Upper transfer angles

[drf256]

Some questions on what your thoughts are on upper transfer opening angles.

I'm referring to the degree that the opening in the plating occurs. We'll hopefully discuss entry angles later.

I've only played with 2 port motors. I hope to do my first quad soon.

So on a 2 port motor, I've been opening them squarely. I've experimented with opening them at a smooth angle that opens them at 1-2* sooner on the intake side. I've also done what I called a "minifinger" (for lack of any other way to describe it) where I opened 2-3* sooner with a defined wing off of the upper heading towards the intake. I did this on a 262XP and it only has 12* of blowdown at the minifingers.

I haven't done any timed trials with this, though I should. It would be easy enough to keep raising the transfer.

I'm wondering if I'm creating a situation where the exhaust is blowing down the lip and changing the transfer spray pattern. I'm also wondering if I can use this effect to my advantage-I'm wondering if a higher placed opening on the exhaust side of the upper can push the charge more forward to creat a better scavenging loop.

Anyway, here's a pic of my 262 uppers.

I'd like a discussion on thoughts for the above.

 

[Deets066]

That's a good question. I see it often when stock, they open sooner on intake side by a couple degrees.

 

[drf256]

This saw is pulling 237psi compression and isn't broken in yet. I'm hoping it doesn't climb much higher.

The decomp pops after the first compression cycle on the pull.

It's on its second starter cord, already.

 

[Moparmyway]

I'm wondering if a higher placed opening on the exhaust side of the upper can push the charge more forward to creat a better scavenging loop.

My thought is that most of an exhaust side placed finger, or lower transferr lip will end up going right out the exhaust. At the point in which any of the transferrs open, there is a very strong flow of exhaust gasses moving out of the cylinder and into the muffler. I think the transferr from an exhaust side finger or lower transferr lip would just enter into this "stream" and most of it would exit along with it.

I believe you would get a more efficient "push" if you fingered from the intake side

This is NOT to say that I know what I am speaking of, its just theory in my mind.

 

[drf256]

That's a good question. I see it often when stock, they open sooner on intake side by a couple degrees.View attachment 486

Yeah, a billion dollar company's engineers must know something.

 

[Moparmyway]

This saw is pulling 237psi compression and isn't broken in yet. I'm hoping it doesn't climb much higher.

The decomp pops after the first compression cycle on the pull.

It's on its second starter cord, already.

Remove the decomps and throw them into the trash, or give them to the drawer for stock replacements.
Decomps have no place on higher compression saws, they will just close mid stroke, bloody your knuckles, and eventually leak

 

[drf256]

My thought is that most of an exhaust side placed finger will end up going right out the exhaust. At the point in which any of the transferrs open, there is a very strong flow of exhaust gasses moving out of the cylinder and into the muffler. I think the transferr from an exhaust side finger would just enter into this "stream" and most of it would exit along with it.

I believe you would get a more efficient "push" if you fingered from the intake side

This is NOT to say that I know what I am speaking of, its just theory in my mind.

No answer is wrong here. Discussion of theory is what I'm interested in. A bunch of others too.

Hoping this place ain't like AS-where a bunch will start fights out of grudges and insecurity.

 

[drf256]

On quad motors, stihl opens the transfers like a "V" if you peer down the cylinder.

The exhaust lip opens first, followed by the intake lip, then the rest.

So it looks like a "V" with a shorter line on the right side.

 

[Moparmyway]

On quad motors, stihl opens the transfers like a "V" if you peer down the cylinder.

The exhaust lip opens first, followed by the intake lip, then the rest.

So it looks like a "V" with a shorter line on the right side.

Hmnnn ..............
I thought I noticed my 661 quads were leaning to the intake.
Have to look again

 

[Moparmyway]

I didnt do anything to the transferrs but clean up some casting flash

 

[Deets066]

In any of the saws I've ported, which is only a few. I've opened the transfers flat across. When people talk about adding fingers they say to open them 2 degrees sooner. So, I believe you could have the same affect by angling the uppers. But won't this give you less time/area at a given duration?

 

[Moparmyway]

In any of the saws I've ported, which is only a few. I've opened the transfers flat across. When people talk about adding fingers they say to open them 2 degrees sooner. So, I believe you could have the same affect by angling the uppers. But won't this give you less time/area at a given duration?

So you grind the exhaust side of the transferr more, enabling it to open at the same time as the intake side ?

 

[Stihlbro]

Good question drf255, I've have yet to see a Stihl that did not have a factory different transfer opening side to side. I believe it is there for a reason. To answer your question, I have tried 90 degree opening, 45 degree, used ball ends, Christmas tree burrs, staggered front to rear, even tried a two stage opening(by accident, darn high speed sharp tools) experimenting. Here is my conclusion, I have found my self making other changes with porting, so I never know if what I tried on transfers worked. I can see where a taper towards intake could actually pressurize the cc and effectively blow more fresh charge once exh pressure is less than transfer charge. Looking at a 2 port motor, following the transfer back wall, I see transfer tunnels would be like electricity that they will flow the path of least resistance. Good to see someone else thinking out the box and willing to try new stuff.

Have you looked at a 361 cylinder yet? A lot going on there. I'll talk more later.

 

[mdavlee]

Oem husky cylinders have the primary flat and secondary on an angle.

 

[Moparmyway]

Oem husky cylinders have the primary flat and secondary on an angle.

Primary being intake ?
Secondary being exhaust ?

 

[mdavlee]

Primary being intake ?
Secondary being exhaust ?

Backwards

 

[Moparmyway]

Backwards

So the husky transferrs look like the picture of the 661 transferrs ............. intake side angled for earlier opening ?

 

[drf256]

Good question drf255, I've have yet to see a Stihl that did not have a factory different transfer opening side to side. I believe it is there for a reason. To answer your question, I have tried 90 degree opening, 45 degree, used ball ends, Christmas tree burrs, staggered front to rear, even tried a two stage opening(by accident, darn high speed sharp tools) experimenting. Here is my conclusion, I have found my self making other changes with porting, so I never know if what I tried on transfers worked. I can see where a taper towards intake could actually pressurize the cc and effectively blow more fresh charge once exh pressure is less than transfer charge. Looking at a 2 port motor, following the transfer back wall, I see transfer tunnels would be like electricity that they will flow the path of least resistance. Good to see someone else thinking out the box and willing to try new stuff.

Have you looked at a 361 cylinder yet? A lot going on there. I'll talk more later.

No, I haven't seen a 361 yet. I do have a 362 on my bench though.

Very interesting. I'm trying to limit this discussion to the opening in the plating.

Next, I'd love to discuss entry angles of the aluminum before it hits the plate. I have some theories on that as well. I feel that a flat entry on the exhaust and an upward angle towards the intake, with a slow ramp up, would purge gasses the most efficiently. The problem is that you need to epoxy the exterior upper transfer edge to carve it in. I plan to do this on an 026 jug. I was also thinking of keeping a central lip, like the one that sometimes goes down into an intake port on some saws, for ring support and widening the uppers. So there would be a partition and keep ring suport allowing me to widen the uppers.

 

[mdavlee]

So the husky transferrs look like the picture of the 661 transferrs ............. intake side angled for earlier opening ?

No the upper is tilted up on entrance. I'll go grab a picture in a minute.

 

[drf256]

View attachment 488
I didnt do anything to the transferrs but clean up some casting flash

Put a ring in there and draw a line.

It was apparent in Carl's thread on the 661. He did just that.

It was on "Fin's Twins" IIRC