Unsaid info about high compression heads

jaguar

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The research compared a non-squish head with 3 others with squish of varying squish velocities and the result was basically the same power for all but the stresses on the crank bearings varied a lot.
I know from riding my 100cc street bike down here in hot South America that 2 strokes lose a considerable amount of power at high heat. The squish band concentrates the main combustion towards the center, away from the piston edges which reduces heat at the rings which reduces friction which helps with power. It could be that the researchers (see http://www.dragonfly75.com/moto/SquishVelocity.html) didn't test for long enough times to see how with a squish band there is less power loss as the engine gets up to max heat.
 


Street Ryderz

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Jag and I have argued this one. He goes back to a 1970s SAE paper from a chain saw engineer comparing 4 heads with different squish. It goes in conflict with 40 years of research since and I'd suggest it might have even been put up to throw competitors off the scent trail. Blair, Jennings, Bell, David Vizard and others have covered this quite thoroughly. I don't want to diminish Jag's contribution in the slightest, and I think it all depends on how you look at it. A head does not significantly add to the intake charge, just changes how we burn it and alters the pressure/time rate. Jag has added a lot to these conversations and should be listened to. My interpretation could be wrong.
I've found your findings to be quite accurate in this and many topics using real world testing and results,As you have said the torodial style head with squish produces more torque and mid power with less run out at the top and really helps prevent detonation, Compared to the hemi head with no squish on the exact same set up with the same C/R the hemi will rev higher but with much less bottom and lower mid range power,IMO these real world results on the actual engine we all use here not a DS 100 or KDX 250 or any of the other engines his research is based on is more useful to all those trying to upgrade their engine.We all or should know that no 2 engines are the same even when the same make and model there are slight variables.And the difference between his reference engines and ours are vast,That said Jag's contibutions to this community are much apreciated but are also very outdated since he has not ever used an up to date engine,head,pipe,timmings and yet is a self proclaimed expert and that kinda erks me as there are many contributors with better working knowledge and real world experience that would never make that claim.
 

jaguar

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prettiest sweetest knife in the back I ever got but I'm used to that on this forum which is why I rarely visit.
 

gary55

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My interpretation of the squish band is it allows a engine to make more power rather than creating it it's self. Outside of the swirl effect that I'll leave to brains smarter than mine it's purpose was intended and still used to run higher compression by shielding a small portion of the charge from initial combustion to keep things more chilled and reducing opportunity for detonation.
 

6blueoval9

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@jaguar Ive read and like your stuff but I have to agree with doing your experiments or tests on up to date offerings...How something worked on a 250 cc with a completely different design other than being considered a 2 stroke doesn't really apply to our fairly flawed 2 strokes being made today.

My God, now we have billet cases and Dio reeds and case reed motors and more pipe offerings, huge carbs and yada yada yada...Were advancing and that's a good thing...Jump on the bandwagon with us.
 

Stoneman

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sux when an interesting topic goes to s*%T

would be interesting to look at it from both sides, but only one seems to be explained....

From what i can read so far there is some credibility on whats being said about what we understand how a squish band works

hope it gets back on track so we can all learn :)
 

gary55

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sux when an interesting topic goes to s*%T

would be interesting to look at it from both sides, but only one seems to be explained....

From what i can read so far there is some credibility on whats being said about what we understand how a squish band works

hope it gets back on track so we can all learn :)
It's a long read but pretty much explains squish bands along with a bunch of other 2 stroke stuff. Very interesting.http://www.amrca.com/tech/tuners.pdf
 

Street Ryderz

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Oct 14, 2016
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sux when an interesting topic goes to s*%T

would be interesting to look at it from both sides, but only one seems to be explained....

From what i can read so far there is some credibility on whats being said about what we understand how a squish band works

hope it gets back on track so we can all learn :)
I cant agree with something that's not true,AS big of a contributor to this community as he is,He should be on here reading more and at least keep up with what's going on.Saying that squish is not what is making power rather the increased C/R really is a contradiction in that using a squish allows the higher compression to be used safely and there fore make more power and controlled burn.We are not all sheep and we have to question those who know to learn aswell as point out when those we learn from are wrong that's how the world advances we all learn from each other!
 
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