In normal operations , do piston rings rotate around the piston , as the engine runs ? Or , do they stay in place ?
Thanks ,
Thanks ,
Piston rings
- Thread starter WyrTwister
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Yes they do to some degree, this should answer your questions.
https://www.highpowermedia.com/blog/3954/rotation-of-piston-rings
https://www.highpowermedia.com/blog/3954/rotation-of-piston-rings
I was wondering about oil consumption & blow by , if the ring gaps moved to where they " lined up " .
I have also heard of rings becoming " stuck " from deposits of " crud " .
Thanks ,
I have also heard of rings becoming " stuck " from deposits of " crud " .
Thanks ,
Originally Posted by Trav
Yes they do to some degree, this should answer your questions.
https://www.highpowermedia.com/blog/3954/rotation-of-piston-rings
Pretty wild. I'm guessing it varies, bore to bore. Subtle finish differences might give slightly different forces and maybe cause a rotation. What I found interesting was the notion that don't rotate in sync--might explain why an engine drinks for a bit then stops. Maybe the stars lined up then unaligned.
Yes they do to some degree, this should answer your questions.
https://www.highpowermedia.com/blog/3954/rotation-of-piston-rings
Pretty wild. I'm guessing it varies, bore to bore. Subtle finish differences might give slightly different forces and maybe cause a rotation. What I found interesting was the notion that don't rotate in sync--might explain why an engine drinks for a bit then stops. Maybe the stars lined up then unaligned.
When fitting a piston, I was told to space the ring gaps equidistant from each other. Then I heard that the rings rotate. If so, then they must rotate at the same rate. If they didn't, then the gaps could align and decrease compression. I have NEVER heard of that happening So now there are 2 guys asking. TIA
Kestas
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I too took great pains to line up the ring gaps in the most ideal pattern for my V8. Now I'm hearing it's random in less than a minute operation!
Oil rings do not rotate relative to each other because the spacer friction locks them
However the second and top ring align there is a tiny increase in consumption and in blowby.
Motorcycles with boxer style engines will quite famously emit an occasional and impressive cloud of smoke after being parked on side stand, one solution's for this was to pin the rings so they do not rotate.
2 cycle engines with big ports also pin rings so the ends do not line up with the ports and snag an edge.
For the most part, a small amount of oil makes an impressive amount of smoke. There is an increase in consumption. It is usually negligible.
Rod
However the second and top ring align there is a tiny increase in consumption and in blowby.
Motorcycles with boxer style engines will quite famously emit an occasional and impressive cloud of smoke after being parked on side stand, one solution's for this was to pin the rings so they do not rotate.
2 cycle engines with big ports also pin rings so the ends do not line up with the ports and snag an edge.
For the most part, a small amount of oil makes an impressive amount of smoke. There is an increase in consumption. It is usually negligible.
Rod
I have also read to stagger the ring gaps on the rings on the bolt head of an AR .
Interesting... I've always set them up the gaps to be 180 degrees from each other when installing the pistons into the cylinders and knew that they move a bit but had no idea they moved this much this quickly as the article Trav posted, describes.
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How come they don't pin the ring to a fixed location like in 2 stroke?
I set ring gaps to be spaced 120 degrees apart but, no ring gap lined up with the piston pin.In the past, I've removed many pistons and have observed that almost all rings have maintained an approximate 120 degree separation in the gap placement. This observation, leads me to believe that piston rings in 4 cycl auto engines rotate very little. The last time I set up a piston with new rings was about 30 years ago, so things might have changed though. Ed
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Interesting reading, thanks.
I've assembled and disassembled many engines. I can't think of a time (other than in a two stroke with pinned piston rings) where rings remained in the position I'd assembled them.
I have seen scored cylinders where a ring had a groove worn so badly that it remained in place and was prevented from rotating.
I've assembled and disassembled many engines. I can't think of a time (other than in a two stroke with pinned piston rings) where rings remained in the position I'd assembled them.
I have seen scored cylinders where a ring had a groove worn so badly that it remained in place and was prevented from rotating.
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with the VW four cylinder inline engine, some tend to have the compression ring gaps line up with one another.
that is after hundreds of thousands of miles being buzzed up to 70 mph + with an eighties three-speed automatic transmission.
I just blamed harmonics. Have no idea if a five speed transmission would do the same. someone here may know?
that is after hundreds of thousands of miles being buzzed up to 70 mph + with an eighties three-speed automatic transmission.
I just blamed harmonics. Have no idea if a five speed transmission would do the same. someone here may know?
Just guessing here. Fixing the rings would cause them to stick easier because rotation would keep the grooves clean. That allows compression to get between the ring and the groove to expand it toward the cylinder bore. Thank you Trav for link
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Originally Posted by andyd
That allows compression to get between the ring and the groove to expand it toward the cylinder bore. Thank you Trav for link
I thought that rings expanded toward the bore during engine deceleration i.e. downshifting to slow the vehicle instead of the foot brake.
That allows compression to get between the ring and the groove to expand it toward the cylinder bore. Thank you Trav for link
I thought that rings expanded toward the bore during engine deceleration i.e. downshifting to slow the vehicle instead of the foot brake.
Originally Posted by LoneRanger
Originally Posted by andyd
That allows compression to get between the ring and the groove to expand it toward the cylinder bore. Thank you Trav for link
I thought that rings expanded toward the bore during engine deceleration i.e. downshifting to slow the vehicle instead of the foot brake.
The rings are always pushing against the bore (except when worn out and have lost their springiness!). But on turbocharged engines sometimes they will put a small hole in the ring land above the ring to port some of the pressure behind the ring, so as to apply more force to get it to seal harder.
Otherwise I don't think pressure (positive or negative) matters that much.
Originally Posted by andyd
That allows compression to get between the ring and the groove to expand it toward the cylinder bore. Thank you Trav for link
I thought that rings expanded toward the bore during engine deceleration i.e. downshifting to slow the vehicle instead of the foot brake.
The rings are always pushing against the bore (except when worn out and have lost their springiness!). But on turbocharged engines sometimes they will put a small hole in the ring land above the ring to port some of the pressure behind the ring, so as to apply more force to get it to seal harder.
Otherwise I don't think pressure (positive or negative) matters that much.
It does help break them in but what most people don't realize that most of that happens in the first 20 min of operation, in other words the lot boy more or less finished breaking them in.
They do continue to "fit" better over the miles but its not the same.
They do continue to "fit" better over the miles but its not the same.
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