Popup vs Flat Top?

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Mastermind

Work Saw Specialist
Joined
Nov 21, 2009
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MS361 with popup.jpg


The popup VS flat top thing is still in the air........so I wondered if this could possibly help.....

The green line is a ported MS361 with a popup (I did not port it).

It makes MAX power of 5.028 HP at 10,000 RPM

Here is aMS261 I did with a flat top.

Masterminds261cmvsstock261cm_zps7aecf5ff.jpg
At 10,000 RPM this 50cc saw makes almost as much power as the 60cc saw with a popup at the same RPM......and even more power at every point afterward.

Not trying to cause trouble........I just really believe that flat top pistons will make more power than popups, and think this goes a long ways toward proving it.
 
Less disruptive flow from the upper transfer ports across the piston crown.
Others argue that turbulence is good. I have a very hard time believing that a .035" bump is going to have a significant affect on real world performance.

I commented earlier today on the only way to put this to rest. I'll go find that post.
 
Here it is.

The only way to really test this popup vs cut squishband thing is to take a strong saw with a popup and run it on the dyno. Then replace the piston in that saw with a flattop, cut the squishband to result in the same compression, re-port to the same timing numbers, and re-dyno it. Anything less, and you're testing variables other than popup vs cut squishband. I've built 346s both ways and my popup saw was faster...measurably so.
 
blsnelling said:
The only way to really test this popup vs cut squishband thing is to take a strong saw with a popup and run it on the dyno. Then replace the piston in that saw with a flattop, cut the squishband to result in the same compression, re-port to the same timing numbers, and re-dyno it. Anything less, and you're testing variables other than popup vs cut squishband. I've built 346s both ways and my popup saw was faster...measurably so.


I would agree with this except for one more point. The squish gap would also have to be the same in both.
 
Go get Brush Ape/Harley T or who ever he is this week.

Randy gets lots of giggle from him too !!!!

it's to late man. old-cats already here. this is just gonna get all serious and such. wait til mudstain mike shows up. all the fun will be sucked right out of this. may as well lock it now :nofunny:
 
i'm not on anyones side. i'm here to back up the opposite of whoever already has the most back up. if i remember the last thread right i'm gonna have to default heavily to backing up brad here today. it's gonna suck cause wiggz really puts on some heavy fire.
 
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