Upper transfer angles

[mdavlee]

I don't leave any lips anywhere. I try to get them flat or tapered if that's the desired outcome. I tapered the intake side on the 7910 about 2°. The exhaust side is flat. Hopefully this afternoon I'll try it. The muffler isn't welded back together but it's only one side that the lip broke off. I'll see if it's tight enough to seal when it's tightened up.

 

[Keith Gandy]

Thats usually what I do too Mike. Flat toward ex. And tapered on intake side

 

[Stihlbro]

Good discussion going. Quad port motors seem to make better performers. So on a two port motor why not try altering like a 7900 is? Or 346,357,365,372.

Here is what I tried.


Not a finished cylinder, but you get the concept.

 

[Keith Gandy]

Good discussion going. Quad port motors seem to make better performers. So on a two port motor why not try altering like a 7900 is? Or 346,357,365,372.

Here is what I tried.
View attachment 696

Not a finished cylinder, but you get the concept.

Bridge angled toward intake and port timing is progressive with 1 side flat and the other angled? Nice! Quad concept in a 2 port?

 

[drf256]

Good discussion going. Quad port motors seem to make better performers. So on a two port motor why not try altering like a 7900 is? Or 346,357,365,372.

Here is what I tried.
View attachment 696

Not a finished cylinder, but you get the concept.

Do you find that aiming the bridge port at a different spot makes any difference?

I usually aim for the area that the Squishband meets the cylinder wall. Yours look like they are aimed at the wall just above the intake.

 

[Redfin]

Did you fill that to make a quad? Its hard to see from the pics?

 

[Stihlbro]

It is filled with epoxy. Rings would never touch. The concept was for the aiming of the incoming charge. It's a work in progress. Lol! On of those laying in bed ideas that I could reinvent the wheel.

 

[jmssaws]

I've stopped widening them completely and just raise,I think a 66 likes velocity over flow plus I use fingers in most so I see no point in widening. I do remove the lips and keep timing the same from corner to corner.
I've noticed with a cylinder that had poor numbers that I have to raise the transfers farther wich makes the opening bigger they loose power so I keep them small as i can. But that's how I do one particular saw. By know means is that the only way to breed this goat.

 

[Redfin]

Well it looks like a dang fine idea Stihlbro.

 

[Mastermind]

I've heard of someone else dividing the transfers on a Stihl.maybe they will chime in. I'm not gonna out em.

 

[drf256]

I thought that the division for quads was to allow a bigger cross sectional area of intake and still keep ring support by the central bridge of plating between them?

I can see higher velocity occurring though.

I'd be interested in knowing if that epoxy bridge does anything.

 

[Keith Gandy]

I thought that the division for quads was to allow a bigger cross sectional area of intake and still keep ring support by the central bridge of plating between them?

I can see higher velocity occurring though.

I'd be interested in knowing if that epoxy bridge does anything.

Look in a Husqvarna quad. Both primary and secondary have totally different shapes and angles

 

[drf256]

But charge velocity is associated more with torque at lower rpm, not horsepower per se.

Flow in multiple small passages should still be less than in one large port because of laminar flow resistance (poiseuille's law).

 

[drf256]

Look in a Husqvarna quad. Both primary and secondary have totally different shapes and angles

Ahhh,

I see where he's going with that now. My thought were to carve different angles without the divider in the same port.

 

[Keith Gandy]

On a quad I see one aimed toward cc and intake wall for that swirling effect and the other angled toward center of cc? Run water through the transfers and its easier to see what they r wanting to accomplish

 

[drf256]

I see little ring support in the exanple above. Cool stuff and outside the box thinking for sure. I just wonder.

 

[Keith Gandy]

I see little ring support in the exanple above. Cool stuff and outside the box thinking for sure. I just wonder.

But it was a 2 port to start with no support in the middle ? He only widened the bridge toward intake alil. It has the same support as before he added the partition.

 

[drf256]

It looks like he extended the transfer over towards the intake as well. I could be wrong.

 

[jmssaws]

I don't worry about hanging one in a transfer, a wide exhaust is were you will get a ring. U could get a ring end in a transfer by widening to much, that's why I like a husky piston in some stihls, great pin location.

 

[Keith Gandy]

It looks like he extended the transfer over towards the intake as well. I could be wrong.

He did but not alot. Look at it in relation to the bottom transfer width