Chainsaw Porting Theory

[jmssaws]

My brother went to school for that kind of stuff. He used to be a fanatic about it. He would first find the resonate freq. of the car and then tune the box to the exact freq. it made for one bad ass stereo let me tell ya. I'm just not sure how he would apply that to chainsaws

I'd love to have a bad ass stereo system on my saw!

 

[jmssaws]

Every time I added a pipe my 66 gained. I have one goin out the front but it isn't straight out. It hits the wall of the pipe and exits out both sides.

View attachment 13936

Bigger the better.
What i ment is a 1 1\2" opening on one side will out perform a 3/4" opening on both sides. On a 066,I've not tested any other saw.

My 66 and 460 have the same muffler and you can put the screen in my 066 and there's no change but it will hurt the 460.

 

[Deets066]

How long have you been using the front cover set up?

Probly 30 tanks

 

[paragonbuilder]

Bigger the better.
What i ment is a 1 1\2" opening on one side will out perform a 3/4" opening on both sides. On a 066,I've not tested any other saw.

My 66 and 460 have the same muffler and you can put the screen in my 066 and there's no change but it will hurt the 460.

A 1.5" hole is 1.767 sq in
A 3/4" hole is .442 sq in
So 2 3/4" holes aren't even close to an 1-1/2" hole
It would take four to be approximately the same


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[jmssaws]

A 1.5" hole is 1.767 sq in
A 3/4" hole is .442 sq in
So 2 3/4" holes aren't even close to an 1-1/2" hole
It would take four to be approximately the same


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That's why I use one big port,I also don't like how dual ports sound but lots do.

 

[smokey7]

I am also a fan of one hole with a deflector on the side. Usually 3/4-1" square ish.

 

[Deets066]

That's why I use one big port,I also don't like how dual ports sound but lots do.

I don't like the sound of the dual port covers either.

Here's dual pipes, one is 1" and the the other is 1-1/4"

 

[countryhog]

Taking my pp375 down and thinking bout widening the exhaust port some. Not gonna screw with the vertical. So what is the max recommended width I can make the port as relates to the cylinder? Also since the cylinder is chrome what special issues should I be careful of

 

[Al Smith]

They say about 60 percent measured straight across so as not to snag a ring .Be sure to put a little chamfer on the inside ,craytex is good enough .Doesn't take much but it should have some .

 

[drf256]

Anyone wanna talk TRANSFERS again?

We did a thread on it already, but more discussion on it would be interesting. Especially now that we have hashed out 38 pages about the other portions of a build.

Transfers would certainly be considered the black magic of chainsaw porting theory and technique.

When they open, where they open, how they open, etc....

You can have a saw from 2 different builders with the same numbers that run completely differently.

Then there's quads, duals, bridges, fingers, boost ports, etc....

I'm interested in any opinions you guys have.

 

[drf256]

I'm particularly interested in the upper entry pockets.

The higher one takes a transfer over stock, the more the entry angle is going to change over what the factory gave us.

There's an old diagram, I'm sure Jeremy @Adirondackstihl has it, that shows 90* vs. angled entry transfers. IIRC, the closer to 90* you get, the peakier but more powerful you get.

The factory quad setups seem to favor a 90* entry in the mains/exhaust side port that opens before the secondaries. So they angle the transfer tunnel towards the intake, but they open it squarely across the piston crown on the exhaust side first.

So has anyone experimented with different pocket entry angles?

 

[wigglesworth]

I think actual opening point is way more critical than shape/entry angle....

 

[drf256]

I think actual opening point is way more critical than shape/entry angle....

How do you like to open dual ports?

The more I'm learning, the more confused I'm becoming.

Do you open square, intake first, exhaust first, etc?

 

[paragonbuilder]

I think actual opening point is way more critical than shape/entry angle....

So is entry angle one of those small details that take a saw from good to great, like thinning carb shafts, etc?


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[XP_Slinger]

So is entry angle one of those small details that take a saw from good to great, like thinning carb shafts, etc?


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I think that is the case. How the transfers "aim" the fresh charge directly effects how fast and efficiently the exhaust is pushed out of the cylinder.

 

[drf256]

So is entry angle one of those small details that take a saw from good to great, like thinning carb shafts, etc?


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I think it plays a big role actually.

Also likely the reason that some models do better with popup Pistons.

 

[paragonbuilder]

I can see a 90° entry angle as increasing velocity and spraying the charge into the cylinder, as the charge slams into the top before entering the cylinder, whereas a tapered entry angle would seem to just redirect the stream.



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[paragonbuilder]

Which one creates what kind of power I have no idea...


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[Mastermind]

So is entry angle one of those small details that take a saw from good to great, like thinning carb shafts, etc?


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Exactly.

I think it plays a big role actually.

Also likely the reason that some models do better with popup Pistons.

I've seen some horrible looking gouged out transfer ports in engines that run like hell. No thought at all but into the angles.....and the heights all over the place.

Sometimes I wonder why I try so hard......

 

[lwhaples]

I'm still trying to figure which cutter to use. They seem to dance around. But it sounds like I should go back in and get closer to the 90