ms 461 woods port race thing

[Keith Gandy]

It doesn’t show what you are looking for... I think it clearly shows how I think it goes... [emoji6]
but again, not enough info to be definitive.

Lets look at it this way Dan, if z is pointing toward exhaust as u say and x toward the transfer which would be the flywheel side, in the orange thermo there is more orange wrapping almost halfway around on the PTO side than to the flywheel side? See the larger blue/cooler transfer side to the flywheel side vs the smaller /blue cool area on the PTO but more orange wrap around to the PTO? Thats what Im seeing with the oreintation as u described

 

[paragonbuilder]

Lets look at it this way Dan, if z is pointing toward exhaust as u say and x toward the transfer which would be the flywheel side, in the orange thermo there is more orange wrapping almost halfway around on the PTO side than to the flywheel side? See the larger blue/cooler transfer side to the flywheel side vs the smaller /blue cool area on the PTO but more orange wrap around to the PTO? Thats what Im seeing with the oreintation as u describedView attachment 106889 View attachment 106890

Yep, ok, I see that, but you are assuming that this engine is oriented like our saws. I see nothing that shows which side is flywheel and which is pto.
Even if it is, I’m not sure it’s enough to change the wash patterns.
But you can be sure I will be paying attention to this on every 2 stroke I open up now.
And if I’m wrong, great, I’ll have learned something, but I won’t just believe it cuz someone thinks so. Nothing personal.
Thanks for digging up those pics. They aren’t conclusive enough for me, to many unanswered questions. But if you find more please bring them out.

 

[laslabjohn]

Lets get back to this saw fellas before it gets all messed up.. this coukd be a topic on its own.

 

[paragonbuilder]

Perhaps we should start a thread on it. We’ve sufficiently derailed Scott’s 461 R&D thread...[emoji23]

 

[P.M.P.]

Farkin Golf Balls

 

[Keith Gandy]

Lets get back to this saw fellas before it gets all messed up.. this coukd be a topic on its own.

This could go hand in hand with what Scott is going for here. Maybe so maybe not. Im sure he already knows the anwser to our debate

 

[maulhead]

Lets get back to this saw fellas before it gets all messed up.. this coukd be a topic on its own.

Here, here, you tell em Bubba, tell em to put the crayons away, before they all get eaten.

WTF, is wiff the color charts anyways....

 

[XP_Slinger]

This could go hand in hand with what Scott is going for here. Maybe so maybe not. Im sure he already knows the anwser to our debate

While it is interesting, Scott was trying to stop the primary charge from walking out the exhaust port to the extent that it is. Don’t really think the heat discussion applies to this issue. I think a separate thread would be great to continue the heat discussion as it is really an animal all unto itself.

 

[Moparmyway]

View attachment 106784

I made a port map that I used to mark the port locations onto the piston. mark to ex port on the piston while on the saw to get it oriented

The secondary ports look different from each other

well maybe not. there is a divider in there

It’s down in the runner a little, about midway between the uppers and lowers


I’ve been catching up on this thread, actually have been excited to see the next post, then the next, and so on !!

I agree 100% with Doc, this kind of testing and posting about it has made this thread the best one that I have ever had the privilege to read

Great work Scott, and thank you Sir !!!

 

[CR888]

Damn thermo-graph! We were being priveliged to see proper 2T tuning in action, then the thermo-graph was posted. I wanna set the thermo graph a light and watch it burn.

 

[bryanr2]

a little more ex timing

I got a little chuckle out of this..... No slight to you Scott, merely the similarity of running a saw indoors.
makes me think of that ol fella over on AS that used to run his in the garage..... name slips me though. We used to harp on him pretty good. His name was Dan something, maybe Dano?

Beyond that, Scott I really appreciate all your knowledge that you share with the forum, its a contribution that can't be measured in my opinion.

 

[Terry Syd]

Perhaps to minimize the short-circuiting there can be a combination of things used - port and piston top.

When the cylinder is dropped, the transfers will likely get raised back up some. That leaves some leeway in NOT raising the corner of the primaries nearest the exhaust port. By delaying the front part of the primaries a bit, it allows the blow-down to have more affect on the cylinder exhaust flow before the front part of the primaries opens. It also gets the transfer flow moving so that when it does open it wants to continue in the same direction.

In conjunction with that mod, the piston can be notched on the top to open the 'back' part of the primary port first. A rather steep slope could be cut into the piston top that may not be able to be reproduced in the actual cylinder transfer roof. The notch in the piston crown also provides a mechanical dam to flow towards the exhaust port.

There's not much room between the primaries and the exhaust port, but the above mods could correct the short-circuiting.

 

[Terry Syd]

Here's another trick that might work - a notched exhaust port. On some two-strokes, like my Victa lawn mower, the exhaust port has an exhaust port where the center of the port has a 'channel' that opens way before the rest of the exhaust port.

This type of exhaust port is usually done to reduce the noise of the exhaust. It works well to keep not only the initial blast from the exhaust from making noise, but it also helps trap the incoming intake mixture.

In the first part of the exhaust cycle the pressure differential is the highest. It has been estimated that the first 10% of the exhaust port opening does most of the work in dropping the cylinder pressure. So, the 'channel' drops the pressure, and then the rest of the exhaust port opens and provides an easy flow when the transfers open.

It may be that an exhaust port where the center of the port opens, perhaps 1/2 of the port width (or more), drops the pressure and then the remainder of the exhaust port opens later to provide an easy flow of the transfer. That would likely help to reduce the short-circuiting in this jug.

 

[Keith Gandy]

Here's another trick that might work - a notched exhaust port. On some two-strokes, like my Victa lawn mower, the exhaust port has an exhaust port where the center of the port has a 'channel' that opens way before the rest of the exhaust port.

This type of exhaust port is usually done to reduce the noise of the exhaust. It works well to keep not only the initial blast from the exhaust from making noise, but it also helps trap the incoming intake mixture.

In the first part of the exhaust cycle the pressure differential is the highest. It has been estimated that the first 10% of the exhaust port opening does most of the work in dropping the cylinder pressure. So, the 'channel' drops the pressure, and then the rest of the exhaust port opens and provides an easy flow when the transfers open.

It may be that an exhaust port where the center of the port opens, perhaps 1/2 of the port width (or more), drops the pressure and then the remainder of the exhaust port opens later to provide an easy flow of the transfer. That would likely help to reduce the short-circuiting in this jug.

Terry woud it have to be a notch or would a steeper arch in the middle work? Too steep probably hard on the rings?

 

[Terry Syd]

I don't know what might work. However, if you had a piston to start trimming on, you may be able to find something that works. Start trimming the piston in the middle of the exhaust port and work out and up.

You might end up with a 'two-stage' port roof for the exhaust that eliminates the 'short-circuiting' and allows for good all around power ON THIS JUG. The bottom line for modding is - "what works is just that - WHAT WORKS!"

 

[Keith Gandy]

I don't know what might work. However, if you had a piston to start trimming on, you may be able to find something that works. Start trimming the piston in the middle of the exhaust port and work out and up.

You might end up with a 'two-stage' port roof for the exhaust that eliminates the 'short-circuiting' and allows for good all around power ON THIS JUG. The bottom line for modding is - "what works is just that - WHAT WORKS!"

Tuned muffler may work the same?

 

[maulhead]

 

[Terry Syd]

Tuned muffler may work the same?

Nope, if you are referring to tuning the exhaust pulse, then a strong pulse is the best to work with. On a can muffler, we can't tune the pulse.

What we are looking for on this jug is a way to avoid the short-circuiting of the intake mixture from the transfers. It may be that a two stage opening (so that the flow stays in the center of the cylinder) doesn't affect the flow coming out of the primary transfer port. I don't know if it will work, it is one of those things that can be tried. If it works - it works.

 

[Moparmyway]

Nope, if you are referring to tuning the exhaust pulse, then a strong pulse is the best to work with. On a can muffler, we can't tune the pulse.

What we are looking for on this jug is a way to avoid the short-circuiting of the intake mixture from the transfers. It may be that a two stage opening (so that the flow stays in the center of the cylinder) doesn't affect the flow coming out of the primary transfer port. I don't know if it will work, it is one of those things that can be tried. If it works - it works.

It’s my understanding that the most power is made with the exhaust roof being as flat as can be, opening all at once. The arched roof that we normally aim for is for ring durability. There’s usually no way of avoiding a tradeoff when changing the way the exhaust opens. Asking the exhaust to open in two stages might help the short cycling, but it could also cause the saw to drop power.

 

[Terry Syd]

You can even IMPROVE on the flat roof by having a curved roof. All you have to do is trim the top of the piston to match the curved roof. A straight line is the shortest distance between two points - if you take a curved line between the two points, you INCREASE the distance between the two points. - In other words, you increase the size/length of the opening when it first opens.

That will give you an even stronger pulse to work with in an expansion chamber. However, we are trying to eliminate the short-circuiting on this jug, which is entirely a different problem.

We aren't working with an expansion chamber and tuning the exhaust, we are working with FLOW. We need to correct the flow so that the intake mixture stays in the jug to be burned.