Engine Blew!

[brandonblt2]

Damn sorry to see this. I definitely used your build as inspiration for mine in a few areas. Well I know now to keep my current conservative tune for my edelbrock. I'll be looking forward to see what you do next since my motor probably isn't too far behind yours since I'm pushing 166k on the motor.

[Capt Spaulding]

The audio is interesting. Trying to sort out the RUD (Rapid Unscheduled Disassembly) process is even more so. I really wonder what broke first. The most obvious candidate is the rod, but I kinda wonder about the piston.

In the end, I've concluded that when you boost one of these things, it becomes something like a Schrodinger's engine. Both alive and dead - depending on an event which may not happen.

[Irace86.2.0]

Originally Posted by Capt Spaulding

The audio is interesting. Trying to sort out the RUD (Rapid Unscheduled Disassembly) process is even more so. I really wonder what broke first. The most obvious candidate is the rod, but I kinda wonder about the piston.

In the end, I've concluded that when you boost one of these things, it becomes something like a Schrodinger's engine. Both alive and dead - depending on an event which may not happen.

The audio is best heard with quality headphones. They whistling shreak before destruction makes me think the oil barrier failed. Was it oil starvation, cold oil, cumulative/chronic excessive stress, detonation or preignition excessive stress…? I don’t know. Maybe it was a combination of things, but what I can’t wrap my head around is how that piston was destroyed.

I feel like if it was too much cylinder pressure from detonation or preignition then the excessive heat and pressure would have been revealed itself in damage to the top of the piston, but there was none outside of a clear, single, strike marks from the valves, and the damage was mostly from the bottom. It is odd.

The pictures of this bent rod and the destroyed bottom of the piston (see below) give credence to the theory that my connecting rod could have bent enough to cause piston damage, and then ripped apart as it nunchucked in the block after destroying the piston. How else could that have happened? It actually makes sense too because if there were high forces that would cause compression to the rod, but if it bottomed out against the bearing then there would have been an instant of rotational/sheer force leading to bending maybe. I’ve seen bent rods from FA20s, so it is possible. Plus, the head of my rod bolt snapped off like this guy, so lots of similarities.

https://www.eng-tips.com/viewthread.cfm?qid=385394

[Capt Spaulding]

Originally Posted by Irace86.2.0

The audio is best heard with quality headphones. They whistling shreak before destruction makes me think the oil barrier failed. Was it oil starvation, cold oil, cumulative/chronic excessive stress, detonation or preignition excessive stress…? I don’t know. Maybe it was a combination of things, but what I can’t wrap my head around is how that piston was destroyed.

The condition of the piston is what I have found puzzling. It appears to have been damaged from below - almost as if it broke at the wristpin journal.

Originally Posted by Irace86.2.0

I feel like if it was too much cylinder pressure from detonation or preignition then the excessive heat and pressure would have been revealed itself in damage to the top of the piston, but there was none outside of a clear, single, strike marks from the valves, and the damage was mostly from the bottom. It is odd.

My thoughts exactly.

Originally Posted by Irace86.2.0

pictures of this bent rod and the destroyed bottom of the piston (see below) give credence to the theory that my connecting rod could have bent enough to cause piston damage, and then ripped apart as it nunchucked in the block after destroying the piston. How else could that have happened? It actually makes sense too because if there were high forces that would cause compression to the rod, but if it bottomed out against the bearing then there would have been an instant of rotational/sheer force leading to bending maybe. I’ve seen bent rods from FA20s, so it is possible. Plus, the head of my rod bolt snapped off like this guy, so lots of similarities.

https://www.eng-tips.comThe/viewthread.cfm?qid=385394

This is makes sense to me. The link was quite interesting. The idea that the piston broke under tension was one of my first reactions. Still, I have no clue why.

[Irace86.2.0]

The link makes it clear that the piston could bend in any direction under load. Maybe my piston bent from fatigue under load, and then it caused the whistling grind before catastrophic failure.

I feel like bearing failure on a single cylinder from oil starvation is unlikely under the conditions I was in, but possible, and it is unlikely to cause total catastrophic failure, IMO, and not just rod knock or something.

It seems more likely that the rod bent from high pressure and chronic fatigue, and then it caused pressure to build on the rod bearing, and then the harmonics and internal forces ripped the rod from the bottom of the piston, and then the rod tore through the block, breaking apart in the process. That is my best guess.

[Capt Spaulding]

Originally Posted by Irace86.2.0

The link makes it clear that the piston could bend in any direction under load. Maybe my piston bent from fatigue under load, and then it caused the whistling grind before catastrophic failure.

I feel like bearing failure on a single cylinder from oil starvation is unlikely under the conditions I was in, but possible, and it is unlikely to cause total catastrophic failure, IMO, and not just rod knock or something.

It seems more likely that the rod bent from high pressure and chronic fatigue, and then it caused pressure to build on the rod bearing, and then the harmonics and internal forces ripped the rod from the bottom of the piston, and then the rod tore through the block, breaking apart in the process. That is my best guess.

Works for me. It was an impressive failure. I wonder what the fatigue life on these pistons is? Also, might the increased thermal (and possibly shock) load boost puts on them shorten that life?

[Irace86.2.0]

Originally Posted by Capt Spaulding

Works for me. It was an impressive failure. I wonder what the fatigue life on these pistons is? Also, might the increased thermal (and possibly shock) load boost puts on them shorten that life?

They are cast aluminum pistons, right? I don't know, but this gives credence to the idea that pistons need to be upgraded along with rods. Under normal wear and tear, I think the weakest link is the piston skirt. They have a tendency to accumulate the most wear, and they probably see the most lateral forces, but I think anything can develop fatigue. It probably depends on the engine and the type of wear/abuse it is seeing, which may be similar across drivers or unique to certain drivers.

https://www.irjet.net/archives/V3/i4/IRJET-V3I4330.pdf

Check out some of these pictures. Because the other pistons/rods were fine, I am thinking this was less of a power issue like the guy in the link and more of a single cylinder event brought on by oil starvation to that bearing and potentially cumulative wear to the bearing or something just mildly out of tolerance.

https://www.ft86club.com/forums/showthread.php?t=49767

[Capt Spaulding]

I suspect a rod bent like that would cock the piston in the cylinder generating all sorts of stresses on the piston and the rod. From there - several things could break. Your experience (along with others) has convinced me to forego boosting this engine. If I were to consider it, I think good rods (e.g. Carrillio) and good forged pistons would be on my list of requirements.

[x808drifter]

Can we get head on shots off the rod pieces.
I'd like to see the marks where they rod came apart.

[Irace86.2.0]

Originally Posted by Capt Spaulding

I suspect a rod bent like that would cock the piston in the cylinder generating all sorts of stresses on the piston and the rod. From there - several things could break. Your experience (along with others) has convinced me to forego boosting this engine. If I were to consider it, I think good rods (e.g. Carrillio) and good forged pistons would be on my list of requirements.

I think a bar of boost with E85 and a header is too much. A basic CARB kit on pump gas or E85 that is just a daily driver and not a track car will probably last the life of the car.

[Irace86.2.0]

Originally Posted by x808drifter

Can we get head on shots off the rod pieces.
I'd like to see the marks where they rod came apart.

I'll work on that later, but the two ends probably aren't the two ends that fractured. I am missing some of the middle of the rod, so it either broke in multiple pieces, or after it broke, it was again torn apart, as it sliced through the block.

[Irace86.2.0]

Thinking of pulling the trigger on a G25-660 0.72ar. It has the response and enough top end for a K24 build and for any future builds. Crazy how much power these new small turbos are making.

https://chromjuwelen.com/items/item/...70-whp-on-dyno

[Tcoat]

Originally Posted by Irace86.2.0

It definitely could have been slowly getting worse and worse, but then it finally gave out. Perhaps it didn't have a chance to knock because it caused immediate failure. I really can't remember, but I believe the bearing was in place, and I know the rod that snapped could freely spin around the journal, but another part of me thinks the bearing could have rotated about 5-10mm out of position. I remember one bearing being like that, but I couldn't recall if it was from the broken rod or another and just a product of the disassembly. What is obvious is that the tort head of one of the rod bolts snapped off. When, I don't know. The journal wasn't visually that damaged, unlike the bearing, but maybe because it is forged, it survived better, and maybe the bearing heated up or something, but it wasn't like I was driving for miles or weeks with rod knock like people can do.

The oil was recently changed and good, but it may have been too cold, and I could have sloshed the oil going through the 'S' curve of the left, right, right turn, but I typically need to wait for the car to clear the bucked asphalt at the apex of the corner, or the car just will lose traction. Typically, I would hit the bump then wait a second for the car to straighten out before getting on it, and that seems to be mostly the case, so while it is possible the oil starved because of lateral movement, mixed with cold temps, I just don't know.

Here is the thing: I have been listening to the video over and over. Unfortunately, the video is just from a dash camera from inside the car, and there is music and loud road noise. I used Audacity to try to isolate the sound, and when I did the best I could, I can swear I hear a squeal/whistle before the engine explodes. The squeal/whistle could be the tires breaking loose a little, but this is unlikely, as that would have decreased the stresses on the motor, so it is more likely that the squeal/whistle could be bearing surface contact. Maybe there was too much force and not enough oil to protect the surface, and once the surface made contact under high load, it set off a chain of events that caused the failure.

Listen to the audio. There is a squeal right before the destruction. Still, I don't get how the rod tore through the bottom of the piston and then disintegrated in half, or did it disintegrate and then stick the piston? Who knows?

I am of the opposite opinion. Rod snapped. Took out bearing. Launched piston into valves. Then slapped around in there for a bit creating the rest of the mess. I did it more than once a few decades ago. Classic results.

[Irace86.2.0]

Originally Posted by x808drifter

Can we get head on shots off the rod pieces.
I'd like to see the marks where they rod came apart.

Here you go sir. On a closer inspection, the rod is bent to the side. It is subtle, but it is there. This bending is 90 degrees to the direction it was spinning. This suggests the bending wasn’t a consequence of spinning around and tearing through the block. Like nunchucking through the block happened, and it probably finished the rod off, but I bet the bend caused the internal stress on the piston and ripped the bottom of the piston to pieces and then it all went downhill from there.