Chainsaw Porting Theory

[Keith Gandy]

Wtf... Deets can't even spell Stihl right.

 

[Keith Gandy]

Could the Venturi effect be how it overcomes exhaust pressure initially?

I think so. When the charge starts in it is probably acting sorta like a venturi effect and taking a deep breath and creates negative pressure/vaccum at the intake port exit or negative pressure in the combustion chamber . Too much back pressure would damper that venturi effect? After theres a reduction in back pressure and a negative pressure then the full blunt of the case compression will be enough to transfer the charge and blow the exhaust on out? Im seeing getting the exhaust/blowdown and intake out of wack with each other pretty easily? Just a few ideas I have been pondering

 

[Brewz]

I usually take off the casting dags and burs around he base and windows.
I doubt it makes any noticeable difference but it makes me feel better knowing they are gone

 

[mdavlee]

Wtf... Deets can't even spell Stihl right.

Nah. The good German saw is finally getting known

 

[jmssaws]

Wtf is a dolmar? Is it a bread making machine? Feminine deodorant?

 

[huskihl]

Wtf is a dolmar? Is it a bread making machine? Feminine deodorant?

Easy there, big fella. Mike Lee's gonna go all Appalachian American on yer ass

 

[jmssaws]

I should see mike in a few days so he can kick my sack then.

 

[jmssaws]

I've not givin up on it yet but so far this one is a stinker.

 

[Deets066]

Some epoxy might bring it back J, those are some huge fingers

 

[jmssaws]

Some epoxy might bring it back J, those are some huge fingers

The lowers are filled and my 66 runs great and has bigger fingers than it.

It ran terrible before fingers, the transfers are to high,I'm going to try some more intake,it's 80

Fingers are at 113 mains 115

 

[merc_man]

The lowers are filled and my 66 runs great and has bigger fingers than it.

It ran terrible before fingers, the transfers are to high,I'm going to try some more intake,it's 80

Fingers are at 113 mains 115

what do those fingers do ya cut in.
New to porting Just trying to learn. never seen that before.

 

[jmssaws]

what do those fingers do ya cut in.
New to porting Just trying to learn. never seen that before.

Direction mainly but I suppose it will help filling the cylinder with fresh charge.

I've had them work and I've had them do nothing,I probably won't use them anymore.

The last couple I've done had no fingers or bridges and ran great.

I think if they work then your transfers are off a little.

 

[Deets066]

what do those fingers do ya cut in.
New to porting Just trying to learn. never seen that before.

They just look cool

 

[Keith Gandy]

Direction mainly but I suppose it will help filling the cylinder with fresh charge.

I've had them work and I've had them do nothing,I probably won't use them anymore.

The last couple I've done had no fingers or bridges and ran great.

I think if they work then your transfers are off a little.

I would think a progressive transfer would achieve the same as a finger?

 

[Keith Gandy]

2° on the intake side of the transfer?

 

[Deets066]

High mains will kill a saw

 

[Keith Gandy]

Or a bridge should achieve basically what a finger is?

 

[Deets066]

I would think a progressive transfer would achieve the same as a finger?

Or a bridge should achieve basically what a finger is?

So.... What if you had bridges, fingers, and sloped uppers?

 

[Keith Gandy]

So.... What if you had bridges, fingers, and sloped uppers?

Id probably say lost velocity and very quick to progress backwacks instead of gaining. Ive been thinking lately on 25% of the transfer on the intake side adjusted to desired port # and leave the other close to factory?

 

[Keith Gandy]

U may would have an initial purge to that one side with increased velocity then the rest of the transfer opening and pushing charge on in?