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Re: single compression ring piston
Posted: Fri Jan 31, 2020 11:30 pm
by Schurkey
1986
GM is selling engines to the general public with full warranty and two-ring pistons.
I don't remember which engine it was. Geo Metro? Toyolet? Sprint? It was one of the captive-import jobs, and it may have been sold as a Chevrolet in the pre-GEO days.
Re: single compression ring piston
Posted: Sun Feb 02, 2020 11:48 am
by rebelyell
bentvalves wrote: ↑Fri Jan 31, 2020 12:04 am
so I am considering blocking the thrust side oil squirt hole in the big end of the connecting rod to give this 2 groove piston a fighting chance at actually controlling oil on the bore.
think I'm askin' for trouble going this route fellers?
Yes, also some loss of piston cooling.
? Have you checked with NPR ? Nippon Piston Ring? NPR is a major manufacturer of PISTONS as well as rings and they have plant(s) in USA
heck they even make pistons for GM's sbc.
http://www.npramerica.com/nprofamerica_product.html
Re: single compression ring piston
Posted: Sun Feb 02, 2020 2:21 pm
by ProPower engines
bentvalves wrote: ↑Thu Jan 16, 2020 7:12 pm
dear speedtalkers,
I am building a datsun a15 engine for a fellows b210. It is a 1500cc 4 cylinder and with the piston I will be using and the block 0 decked, we will be right up around 10:6:1 compression ratio. The engine will be spun to around 8200 rpm.
Currently, there are no .040" pistons available. A few sellers on ebay realize this and are selling these cast, 040's they have in stock for around 1k. Ring packs in the 500 dollar range : ( These pistons were going for under 100 bucks about 4 weeks ago, but they are all gone at this time (nissan ga16de)
what is available however, and on my bench at this time, is a 2 groove piston. One compression ring, and one oil control pack. Is this going to be an issue at these RPM's and cylinder pressures?
some modern 4 stroke motorcycle engines use 2 groove pistons, are high compression and spin 14k rpm (honda) food for thought. did I just answer my own question?
please advise speedtalk!
Pistons for those old Datsun/Nissan engines are easy to get in forged with any ring configuration you want.
I was doing lots of old Datsun stuff some years back for class racing and with the comp. rule they had it was money well spent just to get pistons from Diamond, JE/SRP or Wiseco. Then ring sets were not an issue and lateral gas ports were also an option for better ring seal as well making the builds much less work then to try locating stock type pistons to fill the bill to get the job done.
Re: single compression ring piston
Posted: Sun Feb 09, 2020 3:07 pm
by LSP
Mark O'Neal wrote: ↑Thu Jan 16, 2020 7:34 pm
All pistons have a single compression ring. The second ring is for oil control.
Are you sure? Saw this posted - saw this posted by, hmmmmm.... who was it?
"the function of the second ring is 20% compression control"
Re: single compression ring piston
Posted: Mon Feb 10, 2020 11:08 am
by engineguyBill
This ^^^^^^^ is correct. Most piston ring manufacturers define the second ring as 80% oil control and 20% combustion pressure control.
Re: single compression ring piston
Posted: Mon Feb 10, 2020 11:53 am
by LSP
engineguyBill wrote: ↑Mon Feb 10, 2020 11:08 am
This ^^^^^^^ is correct. Most piston ring manufacturers define the second ring as 80% oil control and 20% combustion pressure control.
Which piston ring manufacturers claim that the 2nd ring controls 20% of the combustion pressure?
Re: single compression ring piston
Posted: Mon Feb 10, 2020 12:28 pm
by mt-engines
engineguyBill wrote: ↑Mon Feb 10, 2020 11:08 am
This ^^^^^^^ is correct. Most piston ring manufacturers define the second ring as 80% oil control and 20% combustion pressure control.
I guess of the top ring isn't doing its job.
Oil control ring should then be called the blowby control ring.
I have run lots of 2 ring setups, and they do get more oil up top..
Re: single compression ring piston
Posted: Mon Feb 10, 2020 7:11 pm
by bentvalves
https://www.google.com/imgres?imgurl=ht ... gaegQIARB2
going to run a torsional in the top groove.
wish me luck. thanks for your input dudes.
Re: single compression ring piston
Posted: Mon Feb 10, 2020 9:46 pm
by engineguyBill
LSP wrote: ↑Mon Feb 10, 2020 11:53 am
engineguyBill wrote: ↑Mon Feb 10, 2020 11:08 am
This ^^^^^^^ is correct. Most piston ring manufacturers define the second ring as 80% oil control and 20% combustion pressure control.
Which piston ring manufacturers claim that the 2nd ring controls 20% of the combustion pressure?
All of them that I know of . . . . . . . . But you have misunderstood the statement. Second ring does not necessarily control 20% of the total combustion pressure, but rather the ring is designed as primarily an oil control ring (80% functionality) but also as a combustion pressure control ring (20% functionality). The second ring will help to control combustion pressure that is getting past the top ring via ring gap, etc. IF 20% of the combustion pressure is getting past the top ring, the engine has some serious issues.
Re: single compression ring piston
Posted: Mon Feb 10, 2020 10:46 pm
by Mark O'Neal
LSP wrote: ↑Sun Feb 09, 2020 3:07 pm
Mark O'Neal wrote: ↑Thu Jan 16, 2020 7:34 pm
All pistons have a single compression ring. The second ring is for oil control.
Are you sure? Saw this posted - saw this posted by, hmmmmm.... who was it?
"the function of the second ring is 20% compression control"
I'm sure. If your second ring is controlling compression, the top ring is not doing it's job.
Re: single compression ring piston
Posted: Mon Feb 10, 2020 10:47 pm
by Mark O'Neal
mt-engines wrote: ↑Mon Feb 10, 2020 12:28 pm
engineguyBill wrote: ↑Mon Feb 10, 2020 11:08 am
This ^^^^^^^ is correct. Most piston ring manufacturers define the second ring as 80% oil control and 20% combustion pressure control.
I guess of the top ring isn't doing its job.
Oil control ring should then be called the blowby control ring.
I have run lots of 2 ring setups, and they do get more oil up top..
I've always figured I can make more power with 3 rings than I can with oil in the combustion chamber.
Re: single compression ring piston
Posted: Mon Feb 10, 2020 10:53 pm
by Mark O'Neal
engineguyBill wrote: ↑Mon Feb 10, 2020 11:08 am
This ^^^^^^^ is correct. Most piston ring manufacturers define the second ring as 80% oil control and 20% combustion pressure control.
Even with increasing the second ring gap to bleed of pressure build up in the second land? Even with putting accumulator grooves in the second land to preclude pressure build up in the second land?
Maybe in 1990, but not anymore. Cast off the illusions of youth.......
Re: single compression ring piston
Posted: Tue Feb 11, 2020 5:52 am
by modok
Seems right IMO
Good luck
Re: single compression ring piston
Posted: Tue Feb 11, 2020 12:18 pm
by LSP
engineguyBill wrote: ↑Mon Feb 10, 2020 9:46 pm
LSP wrote: ↑Mon Feb 10, 2020 11:53 am
engineguyBill wrote: ↑Mon Feb 10, 2020 11:08 am
This ^^^^^^^ is correct. Most piston ring manufacturers define the second ring as 80% oil control and 20% combustion pressure control.
Which piston ring manufacturers claim that the 2nd ring controls 20% of the combustion pressure?
All of them that I know of . . . . . . . . But you have misunderstood the statement. Second ring does not necessarily control 20% of the total combustion pressure, but rather the ring is designed as primarily an oil control ring (80% functionality) but also as a combustion pressure control ring (20% functionality). The second ring will help to control combustion pressure that is getting past the top ring via ring gap, etc. IF 20% of the combustion pressure is getting past the top ring, the engine has some serious issues.
I don't want my second ring to EVER try to control any amount of combustion pressure, that's why every motor I build gets more second ring and top oil rail gap than the top ring does, some A LOT more.
Re: single compression ring piston
Posted: Tue Feb 11, 2020 8:51 pm
by engineguyBill
LSP wrote: ↑Tue Feb 11, 2020 12:18 pm
engineguyBill wrote: ↑Mon Feb 10, 2020 9:46 pm
LSP wrote: ↑Mon Feb 10, 2020 11:53 am
I don't want my second ring to EVER try to control any amount of combustion pressure, that's why every motor I build gets more second ring and top oil rail gap than the top ring does, some A LOT more.
You will be able to sleep peacefully knowing that your second rings will help control any combustion pressure that is getting past the top ring. And some combustion pressure WILL get past the top ring via ring end gap, piston rock, cross-hatch pattern, etc., etc. Engineering nomenclature, including manufacturing prints still refer to piston rings as top compression ring, second compression ring/oil scraper and oil ring assembly. The ability of the accumulator groove to function according to design is made possible by the second ring's ability to control combustion pressure.
