Word Problem
 

I have a stock bottom end, redtop SR20DET with a stock compression ratio of 8.5:1. I replaced the head gasket with a 1.1mm Cosworth head gasket. What is my new compression ratio? Show your work.

Seriously I want to know the math for figuring this sort of thing out.

I fail to see how this is a word problem.

This is a word problem
"John is twenty years younger than Amy, and in five years' time he will be half her age. What is John's age now?"

Engine Compression Ratio (CR) Calculator

Right thurr...

15!

1.1 = 1.1

=>

8.5cr = 8.5cr

That is, the stock gasket is 1.1mm. You didn't change the height, so the compression didn't change.

Epstein takes the fun out of math...

For some reason I was thinking that the stock gasket was thinner than that. Thanks again Epstein

...i thought you meant you had a problem with Microsoft Word

http://media.urbandictionary.com/ima.../word-5807.jpg

what do I get for answering ph34r??

Nissan uses a bunch of different sizes for different SR apps. All the 9.5cr motors use a 0.8mm gasket. I just found out that the 10.0cr motors use a 1.6mm gasket!

The equation has a few easy steps.

(Combustion chamber volume)+(gasket volume)+(TDC piston volume)+(piston dish volume)

Number is the volume when the piston is at the top. To find the volume when the piston is at the bottom, take all that and add the cylinder volume. To get the compression ratio, it's just big number over small number.

Tips:
The comb chamber volume is going to be in cc's, so stay in that unit of measure. That is, cc = cubic centimeters = cm x cm x cm. Convert all mm measurements to cm!!!

Gasket volume is pi*r^2 times gasket thickness. Ex: 3.1415*(4.35^2)*0.11 Where a gasket diameter of 87mm -> 8.7cm -> 4.35cm radius. 0.11 is the 1.1mm thickness in cm.

TDC piston volume: when the piston is at TDC, it may be below or above the surface of the block. This either leave adds or subtracts volume. On the SR, it's 0.05mm below, so you're adding a little volume. You calculate this volume the same way as the gasket volume. Or, just add it to the gasket volume calculation to save time. Here we'd use 0.115 in the above calc, which is that extra 0.05 tacked on. The radius is 86mm instead of 87mm, but the overal imact of inserting this into the gasket calc is negligible.

Piston dish is 15cc. Head volume is 45cc.

Cylinder volume is 86mm x86mm -> 3.1415*(4.3^2)*4.3, which should give you 499.5cc's.

surprisingly I followed all that. thanks.