Rod Posted February 17, 2020 Share Posted February 17, 2020 What kind of HP gains would you expect from simply taking the squish from Around .075 to as tight as you could run without contact on an 800cc engine Quote Link to comment Share on other sites More sharing options...
f7ben Posted February 17, 2020 Share Posted February 17, 2020 3 minutes ago, ACE said: What kind of HP gains would you expect from simply taking the squish from Around .075 to as tight as you could run without contact on an 800cc engine diminishing past about 40 thou and dependent on a myriad of factors like port timing and dome shape Quote Link to comment Share on other sites More sharing options...
Rod Posted February 17, 2020 Author Share Posted February 17, 2020 1 minute ago, f7ben said: diminishing past about 40 thou and dependent on a myriad of factors like port timing and dome shape I’ll take all I can get Quote Link to comment Share on other sites More sharing options...
XCR1250 Posted February 17, 2020 Share Posted February 17, 2020 Thermal expansion could become an issue. 1 Quote Link to comment Share on other sites More sharing options...
Rod Posted February 17, 2020 Author Share Posted February 17, 2020 2 minutes ago, XCR1250 said: Thermal expansion could become an issue. Well yes That’s why you can’t go to zero Quote Link to comment Share on other sites More sharing options...
XCR1250 Posted February 17, 2020 Share Posted February 17, 2020 1 minute ago, ACE said: Well yes That’s why you can’t go to zero That and you don't want to trap the fuel in the squish causing it to ignite there, squish is there to speed up the mix into the combustion chamber, I suspect you already knew that. Quote Link to comment Share on other sites More sharing options...
Rod Posted February 17, 2020 Author Share Posted February 17, 2020 Just now, XCR1250 said: That and you don't want to trap the fuel in the squish causing it to ignite there, squish is there to speed up the mix into the combustion chamber, I suspect you already knew that. Yes but too loose of a squish doesn’t blow it into the combustion chamber very well either on car engines we call it the quench and we run it as tight as we can without contact because it actually reduces detonation and encourages a better mix Quote Link to comment Share on other sites More sharing options...
XCR1250 Posted February 17, 2020 Share Posted February 17, 2020 (edited) 10 hours ago, ACE said: Yes but too loose of a squish doesn’t blow it into the combustion chamber very well either on car engines we call it the quench and we run it as tight as we can without contact because it actually reduces detonation and encourages a better mix Too loose slows it down, years ago 2 strokes didn't have/use a squish band. I use solder or clay to determine what I want to get to then mill or Lathe cut more to get there. Edited February 17, 2020 by XCR1250 Quote Link to comment Share on other sites More sharing options...
FrankieJames7 Posted February 17, 2020 Share Posted February 17, 2020 14 hours ago, ACE said: Well yes That’s why you can’t go to zero another reason is because of rod stretch. dependent on rpm and strength of rod. and not rod johnson either 2 Quote Link to comment Share on other sites More sharing options...
Rod Posted February 17, 2020 Author Share Posted February 17, 2020 Nobody answered my question though Quote Link to comment Share on other sites More sharing options...
FrankieJames7 Posted February 17, 2020 Share Posted February 17, 2020 well buy a dyno dumbass. you think someone on fs is going to tell you exact hp and torque gains by narrowing the squish band? it will give you gains across the entire rpm range, but will give best gains by limiting detonation. so the best gains aren't measured in hp, but in how much pistons that went kablamo in an engine running full blast Quote Link to comment Share on other sites More sharing options...
XCR1250 Posted February 17, 2020 Share Posted February 17, 2020 1 hour ago, ACE said: Nobody answered my question though Wouldn't be much, perhaps not worth a burn down, and every engine will be different. Quote Link to comment Share on other sites More sharing options...
Rod Posted February 17, 2020 Author Share Posted February 17, 2020 Just now, XCR1250 said: Wouldn't be much, perhaps not worth a burn down, and every engine will be different. Like 5-8 hp? Quote Link to comment Share on other sites More sharing options...
XCR1250 Posted February 17, 2020 Share Posted February 17, 2020 3 minutes ago, ACE said: Like 5-8 hp? Unlikely that much. Quote Link to comment Share on other sites More sharing options...
f7ben Posted February 17, 2020 Share Posted February 17, 2020 3 minutes ago, ACE said: Like 5-8 hp? No Quote Link to comment Share on other sites More sharing options...
Rod Posted February 17, 2020 Author Share Posted February 17, 2020 Just now, XCR1250 said: Unlikely that much. 4-7? Quote Link to comment Share on other sites More sharing options...
FrankieJames7 Posted February 17, 2020 Share Posted February 17, 2020 2 hours ago, ACE said: 4-7? so if you get squish band perfect, and that allows for x amount more compression or timing advance, that's where the real gains are at Quote Link to comment Share on other sites More sharing options...
spin_dry Posted February 17, 2020 Share Posted February 17, 2020 18 hours ago, XCR1250 said: Too loose slows it down, years ago 2 strokes didn't have/use a squish band. I use solder or clay to determine what I want to get to then mill or Lathe cut more to get there. I’d use solder as well. The 660 Polaris motors worked well with a squish of .050”. Eric Gorr milled a head that cut it down to .040. He also reworked the chamber. The motor had incredible mid range but laid down a bit on top end. It ran good with that head until some less than ideal gas burned it down. I recut the head to .050 and regained the top end. Lesson: gain some lose some. Did you know Larry Rugland? Quote Link to comment Share on other sites More sharing options...
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