CR calculation, deck height/effective dome volume?
YR, thanks for the reply. The formula I've always used is CR= SV+CCV+HGV+DHV+EDV divided by CCV+HGV+DHV+EDV. Since I've never had domed or above deck pistons, i've just ignored the EDV. The only Chrysler engine book I have is the old DC one, and it doesn't go into great detail about formulas, but it does refer to the 1/2 or 1" down method. I'm just not understanding how pushing the piston down .250", filling the cylinder, and subtracting a volume equal to the mathematical volume of area x 250" (Larry Shepard compares it to a "disc") isn't correct. Which lets me ignore the negative EDV number, at least in my case. Thankyou for your time and patience.
Your math looks hard to me. It's really vbdc/vtdc. So, add up all the stuff you have, like chamber volume, head gasket and dome/dish volume. Then determine the volume of your cylinder. Then add that to your other volume an and device the two.
I'm pretty simple, so I like simple math, also here is what I'd say it looks like, in easy math.
The total of your volume is 100 cc's for the chamber. The total cylinder volume is 900 cc. Add the two together for 1000 cc's
Now it's simple math...1000/100 equals 10:1
As to the disc part of the Shepard book, you have to account for the flat part of the piston that sticks above the bore. Since my piston is .045 out, once you do the downfill, you have to calculate the flat of the piston.
So the math would be bore squared times 12.87 times the stroke, or thickness. It's the same math for figuring gasket volume.
So, bore squared is 4.04 times 4.04 equals 16.3216 times 12.87 equals 210.05899, then times the stroke, or thickness, or positive deck, times .036 equals 7.5621236 cc's for just the .036 that is out of the bore.
Now that I have totally screwed up your day with math, I'll leave you to your calculations!!!
Really, the math is much more simple in the Chrysler book. You just need to account for the "disc" that is the piston out of the hole. You calculate it like gasket thickness.