Chainsaw Porting Theory

[MustangMike]

Yes, but that is another subject. I'm sure the case volume on a 660 is quite different also.

 

[jmssaws]

It's about balance....

And I've still got so much to learn.

I call it harmony, it's not just a set of numbers,it's a combination of everything working together and it's easily felt and heard.

I'm not sure in what order things need to be in or the proper terminology the call it but you know it when you find it, a saw that runs truly free is a beautiful thing.

I sometimes change things many times on a saw before I find it and I've never found it on some.

 

[jmssaws]

How many of you guys have had a great running saw but thought it was missing something and took it apart and changed one tiny little thing, maybe the entry of the transfers on the exhaust side just a fuzz and put it together and it was like a weight was lifted off of it,then think you learned something only to never be able to reproduce it the same again.

It's not a excact science.

 

[riverrat2]

It's about balance....

And I've still got so much to learn.

So happy here!!!! This place is the Schiznit!!!!! was so burn't out on the other place,,,, Now I'm enjoying posting again and putting a few of my old project saws together....
And I don't have to ignore button the plastic people!!!!!

 

[Deets066]

How many of you guys have had a great running saw but thought it was missing something and took it apart and changed one tiny little thing, maybe the entry of the transfers on the exhaust side just a fuzz and put it together and it was like a weight was lifted off of it,then think you learned something only to never be able to reproduce it the same again.

It's not a excact science.

I did just the opposite, took a great running saw and made it run like chit.

 

[Deets066]

How many of you guys have had a great running saw but thought it was missing something and took it apart and changed one tiny little thing, maybe the entry of the transfers on the exhaust side just a fuzz and put it together and it was like a weight was lifted off of it,then think you learned something only to never be able to reproduce it the same again.

It's not a excact science.

I did just the opposite, took a great running saw and made it run like chit.

 

[PA Dan]

Wow you did it twice!

 

[Deets066]

Wow you did it twice!

Just gettin it out of the way for the next one

 

[PA Dan]

Just gettin it out of the way for the next one

Right on! You learned what not to do!

 

[jmssaws]

I did just the opposite, took a great running saw and made it run like chit.

I also have fixed one till it was broke.

 

[huskihl]

Just gettin it out of the way for the next one

Studies show that if you study drunk, you'll do better taking the test drunk....

Study sober, take the test drunk?

 

[drf256]

It's about balance....

And I've still got so much to learn.

The minute you think you know it all, it's over for you. An open mind and free discussion is where it's at.

Anyone familiar with the Citibank building in NYC? The one with the 45* square roof?

The brightest and best architects designed it. They completed the project and stood gleaming at their accomplishment.

An 18 yo architecture student called the head architect and told him "your building is gonna fall down sir". They actually pulled this kid in and listened to his theory. They opened every wall, where needed, and added bolts to the welded beams where needed. The student was right.

So anyone can come up with a better idea because we all see things differently.

So let's carry on this discussion freely

 

[drf256]

Ok. INTAKE, I'll throw this dirty (actually clean) word out there.

So we have this port, which in our cases, opens and closes by the piston skirt. There may still be modern chainsaw designs with rotary or reed valves. Please forgive my ignorance on that matter.

 

[drf256]

We have a roof, that the ring(s) sometimes descend into. Other times not.

We have the floor, the most critical part of the port, as it controls opening, closing, and thus case compression.

We has assymetric designs of both by the OEM. Some roofs have a finger like plate extension for the rings (028S/034 are examples).

Some floors are assymetric, like on the stihl 036 and others. This shape can vary duration a bit because of mix viscosity. At higher rpm, you should get less dynamic intake duration and possibly better case compression. I've personally found the Stihl 036, with an intake floor of 84 after porting, to be one of the most throttle responsive saws I've ever played with.

Is that from port shape, intake duration, the large intake port?

Feel free to discuss if you would like to. I know I'm listening.

 

[paragonbuilder]

I wish I had something to add. Seems like everyday I'm learning something on this site.


Sent from my iPhone using Tapatalk

 

[leadfarmer]

I wish I had something to add. Seems like everyday I'm learning something on this site.


Sent from my iPhone using Tapatalk

Hahaaa yep me to. I'm realizing I'm dumber than I originally thought [emoji36]

 

[Deets066]

We have a roof, that the ring(s) sometimes descend into. Other times not.

We have the floor, the most critical part of the port, as it controls opening, closing, and thus case compression.

We has assymetric designs of both by the OEM. Some roofs have a finger like plate extension for the rings (028S/034 are examples).

Some floors are assymetric, like on the stihl 036 and others. This shape can vary duration a bit because of mix viscosity. At higher rpm, you should get less dynamic intake duration and possibly better case compression. I've personally found the Stihl 036, with an intake floor of 84 after porting, to be one of the most throttle responsive saws I've ever played with.

Is that from port shape, intake duration, the large intake port?

Feel free to discuss if you would like to. I know I'm listening.

I would say less case compression plays a part of letting the saw run "freely"

I'm not sure as to why but a larger intake has more throttle response and rpm. Less intake is where the torque is at.

Once again, it's all about the balance and what each saw responds well to, or what the operator wants to do.

 

[drf256]

The more case pressure and the smaller the cross sectional area of the transfers, the lower they need to be set to create the best cylinder transfer, from what I've gleaned from my research.

 

[Mastermind]

The 036 runs great with the intake at 85 or so. I do think it's shape helps with that.....but, I've never taken the time to shorten it either. I wonder....

Here's one for y'all.

044/046 I did several years ago.

It came back to be fixed a few days ago. In the first build, I had trimmed the piston skirt to add intake duration, and it also was running a pop-up piston. There were two broken jug bolts in the base, and it was in need of a lot of parts....

We used one of the aftermarket cases that Dave sells, and while Jon was getting it ready, I was making a new piston for it. The owner loved the way this saw ran, so I was just copying the old piston, and getting it back in service. Jon already had the piston mounted before I realized that the skirt was trimmed......rather than take it back off, I just left it stock.

Tracy killed trees with it for a few days, and it started flooding. He brought it back for us to check out. He said in smaller stuff, or in soft wood, the old saw was faster...but he was in some pretty big chestnut oak.....and in big hard wood the new version was much stronger. He also reported a longer run time per tank. The only complaint he had ever had about the saw was that it was a thirsty bastard.

So, here we can see that it goes right back to giving a user what they want. Faster in small stuff, more intake duration seems to work, but in bigger wood, the shorter duration allows more torque....

 

[jmssaws]

Definate Daves 064 hybrid is faster than my old saw with a short bar,intake is 83.
Put a 28 or 36" on them and my old saw will pull away. Intake is 78.

Like randy said the customer wants a short bar saw so that's what he's getting.

Big intake duration hurts tourqe but gains rpm.