Single ring V.S. double ring pistons

[bwalker]

As has been mentioned the rings are the main path that heat follows out of the piston.
I suspect that when the 372 was EPA certified a 2 ring piston was needed to deal with the extra heat generated.
IMO and IME single ring pistons do not last as long as double ringers. I own saws with both.

 

[SawTroll]

...
I suspect that when the 372 was EPA certified a 2 ring piston was needed to deal with the extra heat generated. ...

That seems plausible, as the 372s are reported to still have only one ring over here.

 

[Lakeside53]

While on this topic...

The 088 piston has a cast iron disk inserted into the crown of the piston just above the top ring. It protrudes from the side of the piston, has a tight bore fit, but it's not a "flexible ring".

It performs two functions:

- protects the top ring from the direct combustion burn (directed down between the side of the piston and bore.

- Modifies the thermal path so the very hot top of the piston and the "cold" underneath are somewhat isolated (the heat now spreads across the crown evenly) and lets the rings preform heat transfer more efficiently.

Aftermarket pistons being sold cheaply for the 088/084 are just over-sized regular aluminum alloy pistons - they don't have the heat disk. If you are going to buy a Ebay 084/88 and it says "new piston" ask the right questions... or you'll end up with a short piston life or even a hole in the top of the pistons.

 

[MEANHUSQVARNA]

Ej

Got A Question For You Lakeside Or Anybody Do You Have A O90 For Sale Did You Know They Made A 10cube O9o And They Still Make The 090 In Germany

 

[Lakeside53]

I don't have one for sale, but know of a couple for Contra Lightnings for sale.

The 090 is no longer made. The 070 (same, but smaller piston/cylinder) is still made in Germany for South America/Asia only.

 

[MEANHUSQVARNA]

Ej

Lakeside Cliff Hughs Of New Zealand Brought Over To America Was A 10 Cube 090 I Looked At The Saw With The Cylinder Off 70mm Bore With 40mm Stroke And The Regular 090 Was 40mm Stroke And 66mm Bore Rolin Eslinger Bought It From Cliff Hughs :d

 

[Dennis Cahoon]

Mean.....Wayne Sutton from Amboy, WA. bought that saw from Rolin 6 or 8 years ago. It had a removable head and had a bigger bore than the 090. (somewhere around 10cube) I know this for a fact because I had the saw at my place and took the head off. Ace Morgan had ported boost ports in the cylinder. I had Wayne's # but can seem to find it. Many someone on the site has it. Give him a call. He's a Stihl rep too, so you might be able to get his # thru Northwest Stihl in WA. Later Dennis

 

[SawTroll]

.... The 070 (same, but smaller piston/cylinder) is still made in Germany for South America/Asia only.

That was new info; I thought the current 070s were made in Brazil.

 

[Lakeside53]

That was new info; I thought the current 070s were made in Brazil.

Nope... Sometime ago I published a link that showed (in Spanish) that they were made in Germany. I confirmed this with Stihl - they have a small group of guys that just make a limited number each day.

 

[buck futter]

Wow,thanks

Lake,
Just when I thought I knew everything you burst my bubble.


Hahaha

Thank you,
That was very informative. I like being wrong in that it means I learned something. I appreciate that you didn't just give up on me and you eloquently made your point.

Thank you

Buck

 

[Lakeside53]

Lake,
Just when I thought I knew everything you burst my bubble.


Hahaha

Thank you,
That was very informative. I like being wrong in that it means I learned something. I appreciate that you didn't just give up on me and you eloquently made your point.

Thank you

Buck

"Doubting Thomas's" make me better at what I do!!! Heck I had to really think about it... it was like you said "prove to me chocolate is as good as sex" .... tough..


Keep asking.. you'll catch me out yet, then I'll learn, again..:rockn: :rockn:

 

[SawTroll]

Nope... Sometime ago I published a link that showed (in Spanish) that they were made in Germany. I confirmed this with Stihl - they have a small group of guys that just make a limited number each day.

Thank you Lakeside, that was interesting info!

It adds up too - it has puzzled me that they have been on the Mexican web-site, but not on the Brazilian one....

 

[slipknot]

What current saws use the single ring design?

 

[Lakeside53]

I'll answer only the the Stihl question.

0

 

[slipknot]

That was all informative but i got a new question to add to the mix.

Q.) Are double ring pistons more prone to scoring and siezing because of more friction?
I just had a double ringer sieze up on me even though I used premium gas & oil(non-ethanol 93 & Mobil 1 mxt2 @ 40:1) This was a fairly new saw(less than 4 gal of uel thru it) I have been on this site for a couple years now so I Know what a lean seizer is and i know the saw wasn't running to lean.

 

[Woodie]

So... is one thick ring better than two thin rings? I doubt it... Not many saws made with one ring now, so there must be a reason.

All due respect, but can't agree with you at all here, Lakeside. All the Dolmars except one, and all the Husqvarnas from 362 on down are all one ring (including the 570). Some pretty well-respected saws in there...the 338/346/353/359/357, the PS5100S, 7900.

 

[Ombesb]

If I may jump in here, there is another little thought about rings that I became aware of years ago. Heavier [thick] rings would do what is called 'ring flutter' at a relatively low rpm. A small block chevy could do that at around 7500~ 9000. As best I understand it, the piston is dragging the ring up the cylinder, when it stops at the top the rings sort of slams into the top of the groove. This is exacerbated at very high rpm. The rings then bounces off of the bottom of the land and so on. [flutter] By going to thinner rings , less weight, rpm levels could be moved up. So by going to 2 lighter rings there could be higher rpm levels available. Possibly related to upping rpms in smaller saws for more hp. There is also a more complicated path for blowby past the ring gaps. Possibly to do with emissions more than anything else. Just a few thoughts.

 

[Donny Thompson]

A single ring piston will have peak performance quicker than a 2 ring piston but a 2 ring piston will last longer durability wise.

 

[Lakeside53]

All due respect, but can't agree with you at all here, Lakeside. All the Dolmars except one, and all the Husqvarnas from 362 on down are all one ring (including the 570). Some pretty well-respected saws in there...the 338/346/353/359/357, the PS5100S, 7900.

Do they last 2000 hours? Rhetorical question, 'cos I have no idea... Seems to me that a single ring is an easy way to get low friction and immediate gains, but there is a penalty to pay in terms of longevity. opcorn:opcorn:opcorn:

Who dragged up this old thread anyhow?:hmm3grin2orange:

 

[slipknot]

Do they last 2000 hours? Rhetorical question, 'cos I have no idea... Seems to me that a single ring is an easy way to get low friction and immediate gains, but there is a penalty to pay in terms of longevity. opcorn:opcorn:opcorn:

Who dragged up this old thread anyhow?:hmm3grin2orange:

I did! i gotta question somewhere up there^