Ok I tried a search but came up with a lot of stuff but not specific to my question on compression ratio.


I often see compression ratios of 11:1 or 12:9:1 and what not.

I believe to come up with these figures you divide the cubic volume within a cylinder of the motor at TDC by the volume at BDC.

So for instance if you get 100cc's at TDC and 20cc's at BDC then you have 10:2. I read this off some other thread on this site.

But my question is why do some ratios have a number in the middle like 12:9:1? What does the 9 mean?

Also I assume the higher the first number the more power the motor can produce, how are the other numbers fit into the equation as far as what is better or worse?

For instance would 11:2:1 compression be better than 11:3:1 or vice versa?

Thanks for your insight.

 

it actually tells you the math equation for figuring this out in the CTR/PCT piston sticky post here in the all motor forum. or check out c-speedracing.com for the comp calculator, its not correct on ctr piston comp but everything else is close.

 

its actually 11.5:1 or 11.2: or 12.4:1 and so on. if you ever see 12:5:1 its just a typo.

makes sense? there is no 11:5:1

eleven point five to one, is how you would read it. NOT eleven to five to one.

hope that helps a little

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by chameleon &raquo;</TD></TR><TR><TD CLASS="quote">it actually tells you the math equation for figuring this out in the CTR/PCT piston sticky post here in the all motor forum. or check out c-speedracing.com for the comp calculator, its not correct on ctr piston comp but everything else is close.</TD></TR></TABLE>

i find that http://www.zealautowerks.com is more accurate than the c-speed calculator

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by envision2teg &raquo;</TD></TR><TR><TD CLASS="quote">its actually 11.5:1 or 11.2: or 12.4:1 and so on. if you ever see 12:5:1 its just a typo.

makes sense? there is no 11:5:1

eleven point five to one, is how you would read it. NOT eleven to five to one.

hope that helps a little</TD></TR></TABLE>


I'm still confused. What do you mean it's actually 11:5:1?
How is 11:5:1 different from 11:3:1? Or is that just another way to say 12:1? I'm so confused lol.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Reckless636 &raquo;</TD></TR><TR><TD CLASS="quote">


I'm still confused. What do you mean it's actually 11:5:1?
How is 11:5:1 different from 11:3:1? Or is that just another way to say 12:1? I'm so confused lol.</TD></TR></TABLE> I believe he was talking about how people type 11:5:1 when they actually mean 11(.)5:1. They use ( instead of the point (.) which is the correct way of using it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by drchulo &raquo;</TD></TR><TR><TD CLASS="quote"> I believe he was talking about how people type 11:5:1 when they actually mean 11(.)5:1. They use ( instead of the point (.) which is the correct way of using it.</TD></TR></TABLE>


Oh Ok that does make sense then. Thanks!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Reckless636 &raquo;</TD></TR><TR><TD CLASS="quote">


I'm still confused. What do you mean it's actually 11:5:1?
How is 11:5:1 different from 11:3:1? Or is that just another way to say 12:1? I'm so confused lol.</TD></TR></TABLE>

how is 11.5:1 different from 11.3:1?

well it is a ratio. so 11.5:1 is larger than 11.3:1

so in general, for every 1(one) of something you have 11.5 of something else. where as for every 1(one) of something you only have 11.3 of something else.(the second one is less). just look up the word ratio in reference to math, otherwise i dont know what to tell ya.

in the context we are using it it refers to compression/pressure.