesday next week and running at track on Friday. It's an 1/8 mile track and looking for low 7s at least. Can't wait!

 

[JerryC]

So far with new tuner..Ken with Lund Racing..no funky shifting crap and runs much better all around. Tuning process was done much safer and how it should be. Dynoing car on Tuesday next week and running at track on Friday. It's an 1/8 mile track and looking for low 7s at least. Can't wait!

With traction, you're going to hit that easy.

 

[VET-KLR]

I have 15x10 Darkstars with 27x10.5x15 ET Streets and hoping they work well. Going to get some MT 275x60x15s soon as these are worn out. I'm just not sure stock stall and gears will work out ok. Thinking about some 3.73s and wishing I would've got the stall while the motor was out. Also thinking about the lightest highest flowing exhaust from x-pipe back.

And so glad to have a Boss shortblock with forged pistons and Lund Racing tuning it.

 

[wbt]

So far with new tuner..Ken with Lund Racing..no funky shifting crap and runs much better all around. Tuning process was done much safer and how it should be. Dynoing car on Tuesday next week and running at track on Friday. It's an 1/8 mile track and looking for low 7s at least. Can't wait!

Hell....I am running low 7's N/A....you should be in the 6's me thinks.

 

[JerryC]

I have 15x10 Darkstars with 27x10.5x15 ET Streets and hoping they work well. Going to get some MT 275x60x15s soon as these are worn out. I'm just not sure stock stall and gears will work out ok. Thinking about some 3.73s and wishing I would've got the stall while the motor was out. Also thinking about the lightest highest flowing exhaust from x-pipe back.

And so glad to have a Boss shortblock with forged pistons and Lund Racing tuning it.

Should be no problem for you. I'm running 305 ET street radial II's on heavy 18x10's, stock gear and convertor. Stall it to about 1800-2000, mat it and then after your foot hits the floor let off the brake, that got me a 1.56 60'.

 

[jaguarking11]

I still think it had a detonation, look at the color. If this was a harmonics issue then why would only 1 cylinder show wear? The harmonics would go front to back and back to front.

That cylinder was running hotter than the rest? The injectors are not perfect? Manufacturing defect? Could be many things.

I think its shock loading still. Harmonics are not necessarily eliminated nor are they completely dampened by the harmonic dampener.


In any case, I could be way off base.

 

[Speed+Clinic]

That cylinder was running hotter than the rest? The injectors are not perfect? Manufacturing defect? Could be many things.

I think its shock loading still. Harmonics are not necessarily eliminated nor are they completely dampened by the harmonic dampener.


In any case, I could be way off base.

With tolerances how they are this days, that is more far fetch than years before. Although there is always the posibility of a faulty injector.

Shock loading wont affect just one cylinder, you should see it across the board. Atleast some scratches from the entire vibration since everything is riding on the same crankshaft. Im still betting it is a tune issue because of this.

So far with new tuner..Ken with Lund Racing..no funky shifting crap and runs much better all around. Tuning process was done much safer and how it should be. Dynoing car on Tuesday next week and running at track on Friday. It's an 1/8 mile track and looking for low 7s at least. Can't wait!