The is the difference between the volume in the combustion chamber above the piston when the piston is at bottom dead center (bdc) and the volume of the combustion chamber above the piston when the piston is at top dead center (tdc).

Compression ratio

Explanation:

Let's begin by explaining that in a combustion chamber there are pistons that move up and down within cylinders. If we take as an example one cylinder, we will have the following:

-The bottom dead center (BDC) is when the volume in the combustion chamber is the greatest, because the piston is exactly at the bottom of the cylinder.

- The top dead center (TDC) is  when the volume in the combustion chamber is the lowest, because the piston is at the top (the highest point) inside the cylinder.

Now, the ratio between these two volumes is the Compression ratio.

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4900=490xh

h=10