If the volume of a cylinder is 70 cubic inches at bottom center and 10 cubic inches at top of the cylinder, what is the compression ratio?

The compression ratio is calculated using the formula:

Compression Ratio (CR) = Volume at Bottom Dead Center (BDC) / Volume at Top Dead Center (TDC).

In this scenario, the volume at the bottom center (BDC) is given as 70 cubic inches, and the volume at the top center (TDC) is 10 cubic inches. Plugging these values into the formula gives:

CR = 70 cubic inches / 10 cubic inches = 7.

This means the engine compresses the air-fuel mixture from a volume of 70 cubic inches down to 10 cubic inches, resulting in a compression ratio of 7:1. Essentially, this indicates that the volume of the cylinder decreases by seven times from the BDC to the TDC, which is characteristic of how compression ratios are defined and utilized in assessing engine performance and efficiency.

In summary, the calculation aligns with the basic understanding of how to determine the compression ratio in a reciprocating engine.