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Old 09-19-2010, 09:27 PM   #1
340Duster
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Default Lean Cylinder?

Sorry for the double post, but I think this is better suited here. I'm trying to figure out if this is what caused my piston to melt like butter. Here's the thread about it. I'm at a loss at the moment http://forums.nasioc.com/forums/show....php?t=2057556
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Old 09-22-2010, 05:54 PM   #2
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Quote:
Originally Posted by 340Duster View Post
I read mostly about cracked ringlands on the pistons, or spun bearings. It looks more like a lean condition on the cyl. Trying to figure out exactly what caused the erosion of the piston/ it melting to the bore. Sorry the second pic is from my phone.



bump for him, I just want to know what you guys think happened
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Old 09-22-2010, 06:23 PM   #3
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You got hella lean at the wrong time probably in boost. If you have an EGT gauge I'm sure you would have seen a big rise in temp before failure. Motoryder may have a thread somewhere about his melted piston adventure.
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Old 10-01-2010, 09:40 AM   #4
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Any more input? I had a very similar failure recently. My pics are in the linked thread in the OP.

I wasn't able to find much detail about Motoryder's melted piston.
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Old 10-01-2010, 09:53 AM   #5
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It could possibly be a cracked ringland that started the mess. The cracked ringland will cause scuffing, later enough scuffing for blowby, then oil, misfires, pre-det, then major piston failure and melting.

You'd have to take the piston out, make sure the rings don't turn so you know where the gap ends are, then inspect the piston to narrow in possible causes.
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Old 10-01-2010, 10:45 AM   #6
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Yeah, the rings won't move since they are destroyed right by were the hole melted through. Not sure I could even tell if there was a local crack in the area now...









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Old 10-01-2010, 11:45 AM   #7
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That's exactly how mine looks. I still haven't been able to get in touch with my tuner to get the files from my tune emailed to me. And haven't sent my injectors off as I have been toying with going with a 68HTA.

If there was a cracked ringland it would have to be small. As in now gone in the torched section of the piston. It is hard to tell as the rings are now fused to the piston. Could just det cause the erosion/ melting? I ask because I imagine it as a force acting on the piston in a way that would "break" the piston not melt it like ours.

yaya20, what kind of pistons were you running?
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Old 10-01-2010, 12:10 PM   #8
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Quote:
Originally Posted by 340Duster View Post
yaya20, what kind of pistons were you running?
Wiseco
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Old 10-01-2010, 12:12 PM   #9
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^^^ With that being said, I find the ringland thing highly unlikely. With my stock cast one sure, but not with a forged piston like that. They both did however, melt about the same way. This is great
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Old 10-01-2010, 12:13 PM   #10
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Originally Posted by yaya20 View Post
Any more input? I had a very similar failure recently. My pics are in the linked thread in the OP.

I wasn't able to find much detail about Motoryder's melted piston.
He's my neighbor and its possible he didn't post the failure here. You need to be very hot to melt a piston like that, way beyond normal combustion temps. About the only thing I can think of that would allow that would be an extremely lean condition. Those where his findings also.
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Old 10-01-2010, 12:20 PM   #11
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Originally Posted by kellygnsd View Post
He's my neighbor and its possible he didn't post the failure here. You need to be very hot to melt a piston like that, way beyond normal combustion temps. About the only thing I can think of that would allow that would be an extremely lean condition. Those where his findings also.
I'm basically trying to work with the shop that did my build and tune as my car had 750 miles on it since rebuilding the bottom end. The more detail I can get, the better discussion I can have with them about covering my motor. So far as I can tell, I did not have any part failures that caused the lean condition.
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Old 10-01-2010, 12:24 PM   #12
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Have you had the tune looked at closely or by another tuner for a second opinion?

Quote:
Originally Posted by yaya20 View Post
I'm basically trying to work with the shop that did my build and tune as my car had 750 miles on it since rebuilding the bottom end. The more detail I can get, the better discussion I can have with them about covering my motor. So far as I can tell, I did not have any part failures that caused the lean condition.
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Old 10-01-2010, 12:56 PM   #13
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Tricky situation, but no. Not yet.
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Old 10-01-2010, 02:31 PM   #14
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That damage is in no way caused by a broken ring or ring land. Its lean
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Old 10-01-2010, 10:34 PM   #15
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Faulty injector
fuel system problem
tune
check all three
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Old 10-01-2010, 10:53 PM   #16
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get the injectors checked out

what injectors?
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Old 10-02-2010, 10:49 AM   #17
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This looks definitely lean and might be caused by pre ignition due to being overly lean. There are no DET marks on the piston crowns. Pre ignition is the worst that can happen. Temperatures and cylinder pressures can go skyhigh in the blink of an eye. Many times it cannot be heard in the DET cans and no knock shows up. Even AFR may not show excessively lean as most people measure average AFRs of all 4 cylinders.

Most likely faulty injector or perhaps a clogged one. Also check wiring to make sure injectors are ok and clean mating connectors, etc.

Good luck on the rebuild.

Cheers,

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CS Racing
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Old 10-03-2010, 01:50 PM   #18
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I was running DW850s, they have been inspected and given a clean bill of health
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Old 10-03-2010, 05:35 PM   #19
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Quote:
Originally Posted by 340Duster View Post



Detonation in that cylinder, look at all the pitting on the piston dome. probably cracked a ring land and it was burning oil. When you burn oil with your gas you end up with very little octane, which would cause the cylinder to start to run super hot and melt.
Check your knock correction range, if it was around the stock setting of 6100 and you were revving to say 6800-7k that's about 1k rpms of no knock control, so it would not pull any ignition, or show a knock count. Not to mention it would be in the range were the td04 is pushing some seriously hot air which would tend to detonate a lot.

What was your timing and wideband AFR.. Hopefully you had a wideband or were tuned with one at least.

Quote:
Originally Posted by yaya20 View Post
Looks somewhat familiar... I'd start by getting your injectors checked out. Looks like cylinder 3???

Here is mine:
Lots of timing or very lean tune or both.. Look at your number 1 piston as well.. Corner nice and shinny. Your EGTs were probably pretty high when that melted. If it was a bad injector only 1 piston would look like it took some serious heat.
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Old 10-04-2010, 04:17 PM   #20
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bump for more answers?
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Old 10-04-2010, 05:19 PM   #21
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I think the answers are in the post above
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Old 10-04-2010, 05:25 PM   #22
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Like jkopinga said; pre-ignition. Melts holes in pistons really quick. Probably happened due to a lean condition and a lot of knock.

This is one of the better write-up on pre-ignition and detonation online:

http://www.streetrodstuff.com/Articl...ne/Detonation/
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Old 10-04-2010, 06:29 PM   #23
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While my piston wasn't on a boosted application it was melted from Detonation.
It was a 13.5 compression engine on 93 octane but I let a moron ride it and he just kept WFO till it melted
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Old 10-05-2010, 06:19 AM   #24
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Have had one Spec C engine blow the 2nd time now :-( It's probably also caused due to pre ignition. Checked everything. Fuel pump, injectors, etc. etc.

Had the DET cans on and nothing to be heard until there was suddenly a big cloud of smoke and oil splashing everywhere in the engine bay :-(

**** happens!

Cheers,

Jasper.
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Old 10-05-2010, 10:30 AM   #25
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Quote:
Originally Posted by Harman Motive, Inc. View Post
Like jkopinga said; pre-ignition. Melts holes in pistons really quick. Probably happened due to a lean condition and a lot of knock.

This is one of the better write-up on pre-ignition and detonation online:

http://www.streetrodstuff.com/Articl...ne/Detonation/
Good read, thanks for sharing that article.

Quote:
Originally Posted by jkopinga View Post
Have had one Spec C engine blow the 2nd time now :-( It's probably also caused due to pre ignition. Checked everything. Fuel pump, injectors, etc. etc.

Had the DET cans on and nothing to be heard until there was suddenly a big cloud of smoke and oil splashing everywhere in the engine bay :-(

**** happens!

Cheers,

Jasper.
Forgive my noobness, but if it were pre-ignition and not detonation, wouldn't the hole be in the center of the piston rather than at the bottom of the cylinder near the exhaust valves?
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