Specific heat in for the Otto cycle

[dinoclaro]

A class project requires us to model the Otto cycle using ideal gas properties. We are not given the value for qin (specific heat in) and are told to make an intelligent approximation. My approach to this has been to find the calorific value of petrol, multiplying this by the density of petrol in which I then get the specific calorific value. I then proceed to multiply this by the volume of fuel in the cylinder (Volume at BDC divided by the air to fuel ratio). At the end of this process I get a value of around 980.35 J and cannot think of any way of converting this to specific heat as dividing by the mass obviously just returns the initial calorific value.

We are required to optimize the process using excel solver where the compression ratio and qin are the variables. Therefore this initial approximation has no bearing on the final optimized value (qin = 400Kj/Kg) . Although we are required to give an explanation of our initial value.

I fear that I am not understanding the Otto cycle process of where heat is introduced. Is there another way I should approach this problem?

 

[jack action]

The air-fuel ratio is a mass ratio.