Flat top or pop-up

[woodyman]

Which would make better power in a ported 346xp a pop-up or a flat top piston with 200 psi?

 

[blsnelling]

It would take a dyno to notice the difference.

 

[Tree Sling'r]

Flat- Pop.

 

[Dennis Cahoon]

Show me a modern bike engine with a pop-up piston!

 

[blsnelling]

Show me the dyno results of a chainsaw with both, everything else being equal.

 

[Dennis Cahoon]

Show me the dyno results of a chainsaw with both, everything else being equal.

Quit arguing Brad!......people in the "know" don't use pop-up pistons.....Period!

 

[FATGUY]

who do you know that's in the "know"?:tongue2:

 

[dl5205]

If compression and timing were the same, would dished be better still?

 

[McCulloch1-52]

Which would make better power in a ported 346xp a pop-up or a flat top piston with 200 psi?

All a pop-up piston really does helps gas from not escaping through the exhaust port during intake stroke.

 

[bucknfeller]

If compression and timing were the same, would dished be better still?

Maybe in theory because of the added displacement. But in reality you could never get the compression as high in the same jug.

 

[blsnelling]

I'm sure a .035"-.040" bump in the center of the piston, with a 45° shoulder, really blocks a lot of exhaust.

 

[Simonizer]

Maybe in theory because of the added displacement. But in reality you could never get the compression as high in the same jug.

?????????? Added displacement?

 

[komatsuvarna]

I'm sure a .035"-.040" bump in the center of the piston, with a 45° shoulder, really blocks a lot of exhaust.

LOL yeah I cant see that holding back much.


I still like a popup on some saws. On some, if you cut the chamber and base a lot it takes a lot of grinding to get the uppers back up where they need to be....often I can't get them flat enough on top to suit me and just have to deal with an bit of an upward angled transfer. A popup piston helps a little with this issue because the piston crown is dropping along with the cylinder.

Never done a 346 so I can't really comment on them. I should do mine one day.....

I'd still rather have a flat top piston 99% of the time....

 

[mweba]

?????????? Added displacement?

I melt the piston crown on all my saws making them drooop. Bam, no replacement for displacement.



I'd think a man with your training would know such things :msp_wink:

 

[Simonizer]

That's like cutting a foot off the bottom of a blanket and sewing back on to the top to make a longer blanket lol.

 

[dl5205]

Maybe in theory because of the added displacement. But in reality you could never get the compression as high in the same jug.

You don't think anyone could get 200 psi out of a 346 with a dish?

I'm just asking, I've never tried.

 

[Boleclimber]

Does anyone have a husky 350 that can be squish cut, run a oem piston and touch 200 psi? Or put a 350 piston in a 346 with the same intent. I bet hardly any of the combustion chamber would be left and possible issues with rings riding past the Nikisil coating.

 

[J.Walker]

Which would make better power in a ported 346xp a pop-up or a flat top piston with 200 psi?

You need one of each to experience the pleasure!

I like the flat top for cutting firewood and the pop-up for doing limbing.
If I were going to have another 346 done-up it would be a flat top.

 

[blsnelling]

I like the flat top for cutting firewood and the pop-up for doing limbing.
If I were going to have another 346 done-up it would be a flat top.

Hello Jack. Can you please explain?

 

[Jacob J.]

Flat- Pop.

They drink a lot of flat-pop in Mexico. I bought a Coke in a general store on the Baja peninsula once, it was flatter than a roadkill Crow.