Piston design

[Steffen]

Found some old pistons that i have had for some years now. It got me thinking a bit.

Small engines has alwas had my intrests and have worked a lot on old Puch engines some years back. I have been running a lot of diffrent pistons to see the effect.

The 3 pistons on the picture are all for the same cylinder from a Puch. But as you can se there is big differens in them, both in hight and ring design.
The original piston is the one of the left and the one on the right is a L-ring piston with the one in the middel a combination of the two.

I have run the piston on the right a lot and it feels like it make a bit more compression in the cylinder and it revs faster. It also allow more fuel/air mix to pass under it from the inlet port.

The L-ring design has alwas been my favorite.

Do you know of any chainsaw piston to use this design?
It could be fun to see if it made a diffrens compared to a std. piston in chainsaws.

 

[zogger]

Subscribed, interesting question.

 

[1Alpha1]

Interesting thread.

Myself.....I prefer a two ring piston.

 

[blsnelling]

Why would you prefer two rings?

 

[1Alpha1]

Why would you prefer two rings?

Any "performance" gained (if any) by a single-ring piston is subjective at best, depending on who you are talking to.

For me, a two ring piston is far more likely to provide better durability and longer service.

 

[cuttinties]

Why would you prefer two rings?

Better heat distribution and piston stability.

 

[jughead500]

L or trapazoid rings were a big thing with wiseco back in the day.dont have chainsaw pistons but do have oversize one's for my suzukis.

 

[1Alpha1]

L or trapazoid rings were a big thing with wiseco back in the day.dont have chainsaw pistons but do have oversize one's for my suzukis.

Back in the day, the L-shaped rings were known as Dykes rings.

 

[jughead500]

Back in the day, the L-shaped rings were known as Dykes rings.

Yeap.haven't had the chance to try out a set.don't want to go 2+ mm out on a set of cylinders with a set of pistons without replaceable top rings. sucks because i have some stuff floatin' around in my head but one screw up and a lot of money is going to be shot. i can take my twin out from 492cc to 525cc or my triple to 780cc but if i'm going out with a bang i might as well go out with a big one.

 

[Brianlol]

Back in the day, the L-shaped rings were known as Dykes rings.

I like dykes too
Oh.... What r we talking about

 

[jughead500]

I like dykes too
Oh.... What r we talking about

Dykes don't like you though.

 

[1Alpha1]

My experience with a Wiseco piston with a single Dykes ring was not positive. It was for my 1972 TM-4ooR Suzuki Cyclone.

The ring last about two months before I went back to an OEM two ring piston.

 

[jughead500]

Thats what i'm afraid of in a gt 750 or t500 could become a serious lesson learned on the bank accout these days.if i'm going that ay i'm going with a port job and reeds along with the wiseco's.

 

[jughead500]

Oh and as far as dyke's rings as far as i know wiseco my havemade some for mcculloch go carts back in the day which would have crossed over to the saws BUT what do i know i'm just a kid that likes old toys.i'm sure some of the older Mac guys might fill you in.

 

[burnses]

having the top ring close to the top of the piston is a gain in performance I think because of the marginal compression gain but also eliminates increased volume that air fuel and hide in and note get burned.......think of it as a horizontal squish band with the ring far down the piston...

 

[Brianlol]

Jealous

 

[Steffen]

I have looked a bit in to the design. The upper L ring bette block bypass gasses and hold the compression better. It seems that the compression presses the ring harder out against the cylinder wall. Therefore it makes the engine revs faster and have higher output than the regular piston ring design.

Piston design like the one at the right in the picture, the one L-ring hold the compression better than the one in the left that has two normal rings. Problem is that the piston/ring wear out faster.

This could be harder on the ring and cylinder and the life of the components would be shorter. This might be the reason this design is only used on race engines.
The design also keeps the tempature in the piston a bit lower at full revs.

 

[Steffen]

There is pdf papir about the Dykes ring design on this site if anyone would like to read a bit about it:

http://www.bridgestonemotorcycle.com/documents/l-ring_effect6.pdf

And look at this thread about the Stihl 090 10cube... It has the dykes ring ;-)

http://www.arboristsite.com/communi...e-to-see-a-new-stihl-090-10-cube.98525/page-4