Open port/ closed port?

[Trigger Man]

Sorry for asking newbie questions, but I get confused with terminology most of the time.

When talking about saws and there engines what does closed port and open port mean? Also do these different designs use different pistons or does this describe what the piston is ?

 

[pioneerguy600]

Sorry for asking newbie questions, but I get confused with terminology most of the time.

When talking about saws and there engines what does closed port and open port mean? Also do these different designs use different pistons or does this describe what the piston is ?

Open port cylinder is a cylinder with the ports open from the cylinder base up to the point of transfer from the port to the top of the piston. Closed port is a cylinder with the ports closed for a portion of their height from the base up to the transfer point. An open window piston will work with either design but a non windowed piston will only work with a open port cylinder.
Pioneerguy600

 

[Jacob J.]

In some saws you'll lose a little spool-up time when you put a windowed piston in an open-port cylinder. Most of the time though it works just fine.

 

[Trigger Man]

Thanks fella's sending rep.

 

[Trigger Man]

In some saws you'll lose a little spool-up time when you put a windowed piston in an open-port cylinder. Most of the time though it works just fine.

Jacob what do you mean buy spool up time?

 

[wigglesworth]

Jacob what do you mean buy spool up time?

He means the amount of time from idle to full RPM's.

 

[AKDriveSprocket]

Is the RPM of the saw lower on a closed port?

 

[Jacob J.]

Is the RPM of the saw lower on a closed port?

Not typically. In most modern saws, the top no-load speed is about the same in open and closed port saws.

 

[Trigger Man]

Is open port better or is closed port better or are they about the same?

 

[nanuk]

windowed piston?

windowed piston has the skirt all the way around?

 

[Jacob J.]

Is open port better or is closed port better or are they about the same?

Typically the closed-port engine is going to have more torque.

windowed piston has the skirt all the way around?

No, that's a full-circle or full-skirt piston.

 

[Jacob J.]

Open port cylinder (left, Husky 36) vs. closed port cylinder (right, Husky 272):

Windowed piston (left, Jonsered 670) vs. Non-windowed piston (right, Husky 257):

 

[AKDriveSprocket]

Which jug did the bug like best?

 

[nanuk]

Thanks For That!

Open port cylinder (left, Husky 36) vs. closed port cylinder (right, Husky 272):

Windowed piston (left, Jonsered 670) vs. Non-windowed piston (right, Husky 257):

JJ!

 

[nanuk]

sorry to drag up an old thread....

Open port cylinder is a cylinder with the ports open from the cylinder base up to the point of transfer from the port to the top of the piston. Closed port is a cylinder with the ports closed for a portion of their height from the base up to the transfer point. An open window piston will work with either design but a non windowed piston will only work with a open port cylinder.
Pioneerguy600

but... was doing some research..
a 372 has a closed window piston but is an closed port cylinder...

what am I missing?

 

[nanuk]

perhaps I found my answer

the ports on the 372 originate from outside the cylinder wall, on others they are originating inside the wall, but lower down.

a la an 066 that Evan posted pics of.

 

[Husqvarna87]

would this piston and cylinder be open or closed port?

View attachment 270295

 

[mt.stalker]

would this piston and cylinder be open or closed port?

View attachment 270295

open