Anybody know of a good yet free online dynamic compression ratio calculator? All I can find are ones for v-8s.

Thanks.

Thanks. Now I have to figure out how to get that program to run on my Mac.

Okay, I got it to work, and I calculated my dynamic stroke length, my cam timing and overlap, and my static compression. But how do I turn any of these numbers into a dynamic compression ratio?

Okay, nevermind. I guess it helps to read the instructions on the webpage.

I use that one consistently, and it's a good tool for looking over "future builds".

How'd your engine build turn out?

-D.Idiot

I am finishing up the last few calculations for getting the head decked to achieve an 8.2 dynamic compression ratio.

I would appreciate it if someone could check my math.

I am using the a cam ground to match the Erson RV10 profile. The cylinders are .030 oversize. I have 56 cc combustion chambers (surprisingly they are all the same).

I have calculated that I need 40 cc combustion chambers to bump the dynamic compression ratio from the current 6.9 up to 8.2. In other words, I need to remove 16 cc of volume from the combustion chambers.

Assuming the lowest portion of the combustion chamber is a perfect circle (which I know isn't true due to the factory notched for the valves, but it is close enough), I need to use the following formula to calculate how much I need shaved off:

The volume of the cylinder = pie X radius of the cylinder squared X height of the cylinder

I need to remove 16 ccs, so

16 = pie X radius squared X height

Pie is a constant
16 is a known variable
radius = 3.4 inches / 2 (or, to keep it simple and to keep the units constant, 8.628 cm/2). So, R=4.314cm

So,

Height cm = 16/ (pie X (4.314 squared))

Height cm = .273659058471 cm

So

Height inches = .1077397868

SO! I need to mill .100 inches off the head. Right?

I just would cheat and use Doc's number from the stroker article (It hasn't let me down yet!!!)


so 16CC * .0066 =.1056....

.1077 is on the money...

.100 would be fine...

-D.Idiot

Cool! Thanks Rob! Good to know I still gots my math skills!

http://www.rbracing-rsr.com/calculations.htm
Here's the one I used Reed.

_________________
Cheers!
Al T

Thanks Al!