Quote:
Originally Posted by BillGrissom
I agree w/ Kestreltom. After reading the link in post 49, the photo in post 53 shows horizontal boring marks which shouldn't be visible after a proper honing.
I have read different things about rings spinning in the piston grooves. One story is that when GM first switched to robot assembly, they installed rings with all the grooves aligned. That caused excessive oil consumption. Might be an apocryphal story since if the rings do spin they would soon randomize the gaps. I can't envision them spinning since seems like the sharp ends would dig into the aluminum to lock them in place, and if it spun seems it would machine away the aluminum grooves like a turning tool would.
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The spinning is more of a low speed walking, if the never walked around there would be a unworn area on the piston land where the ring gap resided.
I'd doubt the GM story as why would the robot be set up to make an effort to align the ring gaps?
I remember reading a story how Chrysler measured ring rotation in the 60's using radioactive material embedded in the piston ring. I can't find that article but did find this one.
http://kns.org/jknsfile/v31/A04803285773.pdf
The rotational speeds vary from 0.5 to 3 RPM
An interesting side note is they are using a hydrogen fueled engine that allows real time measurement of oil consumption by monitoring exhaust gas for CO2 and CO.
With this they round that lined up ring gaps increase oil consumption. However I'd say that since rings rotate, increased oil consumption would be limited to the times the rings are lined up.
I'd think that an engine with a 3 piece oil ring would be less susceptible to the top and 2nd ring gaps being lined up since the oil ring does not have a gap.
Also read through this
piston ring position - Engine & fuel engineering - Eng-Tips