found an actual CR calculator

[bob442]

http://kb-silvolite.com/calc.php?action=comp

incase its usefull to anyone aside me.

[Alxsmt]

i like the dynamic compression part. i should figure out what mine is someday lol. always been kinda curious

[bszopi]

That is no different than the one we have on the site, with the exception of the dynamic CR. But, you can ask Ben, there is no real way to accurately calculate the dynamic CR as it is an ever changing variable.

I actually created a version of the site CR calc that has dynamic CR, but opted not make it permanent.

Dynamic compression is not fixed, so I don't buy into those numbers meaning anything. Compression changes based on trapped mass, which changes based on valve events, intake design, exhaust design, and stroke/rod length along with temps and air/fuel mixture quality, etc.

And the intake closing value for 2 cams can be identical but they can have different opening and overlap values with the exhaust, which changes everything again. Not all cams have symettrical lobes. Some ramp up fast and close slower, and the other way around. I saw no mention of this making a difference to their formula. Dynomation doesn't agree with what they say and it goes against everything I read prior regarding dynamic compression ratio being dynamic, not static. Dynamic compression changes with RPM.

[ForcedFirebird]

The calcs don't match the site.

3.622" bore
3.307" stroke
8cc dish pistons
.06" head gaskets with 3.8" bore
32.4cc head chambers
.01" above deck

Should be about 11.56:1, that site says 12.2:1 (Ban built a DOHC flat top piston and 3500 head combo) that was 12.6:1...what one is correct?

[ForcedFirebird]

Here's the closest one I found (just have to convert cc's to ci's or vice-versa).

Either way, it's spot on with the site, but I have calculated 11.56:1

http://www.widgetbox.com/widget/compression-ratio-calculator