Flanagans twin Posted April 27, 2007 Report Share Posted April 27, 2007 how do i find out my compression ratio? thanks Quote Link to comment Share on other sites More sharing options...
J-Madd Posted April 27, 2007 Report Share Posted April 27, 2007 (edited) I don't have a clue what the compression ratio is on a 2-stroke. You can get a compression tester that screws in where the spark plug goes, hold the throttle wide open(with the key off), and kick it until the needle in the gauge stops moving. The gauge will measure your compression in PSI and/or metric equivalent (don't remember, physics was a long time ago). Edited April 27, 2007 by J-Madd Quote Link to comment Share on other sites More sharing options...
Flanagans twin Posted April 27, 2007 Author Report Share Posted April 27, 2007 yea i know how to do that haha but thanks anyways....ill look around..... hoping to have good psi! haha Quote Link to comment Share on other sites More sharing options...
MFIC Posted April 27, 2007 Report Share Posted April 27, 2007 how do i find out my compression ratio? thanks Compression ratio= volume at bottom dead center / volume at top dead center. Quote Link to comment Share on other sites More sharing options...
fastrthnu Posted April 27, 2007 Report Share Posted April 27, 2007 Compression ratio= volume at bottom dead center / volume at top dead center. http://www.rbracing-rsr.com/compstaticcalc.html we usually just go with PSI round here though. Quote Link to comment Share on other sites More sharing options...
Flanagans twin Posted April 27, 2007 Author Report Share Posted April 27, 2007 haha alright thats what i usually use is psi.. thanks Quote Link to comment Share on other sites More sharing options...
jayzx10r Posted April 28, 2007 Report Share Posted April 28, 2007 It's too bad that the calculation for 2-strokes doesn't factor in the loss of displacement due to porting. I wonder what the actual displacement is when measured above the intake/exhaust port... I bet the 450 guys would love to hear that they were roached by a 185cc mill!! Actually...if someone has a jug and can measure down to the lip of the first port they reach from the top of the cylinder and post/PM me with that measurement...I'd appreciate it!! :thumbsup: This could be fun!! Jay Form SanD. Quote Link to comment Share on other sites More sharing options...
64xracer Posted April 30, 2007 Report Share Posted April 30, 2007 It's too bad that the calculation for 2-strokes doesn't factor in the loss of displacement due to porting. I wonder what the actual displacement is when measured above the intake/exhaust port... I bet the 450 guys would love to hear that they were roached by a 185cc mill!! Actually...if someone has a jug and can measure down to the lip of the first port they reach from the top of the cylinder and post/PM me with that measurement...I'd appreciate it!! :thumbsup: This could be fun!! Jay Form SanD. You will not lose any displacement due to porting...as long as the bore and stroke stay the same the displacement will to. You will however lose compression. Quote Link to comment Share on other sites More sharing options...
fastrthnu Posted April 30, 2007 Report Share Posted April 30, 2007 You will not lose any displacement due to porting...as long as the bore and stroke stay the same the displacement will to. You will however lose compression. ummm. k. Quote Link to comment Share on other sites More sharing options...
jayzx10r Posted May 1, 2007 Report Share Posted May 1, 2007 (edited) You will not lose any displacement due to porting...as long as the bore and stroke stay the same the displacement will to. You will however lose compression. Ummmm, Ok. Let's try this another way.... If you had a cylinder with a piston/rings at bottom dead center and tried filling the cylinder with water, the water would run out through the ports. If you were to raise the piston to the point where water wouldn't escape through the ports and it would actually seal, this is the starting point of measure for volume I was eluding to. Measure from this point to TDC. I wonder what this displacement figure would be if you were to measure this volume!! I don't think displacement is relative to compression...but I think combustion chamber size is the significant factor though... I can't believe the riding season is over already.... :verymad: Jay From San D. Edited May 1, 2007 by jayzx750 Quote Link to comment Share on other sites More sharing options...
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