I have been trying to determine the efficiency of an ideal Otto cycle based on the compression ratio of my car and the heat of combustion of gasoline and I think I'm not entierly wrong but there is something quite off. When trying to calculate the temperature of the combustion stage my result gives me the amazingly high temperature of 51,621kelvin which is obviously silly. Here is the data I used: I used the heat of combustion of gasoline, in this case 42,500 Kj as Qin. 662.385kelvin as the temperature of the previous stage of the cycle. 0.834 Kj/KgK as the sepecific heat of air. So according to me the temperature should be given by the following equation: Qin=CvΔT So I need one of the temperatures so it becomes: T3=(Qin/Cv)+T2 Which translates to: T3=(42,500/0.834)+662.385 And finally: T3= 51,161kelvin I suspect that I'm using the wrong number for the specific heat of air but I'm not entierly sure, any ideas?