1 or 2 piston rings?

[Lakeside53]

The only 2 Stihl products I ever seen with 1 ring was a 015 and a FS36 (line trimmer)
I think the idea is one ring offers less friction which reduces heat. Two rings seal better. Old 3 ring seal best but alot of power lost to friction. Which is better, ?

The rings take the combustion heat from the piston to the cylinder wall...

 

[stihl86]

Two piston rings create more friction than one was my point.

 

[Lakeside53]

Maybe... but they remove a lot more heat than they produce.

 

[SawTroll]

Two piston rings create more friction than one was my point.

..which means more heat to transfer - no conclutions here, except that one ring likely will break in faster than two (fits well with my experience).

 

[stihl86]

Yet the question is still unanswered. Different designs that produce the same results.

 

[SawTroll]

Yet the question is still unanswered. Different designs that produce the same results.

Right, I leave the 1 vs. 2 rings totally out of the equation, when considering what saw to get......

 

[Jacob J.]

Yet the question is still unanswered. Different designs that produce the same results.

I like to think that Stihl engineers know what they're doing...after all, most of them have Masters and Doctoral degrees in engineering, and we're a bunch of schmucks making comments on the internet...Also it's funny how Husqvarna went from the one-ring to the two-ring design in all of their big pro saws...

 

[romeo]

I prefer single ring pistons in race saws, but only for porting reasons. The dfferences are very small for torque vs hp.

 

[SawTroll]

Funny how I cut more timber in a day with my two-ring 372 than guys cutting right next to me with their single-ring 371s...

I like to think that Stihl engineers know what they're doing...after all, most of them have Masters and Doctoral degrees in engineering, and we're a bunch of schmucks making comments on the internet...Also it's funny how Husqvarna went from the one-ring to the two-ring design in all of their big pro saws...

The 372xp still is single-ring here, I believe - I also believe it was a massive adverisement campaign by Stihl some years ago (about that issue) that made them change to two rings on the US market - not that it really is a better solution - but then again, what do I know............: :

Btw, I have seen Husky referring to the two ring pistons as "EPA" versions.

 

[liberty]

I have a 372 XPW. Does it have one ring or two?

 

[Jacob J.]

I have a 372 XPW. Does it have one ring or two?

Two rings. There was also a triple thin-ring piston made as a prototype for the 394...but we're not supposed to know about that.

 

[Adirondack]

Do all Dolmar's have one piston ring?

 

[Jacob J.]

The 510, 5100, 6400, 7300, 7900 have one ring- the 9010, PS-520, 540, and 6800 all have two.

 

[SawTroll]

The 510, 5100, 6400, 7300, 7900 have one ring- the 9010, PS-520, 540, and 6800 all have two.

Meaning the older designs have two, and the newer ones one..........:biggrinbounce2:

 

[Tzed250]

1 ring designs are for those that like to replace top ends more often... :deadhorse:

 

[Trigger-Time]

The 510, 5100, 6400, 7300, 7900 have one ring- the 9010, PS-520, 540, and 6800 all have two.

Meaning the older designs have two, and the newer ones one..........:biggrinbounce2:

Just like most other things,.........just keep getting made cheaper .

 

[harrygrey382]

Just like most other things,.........just keep getting made cheaper .

yep - the usual story

 

[Crofter]

1 ring designs are for those that like to replace top ends more often... :deadhorse:

Well it looks like that may be correct. I posted on the other old one ring vs two ring thread (which I bumped up) that a certain cutter had put high hours production cutting on a number of different saws with one and two rings and found little difference.
Well, my memory was wrong. I contacted him today to verify and he said the two ring ones lasted longer by quite a bit.

 

[scotclayshooter]

Well it looks like that may be correct. I posted on the other old one ring vs two ring thread (which I bumped up) that a certain cutter had put high hours production cutting on a number of different saws with one and two rings and found little difference.
Well, my memory was wrong. I contacted him today to verify and he said the two ring ones lasted longer by quite a bit.

I can belive they last longer but i bet cost wise to those of us that can change a ring out ourselves it will make NO differance!

 

[kgb007stb]

I asked the same question a while back and the replies boiled down to:
1 ring – tighter tolerances,
2 rings – looser tolerances, thus two rings to stabilize the piston,

and I forget which one was more efficient at heat transfer.