The efficiency of the Otto cycle, which is a theoretical thermodynamic cycle that models the operation of a typical spark-ignition internal combustion engine, can be calculated using the following formula:
Efficiency = 1 - (1 / compression ratio)^(specific heat ratio - 1)
In this formula, the compression ratio refers to the ratio of the maximum volume to the minimum volume in the engine's cylinder, and the specific heat ratio (also known as the heat capacity ratio or adiabatic index) represents the ratio of specific heat capacities at constant pressure and constant volume for the working fluid (usually air).
It's important to note that the specific heat ratio and the compression ratio depend on the specific design and characteristics of the engine being considered. Typical values for the specific heat ratio for air range from around 1.3 to 1.4, and the compression ratio for gasoline-powered automotive engines typically falls within the range of 8:1 to 12:1.
Using these values, the efficiency of the Otto cycle can be calculated. However, without specific values for the compression ratio and specific heat ratio, it is not possible to provide an exact efficiency value.