Flat top or pop-up

[thomas1]

Brad........Next time you push down on your saw, in the middle of a cut.......you'll be coming out of the turn.......Hahahahahaha!

Just don't push down. No load rpm's are where it's at.

 

[Mastermind]

Popup 200 PSI. Well broken in work saw. This is an Oak cant.

200psi?

Is that much compression really needed? :msp_wink:

 

[spacemule]

Thanks for sharing Dan. I have a new 2153 here that I cut the squish band in. It has just shy of 220 PSI. It's still on it's first tank of fuel, so not even close to broken in. My 346 has a popup piston with just shy of 200 PSI. I'm anxious to get some time on the 2153 to make a fair comparison. It's not a perfect test for the popup/flattop debate. In addition to the piston difference, there's a 20 PSI compression difference, with the one getting past what you say is ideal. We'll see. Other than that, the two saws are close to identical in build.

Don't forget in this discussion, we're using chainsaws that run at WOT almost exclusively. We're not concerned with bottom/mid-range torque needed to come out of a corner.

Flat top with cut squish band. 220 PSI. First time to see wood. Pine log.
[video=youtube_share;p1OeCYOGElQ]http://youtu.be/p1OeCYOGElQ[/video]

Why use punky wood (pine at that--everything looks fast in pine) for a demonstration/comparison?

 

[thomas1]

Why use punky wood (pine at that--everything looks fast in pine) for a demonstration/comparison?

Seems like you may already know the answer. :msp_wink:

 

[blsnelling]

Why use punky wood (pine at that--everything looks fast in pine) for a demonstration/comparison?

Beggars can't be choosers. It's the only wood I had available at the time.

 

[blsnelling]

200psi?

Is that much compression really needed? :msp_wink:

Probably not

 

[spacemule]

Beggars can't be choosers. It's the only wood I had available at the time.

Well, I suppose when you run out of pine you could set a block of balsa or foam up to use for demonstrations too?

 

[woodyman]

Why use punky wood (pine at that--everything looks fast in pine) for a demonstration/comparison?

Is that why they use pine when they race hotsaws?

 

[woodyman]

Probably not

Why not?I raced a 346 that had well over that and had my ass handed to me and the saw was in use for 2 years prior.

 

[lmbrman]

200psi?

Is that much compression really needed? :msp_wink:

Randy, you should know it has nothing to do with need :hmm3grin2orange:

 

[Mastermind]

Randy, you should know it has nothing to do with need :hmm3grin2orange:

It was a loaded question.......I'm gonna let it go though.

 

[Hddnis]

This may be a little more seat of the pants vs. technical...


I had an Echo 4600 that I put a pop-up in and ported. Throttle response was great and top end torque was good. It is a easy handling saw and so I put an 18" bar on it running 3/8 low profile and used it for taking the tops out of Doug fir and pine. It worked good, was running 195psi.

Saw was a garage sale find that I got for $50 as a not running saw. It had very light scoring on the exhaust side, but nothing to worry about at all. They thought it was not running because they didn't know how to release the chain brake.

Anyway, after a little while I ordered a new piston for it, mostly just because I liked the saw and wanted it in top shape (and stuff)

So, I put the new piston it in stock. Squish was a little tighter than I normally like, but I decided to not cut a pop-up and just try it. Compression was 190psi with the new piston. But I can say that throttle response seemed fine, maybe just a hair slower, low end grunt was way up. It ended up being an even better top saw because you often wait for the wind to be right and then you have to cut like mad to get the top to fall just right, and that means you need torque to keep pulling the chain while you push on the saw. (yeah, I said push on a 45cc saw!)

So, in that saw, with the porting I had done, a pop-up didn't help. It may not be the same story for all saws with all port jobs. With a lot of this it can be luck, voodoo, experience, copying the other guy, dumb luck and a bit of science thrown in to keep it interesting.



Mr. HE

 

[lmbrman]

It was a loaded question.......I'm gonna let it go though.

It's not gone, just under the surface barely, we all know who cant handle high pressure, i mean compression. Heck, monkey and ape understand

 

[sachsmo]

Yes Sir, a pop-up seems to be such a waste,

just sayin'

They do have their place though;

Sadder?




7-10 McCulloch I turned into an e85 burner.

 

[wigglesworth]

I've turned a few....



Welded a few...



But the only way to go is...

 

[Mastermind]

Are you drunk again Wiggs?

 

[wigglesworth]

Are you drunk again Wiggs?

Not sure. What is today?

 

[Mastermind]

Not sure. What is today?

Yesterday.

 

[blsnelling]

I like dished pistons myself.

 

[Mastermind]

I've been doing some heavy reading on engine tech......dished pistons are the next big thing Brad.