 Supplying the fictitious values

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In the Otto cycle, there is no heat transfer during the process 1–2 and 3–4 as they are isentropic processes.Heat is supplied only during the constant volume processes 2–3 and heat is rejected only during the constant volume processes 4–1.The above values are absolute values that might, for instance, have units of joules (assuming the MKS system of units are to be used) and would be of use for a particular engine with particular dimensions.