Here is one method for determine Qin from given information for an engine.
For an automotive engine, the power per liter is given as 3.37x104 W/liter, which is equivalent to 34 MW/m3 after a unit conversion. Doubling this value to include heat transfer results in approximately 60 MW/m3.
Next we need to determine the heat input in Joules for one cycle. Given that the engine speed, w, is 5000 rpm:
If we are given the bore and the stroke to be:
The displacement volume, Vd, can be found from: