Hyway MS460 big bore on a 044 opinions please

[mdavlee]

If you could get 210 and exhaust at 95 that's where I would go.

 

[drf256]

And the great debate rages on...
I was considering 225. That should allow wiggle room to open the chamber if it is too much.

Is anyone running more than 220 in gtg saws of this model? Just looking for max grunt without wasting power/rpm. Im not worried about wear and tear. This will not be a daily driver
All my jugs are round chamber.

I’m talking worksaws Ken. I do believe most race saws don’t run a ton of compression.

At least for me, higher compression saws have had more low end grunt but didn’t spool up as fast or 4 stroke as high as lower compression saws. At some point, it starts to rob more power than it makes. The part I dislike about too much comp is that it builds heat faster. Come out of a long cut with a 250 psi saw, and the saw will be leaner than a 200 psi one.

Bigger chambers can’t get rid of heat as fast as smaller ones.

@Stihlbro , any comments?

 

[Stihlbro]

And the great debate rages on...
I was considering 225. That should allow wiggle room to open the chamber if it is too much.

Is anyone running more than 220 in gtg saws of this model? Just looking for max grunt without wasting power/rpm. Im not worried about wear and tear. This will not be a daily driver
All my jugs are round chamber.

You can get by with more compression for a gtg saw, as it is typically short run times. Which version of the 460 jug you use can determine the outcome. I like the 064 piston idea.

 

[MustangMike]

You can also space the cylinder up depending on your #s.

 

[Lightning Performance]

If you could get 210 and exhaust at 95 that's where I would go.

Your floating on my cloud. I can get there and keep transfers in check.

I’m talking worksaws Ken. I do believe most race saws don’t run a ton of compression.

At least for me, higher compression saws have had more low end grunt but didn’t spool up as fast or 4 stroke as high as lower compression saws. At some point, it starts to rob more power than it makes. The part I dislike about too much comp is that it builds heat faster. Come out of a long cut with a 250 psi saw, and the saw will be leaner than a 200 psi one.

Bigger chambers can’t get rid of heat as fast as smaller ones.

@Stihlbro , any comments?

If you last sentence holds true good. I want to run a tiny but wide chamber with the narrowest band possible. I can get there to.

You can get by with more compression for a gtg saw, as it is typically short run times. Which version of the 460 jug you use can determine the outcome. I like the 064 piston idea.

460 round or am bb round. I dont like the 064 piston. Too heavy and one too many rings on it.

You can also space the cylinder up depending on your #s.

Yup. Sure can with the right piston.


My take here is I can jack the exhaust up ten degrees if needed. The chambers getting closed.

 

[mdavlee]

52mm. I think Copsey may have a good 54mm.

 

[Lightning Performance]

Yikes. I wont ask.

You smell that?

 

[MattG]

I think Copsey may have a good 54mm.

So what standard engines (not particularly choosy on manufacturer) sport 54mm, and 12mm pins?

Ideally with between 0.609" - 0.629" pin to crown

046 pin to crown

as that is what I've been after throughout all this thread!

 

[MattG]

I've just checked the 056 super. Groan. 54mm bore, but 13mm pin

What about Jonsered or Dolmars? Anyone know of any of the bigger models of those?

 

[Lightning Performance]

For now 064 shed the ring. Or just run the 460 piston in my case. I'm closing the chamber and considering a taller piston cut down to a pop up. Mike says a hundred off should be ok. Three spend more money go Weisco.

 

[Lightning Performance]

I've just checked the 056 super. Groan. 54mm bore, but 13mm pin

What about Jonsered or Dolmars? Anyone know of any of the bigger models of those?

Makita 8400 kit too short.

 

[drf256]

Have you looked at the dominant website?

https://dominantsaw.com/products/dominant-wiseco-50mm-piston-for-stihl-ms460

They’re making a new domed 52mm piston. Flat on edged with central dome.

As for 54mm with 12mm pin, Stihl 066.

 

[drf256]

You can also space the cylinder up depending on your #s.

Putting a big spacer under a 54mm big bore 046 jug and an 066 slug will add the much needed case volume to make it a runner.

BTW,

Are we considering Wiseco and Dominant Saws parts aftermarket for the MS440 build off?

 

[Fruecrue]

Putting a big spacer under a 54mm big bore 046 jug and an 066 slug will add the much needed case volume to make it a runner.

BTW,

Are we considering Wiseco and Dominant Saws parts aftermarket for the MS440 build off?

Last year, I believe you had to run the piston that came with whatever cylinder you chose in classes 1 & 2.
If my interpretation is accurate, and no Changes have been made, I believe that would put you in class 3.

 

[MattG]

You can also space the cylinder up depending on your #s.

Putting a big spacer under a 54mm big bore 046 jug and an 066 slug

Ahh.....I see. I guess you guys have probably given me enough hints by now!


So I get 1.5mm of alloy plate, use a gasket as a template, and cut me a spacer.

Now since the slug's about 1.5mm higher from the pin but the jugs raised similarly, my timing numbers for exhaust and transfers should remain in the same ball park? Then I'll need to pay attention to remove metal potentially from the intake floor to adjust for the inlet opening....Hmm...This seems like it may have wings

add the much needed case volume to make it a runner.

Ahh... the penny is starting to drop now (I think). So the reason the 044/460 is so high revving is because the higher case compression means the cylinder is purged so damn well that it can spin very fast before it runs out of breath?

Therefore, the (noted) increase in case volume, should hopefully bring a 460BB on a 044, back to something a little bit more like a regular 44/46 hybrid?

 

[MustangMike]

You can also adjust the intake by taking some off the bottom of the piston, and you don't have go go all the way across, just some in the middle. Keeps the piston more stable.

 

[drf256]

Ahh.....I see. I guess you guys have probably given me enough hints by now!


So I get 1.5mm of alloy plate, use a gasket as a template, and cut me a spacer.

Now since the slug's about 1.5mm higher from the pin but the jugs raised similarly, my timing numbers for exhaust and transfers should remain in the same ball park? Then I'll need to pay attention to remove metal potentially from the intake floor to adjust for the inlet opening....Hmm...This seems like it may have wings


Ahh... the penny is starting to drop now (I think). So the reason the 044/460 is so high revving is because the higher case compression means the cylinder is purged so damn well that it can spin very fast before it runs out of breath?

Therefore, the (noted) increase in case volume, should hopefully bring a 460BB on a 044, back to something a little bit more like a regular 44/46 hybrid?

I could be talking out of my arse, but here’s what I’ve observed. I hope someone corrects me if I’m wrong.

It seems that these little 2 strokes will only flow so much air, and the bottle neck for flow is likely the carb Venturi, Muffler vent and transfers.

There’s an ideal case volume/displacement ratio which escapes me at the moment.

So let’s say the max an engine will flow by port/venturi/outlet is 100 cfm. If your case capacity is 1 cubic foot, your engine will turn at 100 rpm to move that max amount of air. Now put a full circle crank or anything else that reduces case volume on the saw and reduce case volume to 1/2 cubic foot. The motor will be able to turn 200 rpm to move the max 100 cfm. See where I’m going here?

So an engine will take more smaller gulps to move the same max flow which equals more rpm.

I haven’t measured case volume on an 044 vs 046, but if the 044 is 10% less, it should make 10% more rpm than it’s larger cased counterpart. That pretty much what happens with these hybrids. They typically run at 15000 and their 046 cased counterparts run at 13500-14000.

 

[mdavlee]

1.5:1

 

[MustangMike]

Good stuff Al. I guess the big questions is can a different porting style (#s and/or port size/shape) maximize the effectiveness of different displacement to case volume scenarios???

I'd also like to see some tests that reflect the effect of different timing mods. Specifically, does more timing put peak Hp at a higher RPM, and is this at the expense of lower end torque?

Guess we have to get Bill and Eric back on that dyno project!!!

 

[MattG]

I could be talking out of my arse,

Definitely not in my opinion!

There’s an ideal case volume/displacement ratio which escapes me at the moment.

So let’s say the max an engine will flow by port/venturi/outlet is 100 cfm. If your case capacity is 1 cubic foot, your engine will turn at 100 rpm to move that max amount of air. Now put a full circle crank or anything else that reduces case volume on the saw and reduce case volume to 1/2 cubic foot. The motor will be able to turn 200 rpm to move the max 100 cfm. See where I’m going here?

I see it slightly differently. Basically if an engine is not held back it's carburretion or it's ignition, then the only (?) thing holding it back, i.e. preventing it from revving higher, is how effectively it can flow a dense charge into the CC.

For the reasons you pointed out (muffler, transfers, venturi, etc.) the engine will "run out of breath" at a particular ceiling (i.e. 14 or 15k or whatever). However, by increasing the case compression, I believe that we create a supercharging effect, enabling the system to rev somewhat higher than before.

Well that's my take on things