Measuring the piston ring groove condition
Moderator: Team
Re: Measuring the piston ring groove condition
Mahle MS and total seal run them like 0.02mm 0.0008" for 1mm rings no gas ports.
Shouldn't it be based on the axial thickness and or width in some way?
Shouldn't it be based on the axial thickness and or width in some way?
-
- Expert
- Posts: 546
- Joined: Sun Mar 18, 2012 11:37 pm
- Location:
Re: Measuring the piston ring groove condition
I've been watching this post and I feel that there is dangerous info being presented if its being used by the untrained or novice. I've seen FEA testing where that .0004 is all used up on the compression cycle when the piston is flexing. All it takes is a tad too much timing or a tick too lean to microweld that ring and groove into a useless mess. I'm retired but Friday I get the call, you know the call that means come to my shop, I have a problem? It was a "lost vacuum" call, this motor was using pistons with .0005 clearance and they hand lap the rings to get the clearance they really want. The reason they hand lap is because their $10000 ring sets aren't FLAT So I saw 4 rings that had voids on the sealing side, some near the gaps and others 180 degrees from the gaps-reduced sealing for sure. All this to say that sometimes we're not getting all the info on the WEB when these claims are made.
-
- Guru
- Posts: 4604
- Joined: Sun Sep 18, 2011 11:31 am
- Location: Heading for a bang up with Andromeda as we all are.
Re: Measuring the piston ring groove condition
If these or any used piston has ever been glassbeeaded without the ring grooves being taped off then there junk now if they where not before!!
You can cut a man's tongue from his mouth, but that does not mean he’s a liar, it just shows that you fear the truth he might speak about you!
Re: Measuring the piston ring groove condition
Someone needs to make a Piston ring groove Rebuilder in a spray can.
Re: Measuring the piston ring groove condition
What a safe way to soak aluminum piston ring grooves clean or at least easier to clean? I'm experimenting with a junk piston now, alternating between weak citric acid solvent and dishwasher soap water.
Paradigms often shift without the clutch -- https://www.youtube.com/watch?v=cxn-LxwsrnU
https://www.instagram.com/ptuomov/
Put Search Keywords Here
https://www.instagram.com/ptuomov/
Put Search Keywords Here
Re: Measuring the piston ring groove condition
Nope, I don't have an access to a machine like that.
Paradigms often shift without the clutch -- https://www.youtube.com/watch?v=cxn-LxwsrnU
https://www.instagram.com/ptuomov/
Put Search Keywords Here
https://www.instagram.com/ptuomov/
Put Search Keywords Here
Re: Measuring the piston ring groove condition
I have magnifying glasses and a microscope, so will do that. The microscope is old school so it can't take photos, though.engineguyBill wrote: ↑Sat Jun 22, 2019 8:39 pm First, inspect the ring groove with a lighted magnifying glass. Look closely at the bottom of the groove for pitting and other wear marks. If the ring groove looks like there is any wear whatsoever the pistons are junk. At this point you can measure the axial thickness of the groove to verify your observations.
Paradigms often shift without the clutch -- https://www.youtube.com/watch?v=cxn-LxwsrnU
https://www.instagram.com/ptuomov/
Put Search Keywords Here
https://www.instagram.com/ptuomov/
Put Search Keywords Here
Re: Measuring the piston ring groove condition
A novice question. If the ring is intended to rotate, as I think it's in all the car pistons I've seen, both the ring and the groove are flat by spec, right? "Flat" in this context meaning that if you cut the groove and ring radially from the piston center, the cross-section is the same. Is this true? I know that there can be taper, of course.DCal wrote: ↑Wed Jun 26, 2019 11:37 am I've been watching this post and I feel that there is dangerous info being presented if its being used by the untrained or novice. I've seen FEA testing where that .0004 is all used up on the compression cycle when the piston is flexing. All it takes is a tad too much timing or a tick too lean to microweld that ring and groove into a useless mess. I'm retired but Friday I get the call, you know the call that means come to my shop, I have a problem? It was a "lost vacuum" call, this motor was using pistons with .0005 clearance and they hand lap the rings to get the clearance they really want. The reason they hand lap is because their $10000 ring sets aren't FLAT So I saw 4 rings that had voids on the sealing side, some near the gaps and others 180 degrees from the gaps-reduced sealing for sure. All this to say that sometimes we're not getting all the info on the WEB when these claims are made.
If the above is true, then one of the piston design objectives must be that the ring groove stays as flat as possible, no matter how much combustion pressure, tension load, or temperature the piston sees. Easier said than done, of course.
Paradigms often shift without the clutch -- https://www.youtube.com/watch?v=cxn-LxwsrnU
https://www.instagram.com/ptuomov/
Put Search Keywords Here
https://www.instagram.com/ptuomov/
Put Search Keywords Here
Re: Measuring the piston ring groove condition
Yes and no.
i believe a few piston companies have looked into cutting the groove NOT perfectly straight, rather angled slightly up, in such a way that the groove WILL be straight once the piston is at running temps.
Compensating for the tendency of the top of the piston to be hotter than the bottom.
I'd say the "intention" to rotate is similar to how poppet valves rotate, or don't. USUALLY they do rotate, but sometimes they don't.....and even if they don't rotate, usually they work fine anyway.
IF there is really nothing to gain from pinning them in place.....then you may was well allow piston rings to rotate, and sometimes allowing them to rotate is beneficial to even out the wear.
Other times, less often but sometimes, it may work better if they do not rotate.
It can works both ways.
Have you ever heard this before?
"rings not sealing, I took it apart and all the gaps were lined up"
i have. In fact I've heard it so many times I know it means something....but what? I think... what it means is if the rings are NOT sealing, they tend to quit rotating and line up the gaps.
Note the cause and effect. Some people think is isn't sealing BECAUSE the gaps are lined up, but IMO that can't be true. Great mystery!
i believe a few piston companies have looked into cutting the groove NOT perfectly straight, rather angled slightly up, in such a way that the groove WILL be straight once the piston is at running temps.
Compensating for the tendency of the top of the piston to be hotter than the bottom.
I'd say the "intention" to rotate is similar to how poppet valves rotate, or don't. USUALLY they do rotate, but sometimes they don't.....and even if they don't rotate, usually they work fine anyway.
IF there is really nothing to gain from pinning them in place.....then you may was well allow piston rings to rotate, and sometimes allowing them to rotate is beneficial to even out the wear.
Other times, less often but sometimes, it may work better if they do not rotate.
It can works both ways.
Have you ever heard this before?
"rings not sealing, I took it apart and all the gaps were lined up"
i have. In fact I've heard it so many times I know it means something....but what? I think... what it means is if the rings are NOT sealing, they tend to quit rotating and line up the gaps.
Note the cause and effect. Some people think is isn't sealing BECAUSE the gaps are lined up, but IMO that can't be true. Great mystery!
-
- Guru
- Posts: 3285
- Joined: Wed Jun 25, 2008 1:46 pm
- Location: NC
Re: Measuring the piston ring groove condition
engineguyBill wrote: ↑Sun Jun 23, 2019 5:11 pm .0010" ring to groove clearance is the minimum I would recommend in any high performance/racing engine, regardless of ring material or whether or not gas ports are utilized. Any less clearance will very likely result in ring problems.
-
- Guru
- Posts: 1649
- Joined: Tue Mar 06, 2007 7:23 pm
- Location: San Tan Valley, AZ
- Contact:
-
- Guru
- Posts: 1264
- Joined: Fri Feb 26, 2010 11:15 am
- Location: Gold Canyon, AZ
Re: Measuring the piston ring groove condition
Yup!!!Warp Speed wrote: ↑Thu Jun 27, 2019 7:43 amengineguyBill wrote: ↑Sun Jun 23, 2019 5:11 pm .0010" ring to groove clearance is the minimum I would recommend in any high performance/racing engine, regardless of ring material or whether or not gas ports are utilized. Any less clearance will very likely result in ring problems.
Bill
Perfect Circle Doctor of Motors certification
SAE Member (30 years)
ASE Master Certified Engine Machinist (+ two otherASE Master Certifications)
AERA Certified Professional Engine Machinist
Perfect Circle Doctor of Motors certification
SAE Member (30 years)
ASE Master Certified Engine Machinist (+ two otherASE Master Certifications)
AERA Certified Professional Engine Machinist
Re: Measuring the piston ring groove condition
I'm confused on the end of this post. Jay, are you agreeing with Bill on the vertical clearance of .001 minimum?