Ported Husqvarna 372xpw

[Chainsaw Jim]

I don't understand what you mean here.
How do you figure that the 372 is open port? And if that were so, how is it you've added "closed port-ness" to it?

Whether the lowers bottom or side feed has nothing to do with being open or closed, if that's where this is coming from...

Here's a closed port cylinder...

And here's open port cylinder....

I obviously didn't close the port. I don't know how you got that out of what I said. The piston is a closed port style piston after modifying it, giving it the closed port function.

 

[Chainsaw Jim]

definitely runs better then i thought it would although no better then a stock saw with that length bar i figure. i bet if you ran a shorter bar it would really shine.

Well I'm getting ready to put a brand new oem piston in another xpw so I can physically compare it with this one. I'll make cuts on the same test log. I've ran both 372xp and xpw in the stock form and I don't think they can touch this.

 

[Big_Wood]

both those cylinders are closed port

 

[bwalker]

Here's a closed port cylinder...View attachment 440118

And here's open port cylinder....View attachment 440119

I obviously didn't close the port. I don't know how you got that out of what I said. The piston is a closed port style piston after modifying it, giving it the closed port function.

Open port cylinders have transfers such that they don't have a cylinder side wall.
Both of the pics you posted are of closed port cylinders. They just have different designs as it pertains to where the meet the crankcase.

 

[wcorey]

So what do you call the type of transfer ports that have no horizontal bridge on the cylinder wall that creates upper and lower openings?
To me that is open port and has always been the differentiation between open and closed...

While certain types of pistons are typically associated with certain types of transfers, the piston isn't what defines open or closed port. (IMO)

 

[mdavlee]

Just bottom fed transfers and through the piston fed transfers.

 

[Onan18]

An open port has no divider between the top and the bottom, a Stihl 029/039 or a Husqvarna 257 are good examples of open port.

Joe

 

[sunfish]

The quad port design on the 372 is already a superior design and needs very little work for gains. Seems like you undid some of the good there???

 

[Chainsaw Jim]

Seems like you undid some of the good there???

I guess, if you want to consider theoretical ideas and use them as fact. That seems to be the norm around here.

 

[sunfish]

I guess, if you want to consider theoretical ideas and use them as fact. That seems to be the norm around here.

Nothing wrong with experimenting, but so much has already been done with the 372 and documented here.

 

[bwalker]

I guess, if you want to consider theoretical ideas and use them as fact. That seems to be the norm around here.

As opposed to ideas with theory behind them?

 

[bwalker]

The quad port design on the 372 is already a superior design and needs very little work for gains. Seems like you undid some of the good there???

Yep.

 

[Chainsaw Jim]

As opposed to ideas with theory behind them?

An idea with theory behind it? Wouldn't that be a thought about a thought?

It's weird to me when I see someone react to my port job by saying "you ruined your saw" when I highly suspect they've never tried it to know either way.
I don't take offence to it.

 

[bwalker]

An idea with theory behind it? Wouldn't that be a thought about a thought?

It's weird to me when I see someone react to my port job by saying "you ruined your saw" when I highly suspect they've never tried it to know either way.
I don't take offence to it.

The 372 cylinder is a well known piece. Why reinvent the wheel?
And all porting schemes should have sound theory behind them.

 

[Chainsaw Jim]

The 372 cylinder is a well known piece. Why reinvent the wheel?
And all porting schemes should have sound theory behind them.

You should see what the original designer of that cylinder does to them. Maybe he intentionally left room for improvement so he can continue his business hopping up these saws. I don't know, I'm not the expert on these cylinders. But one thing I will tell you is the overlap from the cylinder to the case is incredible, and correcting that is a huge gain alone. And I do have a sound theory on this. My theory was to eliminate the dead space causing turbulence between the piston and cylinder, and to allow flow through the piston as well. The piston will run cooler.


I used to be a union sheet metal worker and that involves air flow over great distances. One of the most important parts of the job was to eliminate any turbulence or dead space which interfere with air flow.

 

[bwalker]

Bulk flow is not the issue in a two stroke. Timing is everything.

 

[Chainsaw Jim]

Bulk flow is not the issue in a two stroke. Timing is everything.

No, a faster unrestricted flow vs. a lesser flow from restrictions is the issue.

 

[sunfish]

But one thing I will tell you is the overlap from the cylinder to the case is incredible, and correcting that is a huge gain alone.

Yes, matching the lower transfers to the case is huge on all the quad port Huskys and should be done. But opening up the lowers excessively is, or can be going backwards.

 

[Chainsaw Jim]

Yes, matching the lower transfers to the case is huge on all the quad port Huskys and should be done. But opening up the lowers excessively is, or can be going backwards.

I'd be very interested to hear info on any experience you have with opening up lowers excessively. I can't find anything with any pics or other information other than the "guess this piston" thread Snelling started a while ago. He had good results with that saw. I don't know how long it held up, but I'm assuming it still cuts.
My next thought is to see if crankcase stuffer cups from the 576 will fit it.

 

[bwalker]

I'd be very interested to hear info on any experience you have with opening up lowers excessively. I can't find anything with any pics or other information other than the "guess this piston" thread Snelling started a while ago. He had good results with that saw. I don't know how long it held up, but I'm assuming it still cuts.
My next thought is to see if crankcase stuffer cups from the 576 will fit it.

Reducing case volume will boost hp slightly, but will also narrow the power band and increase fuel consumption.