Editing Forums/Z31P/z31-repairs-forums engine-mechanical/Broken Ring land at 20psi

{{ForumImport
|op_user=Wilsonthesphere
|op_date=2018-04-10 13:53:05
|post_count=9
|archive_url=/Z31performance_archive/forum/z31-repairs-forums/engine-mechanical/539295-broken-ring-land-at-20psi.html
}}

'''Wilsonthesphere:''' <small>(2018-04-10 13:53:05)</small>

Just wanted to post real life experience of broken ring land so it can help others with their tuning. A lot other forums can be too much of a echo chamber of hearsay .

Afr's were around high 9s to low 10s with 450cc injectors. I was about 90% injector duty cycle at 40psi of fuel pressure. Stock timing map. Engine felt really strong and consistent. Then after a hard pull It felt down of power with a different exhaust tone. Pulled into a gas station and there was a lot of blow-by. The OEM head gasket appears to be fine with no signs of failure. Not sure how much power I was making but I only have enough fuel for between 350-375 hp. Seems low for what others have reported breaking ring lands at.

Off to build a forged bottom end now.

Only piston #2 failed the clean piston pic is how the other ones look like. No signs of detonation anywhere.

[archived image: 20180409-201929.jpg]

[archived image: 20180409-201937.jpg]

[archived image: 20180409-201957.jpg]

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'''mwolvinm:''' <small>(2018-04-10 17:14:59)</small>

better check that head really good for cracks before you reuse it… Are those aftermarket cast pistons?

The middle picture looks like the piston is not centered in the bore too.

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'''Wilsonthesphere:''' <small>(2018-04-10 18:02:02)</small>

{{Quote|user=mwolvinm|better check that head really good for cracks before you reuse it… Are those aftermarket cast pistons?

The middle picture looks like the piston is not centered in the bore too.}}

Stock pistons, I didn't notice that piston does look off center not sure if that's normal or not. I did refresh the engine with bearing and new rings. Took it to a machine shop for them to hone it so the bore should be the same.

Did do a brief look at the head when I first took it apart and it looked fine. Ill probably build a VG33 and try to use those heads.

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'''FlawleZ:''' <small>(2018-04-11 10:57:10)</small>

What was your compression before you reringed it and put it new bearings?

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'''Wilsonthesphere:''' <small>(2018-04-11 13:53:22)</small>

{{Quote|user=FlawleZ|What was your compression before you reringed it and put it new bearings?}}

I didn't compression test it after the rebuild. You think uneven compression results would cause failure on the piston with the highest compression result?

I also did drive with the driver side cylinder off a tooth for about 50-80 miles. No sure if that would cause slight detention and already weaken the piston.

FlawleZ what boost are you running?

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'''FlawleZ:''' <small>(2018-04-11 16:23:43)</small>

{{Quote|user=Wilsonthesphere|I didn't compression test it after the rebuild. You think uneven compression results would cause failure on the piston with the highest compression result?

I also did drive with the driver side cylinder off a tooth for about 50-80 miles. No sure if that would cause slight detention and already weaken the piston.

FlawleZ what boost are you running?}}

No I mean what was your compression results before you reringed or rebuilt it? Why was it reringed in the first place? I don't think uneven compression itself would cause this, I think there was an underlying issue that's to blame.

I'm running 18 psi usually but when I want I run 22-24. 545 RWHP was measured at 22 psi.

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'''Wilsonthesphere:''' <small>(2018-04-11 17:59:25)</small>

{{Quote|user=FlawleZ|No I mean what was your compression results before you reringed or rebuilt it? Why was it reringed in the first place? I don't think uneven compression itself would cause this, I think there was an underlying issue that's to blame.

I'm running 18 psi usually but when I want I run 22-24. 545 RWHP was measured at 22 psi.}}

I was burning quart of oil day with my previous build after flogging a lot it with the Holset I assumed it was the engine burning old so I just tore it apart with out testing. As with assumptions I felt like a ass when the engine was fine and the oil burning came from a blown oil seal on the Holset. I rebuilt it anyway while I was in there.

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'''FlawleZ:''' <small>(2018-04-12 03:08:38)</small>

{{Quote|user=Wilsonthesphere|I was burning quart of oil day with my previous build after flogging a lot it with the Holset I assumed it was the engine burning old so I just tore it apart with out testing. As with assumptions I felt like a ass when the engine was fine and the oil burning came from a blown oil seal on the Holset. I rebuilt it anyway while I was in there.}}

I see. I was just about to say I hear and see of people doing this a lot on their VGs and unless there's specific evidence often times its unnecessary and a lot of people just introduce more potential of problems or human error in reassembly.

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'''Wilsonthesphere:''' <small>(2018-04-13 17:31:37)</small>

Very possible. I have a spare unmolested used turbo block that I will install for now and save the money for now. If I crack the 400 hp mark will be very happy.