Let's Talk Transfers

[jmssaws]

it happens a lot slower then you think

Me shooting my wad?

 

[Canadian farm boy]

What would be a good indication of a saw that has low transfer velocity? Bog off idle? Slow throttle response?

 

[tree monkey]

I think 10 is optimistic.

Velocity is direction that's why u lose when velocity is lost.

how fast do you think the charge is moving with less then 10 psi behind it?

if your port timing is to short, you increase velocity and loose volume.
if your port timing is to long , you loose velocity and volume. because of back stuffing the port.
it's all about volume, timing, and direction.
f you make a port to wide you loose direction.

 

[jacob j.]

What would be a good indication of a saw that has low transfer velocity? Bog off idle? Slow throttle response?

The ones I've seen will have good acceleration and will four-stroke while not under a load to a high RPM range, but fall on their face in the cut. Walker's saws from the early 2000's were that way. They would hog out the transfers and gut the muffler and the saws had no torque band at all.

If you look at the Sachs-Dolmar designs from the 70's and 80's- they had long, narrow transfers with a small upper. Those saws consistently had a fat torque band and would hold decent RPM in the cut with a long bar.

 

[jmssaws]

how fast do you think the charge is moving with less then 10 psi behind it?

if your port timing is to short, you increase velocity and loose volume.
if your port timing is to long , you loose velocity and volume. because of back stuffing the port.
it's all about volume, timing, and direction.
f you make a port to wide you loose direction.

They will be closed before they shoot there entire wad.

 

[jmssaws]

That's why I say you want all you can get when they open, which is more,velocity or volume?
Is a small amount in the right direction better?

 

[awol]

I think 10 is optimistic.

Velocity is direction that's why u lose when velocity is lost.

Ahhh yes, but always remember that volume equals velocity; that is if you are careful to make sure that the port opening into the cylinder is the smallest point of the entire transfer tunnel. Getting more flow by widening the lowers will increase velocity through the uppers, if left unwidened.

 

[Miller Mod Saws]

On many of your quad ports one port is angle upward yhe other is flat. It's crossed my mind to try and mimic this in a dual port. Mark the port and half of it grind flat the other half at an angle but opening at the same time. Has anyone tried this?

 

[paragonbuilder]

On many of your quad ports one port is angle upward yhe other is flat. It's crossed my mind to try and mimic this in a dual port. Mark the port and half of it grind flat the other half at an angle but opening at the same time. Has anyone tried this?

I think that is what Al was trying to accomplish in the 262 he's working on. Here was his post.

I'm attempting a pseudo-Quad port on this saw.

I spent a bunch of time grinding the inside of the uppers. The entry angle is flat on the exhaust side and slightly ramps up as it approaches the intake side.

Unlike many saws (like the 026), this 262 has a nice fat fin on op of the exhaust part of the external upper tunnel. So you can grind away without fear of going through.

Most quad timings I've seen open the area over the exhaust part of the piston first. Also it's at a flatter angle of entry than the mains. I opened an exhaust lip 1* sooner to blow off the exhaust side of the piston crown first.

So the jug is now set at 103 ex, 117 upper exhaust lip, 118 mains and fingers at 115.

Flow inertia and direction should make the ex lip flow very little.

In my minds eye, I see a wider band of flow emanating from the uppers but with the same direction.

I aimed for "feathering" out the intake charge all around the intake side of the cylinder.

It may be a total dud, if so, it will go in the tub of shame. At least I got a few hours on mental therapy from the grinding.

If it work great, we all learned something.

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[Miller Mod Saws]

I think that is what Al was trying to accomplish in the 262 he's working on. Here was his post


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Op thank you. I missed that post! Lol.

 

[paragonbuilder]

Op thank you. I missed that post! Lol.

Carl, That post is from his saving a 262 jug thread. Sorry if I confused you.


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[drf256]

I think that if you think of flow as one cycle at a time, you get the theory of how it works, but not what's actually happening.

I feel that at 15,000 rpm, there's a plume on transfer charge coming out. How you shape that plume determines optimum power.

The question is what shape is the best and how do we shape it like that.

 

[XP_Slinger]

Good thread. What can be gained by opening up the lower transfers in conjunction with grinding on the uppers. Seems to me that if you were to improve flow down low it would translate to better velocity as the transfer opens because of the reduced area of the port up top. Same as a carb venturi, big to small equals velocity. Newbie to porting theory here, be nice please

 

[jmssaws]

I think that if you think of flow as one cycle at a time, you get the theory of how it works, but not what's actually happening.

I feel that at 15,000 rpm, there's a plume on transfer charge coming out. How you shape that plume determines optimum power.

The question is what shape is the best and how do we shape it like that.

It's cumulative no doubt.
Your spot on,you have to think about it like a water hose.

 

[tree monkey]

it's not water, air doesn't flow the same

 

[jmssaws]

it's not water, air doesn't flow the same

I'm well aware of that.
Think of it as a air hose then, it only stops flowing for a millisecond

 

[jmssaws]

Your right Scott I'm just explaining how I see it.
You build a strong saw so do i, I seriously doubt there night and day inside.
I don't think there's a black and white answer.

 

[paragonbuilder]

Good thread. What can be gained by opening up the lower transfers in conjunction with grinding on the uppers. Seems to me that if you were to improve flow down low it would translate to better velocity as the transfer opens because of the reduced area of the port up top. Same as a carb venturi, big to small equals velocity. Newbie to porting theory here, be nice please

As you can see from reading through the thread, there are many ways to gain power from a saw. You may very well improve the saw. But there is also the theory of keeping as much material in the case to increase case compression. We're all learning here!


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[tree monkey]

I don't worry about case volume anymore. unless I want to change it a lot.

 

[paragonbuilder]

I don't worry about case volume anymore. unless I want to change it a lot.

So if you see grinding in the lowers or case matching as enhancing flow, that is more important to you?


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