Well fuck. At this point, everything points to a cracked or broken ringland. The clutch pedal doesn't fight my foot, although there is a small vibration when pressing on it slightly in gear. I guess it's time to start saving for an engine build... :grumpy: Thanks for the link @Dano;

Edit: @Dano; do you have pictures of your spark plugs?

I found this quote from NASIOC in a thread that @Dano; posted:
In my eyes, albeit in a different engine, this is part of our problem. As combustion starts, I believe our pistons are doing exactly what he is talking about. The ringlands are cracking on the exhaust side, which matches up perfectly with his description of what is happening as you increase spark advance. The exhaust side of the piston is being forced against the cylinder wall and the excess pressure and friction causes it to crack.

Is this a viable explanation or am I talking out of my ass?

Side loading goes up as the piston moves down the cylinder. Right at the top there is nearly zero side loading.

Zigatapatalka

I understand that, but after the spark plug fires, the piston is moving down... Can you elaborate? Maybe me saying "as combustion starts..." is causing some confusion. I'm not saying this is the ONLY problem, but rather a piece of the puzzle. Many other things that come with over-advanced timing, can also cause problems with ringlands. Like the excessive in cylinder temps and higher pressures for longer periods of time. The OEM pistons were not made with any of these things in mind.

Nice find.

He also talked a little about colder plugs. Maybe there is something there as well. A lot of people here are running colder plugs, but is it REALLY necessary? He claims he is only running step colder plugs on a 600AWHP track car.

Pressure against the cylinder wall is unlikely to cause the piston to crack since the force is applied over a relatively large area. The most common way ringlands crack is through detonation. Improper gap will also do it if the ring ends butt against each other but you have to consider expansion rates and if this is the likely culprit.

We know detonation is common on heatsoaked vehicles and it takes out rods. It could be that it takes out ringlands as well over time.

I completely agree in terms of detonation. That is a well known cause for ringland issues, but that stills begs the question, are we over-advancing timing at any point in the RPM range? I think we should be looking more closely at the RPM range where we are making peak torque, rather than at redline and peak timing values.

I know some EvoX enthusiasts here in Russia had the same ringland failure issue.. Now they increase the top ring gap slightly and the engine performs very well after that.
Isn't it an option for our engines?

http://img.tapatalk.com/d/13/03/30/daqemuhu.jpg
Anyone had this problem before? Lol
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That's what Dano plans to do on his virgin motor.

Is that out of your car? If so what cylinder

Sent from your couch

do you know how much they are opening up the gap by?

my current plan is to open up the top OEM gap which is .0056-.0094 and take it to .011 or maybe .012.

Leave the 2nd ring gap as is at .013-.017 IF its at the larger end of spec if not I'll open it up as well. got to keep the 2nd ring gap larger than the 1st to prevent ring flutter.

I just want a lil insurance but I think heat management and proper tune is the majority of the issue.

I have. It happened on my motor on cylinders 1,2 and 3.

Open that top ring to .015"

Cylinder 3 held. Only 45psi and I was like fuck it I can't drive it anymore ripped the block apart and found that two days ago lol

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yes I had considered going that big [ getting closer to aftermarket gaps] but that would precipitate the need to open up the 2nd gap as well. I really want to touch as little as possible. IDK

I guess it will depend on how the gaps look when I take it apart and I'll plan to open them up accordingly.

I'll post it up in my new thread when the time comes and get opinions.

I'll find this out and will write back here.

Still waiting for the information from the guys.. They behave like primadonnas, so it will take some time.

Meanwhile, this might be interesting to read: Analyzing a critical engine flaw in the 4b11 by TTP - evolutionm.net

looks like their top ring gap is .007 as well as ours and its too tight for the heat generated by more HP. Great information to know. I am thinking of going to .012 for my top ring gap and if the 2nd is already at max spec of .017 it will stay as is. These gaps are subject to change depending on what the gaps in the new motor measure out to as is.

thanks

Can you give me the following info?

Model/Year:
Mileage:
Compression Results:
Cylinders /w Cracked Ringlands:
Suspected Event Causing Failure and Other Info:

I'll add it to OP for documenting purposes.

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So did the failure happen before you bought the vehicle? Was it stock when you got it?

hmm, all of the cylinders have low compression, what can be the cause?

The gauge.

couldn't tell really until 2 weeks after we got it running that the fuel mileage sucked and random knock when partial throttle, so i finally decided to do a compression test and those were the numbers.:( car had intake and full 3'' exhuast and trans was fucked when we got it

No smoke pouring out the back?

Sent via stocked out for a while ...

When I let the car idle for a bit it starts smoking thought it was the turbo but it seems fine when I took it out

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Any reason not to run gap less rings?

Edited. . Reading fail

sent from my phone usings my fingers

Haha - it happens. I'm just curious as I have experience with them in a NA engine, but not sure of their feasibility in a boosted application. They seem to have a little more tolerance for heat due to the overlapping portions.

So here is some forensic evidence from my old motor showing what I think was rings butting along with some from another piston that did not appear to butt.

All I have is an iPhone 4 and thus the focal length is just too long to get a great close up pick but here is what I have.

Exhibit A: From broken piston - cyl 3

Top ring side A

http://mail.netsecurenow.com/img/ringland/1a.jpg

Top ring side B

http://mail.netsecurenow.com/img/ringland/1b.jpg

2nd ring side A

http://mail.netsecurenow.com/img/ringland/2a.jpg

2nd ring side B

lost this pic somehow

Exhibit B: From undamaged piston - cyl 1

Top ring side A

http://mail.netsecurenow.com/img/ringland/3a.jpg

Top ring side B

http://mail.netsecurenow.com/img/ringland/3b.jpg

2nd ring side A

http://mail.netsecurenow.com/img/ringland/4a.jpg

2nd ring side B

http://mail.netsecurenow.com/img/ringland/4b.jpg

Exhibit C: Broken piston - cyl 3

this is the exhaust side, rings in original orientation as they were when removed from the motor.

http://mail.netsecurenow.com/img/bui...wn/piston1.jpg

ringland remnant: To me it looks like the carbon has been rubbed off at a 90* angle to the ringland where the ring gap rested.

http://mail.netsecurenow.com/img/bui...wn/piston4.jpg

cylinder 3 piston top

http://mail.netsecurenow.com/img/bui...wn/piston3.jpg

cylinder liner

http://mail.netsecurenow.com/img/bui.../cylinder3.jpg

I thought this was interesting in how my virgin piston rings were lined up. Exhaust side. All were the same with very little overlap between the 1st and 2nd rings.

oil ring gap was on the other side 180 apart from these

http://mail.netsecurenow.com/img/ringland/newpiston.jpg

IIRC the manual calls for 90 deg separation between ring gaps.
I stabbed them in a star shape separation (120 degrees) with the top compression ring gaps pointing toward the injectors.

yeah well the japs that built this motor didn't do that and they left one of the baffles out of the pan. Like Easter Bunny said...this thing was assembled on a Friday afternoon.

You guys may know this already, but piston rings rotate as the piston moves up and down, so the orientation is not how it was from the factory.

@Dano; it's hard to tell from the picture, but is your cylinder wall scored from the broken ringland? Was the block still re-useable?

this motor was never run and they were that close was my point.

yes and yes....honed them out with a 500 grit hone.

Oh, I thought these were the rings from your engine with the cracked ringland. Lol. My bad.

How much material did you end up removing from the cylinder wall to make it useable?

Dan, the piston that blew could have been letting fuel come into contact with the ring ends after the break thus washing them clean. How do the ring ends look on the other cylinders 2 and 4?

carbon coated like the ones pictured.

its hard to tell from the pic but that ring looks freshly ground on one side...its that clean and I didn't touch it. The other side is clean on 1/3 of it at an angle as you can see. not sure how to explain that.

I know it's asking for more work, but can you measure the failed ring end gap? I'd say it's probably safe to even do it in the new motor.