# Why constant volume combustion gives higher energy than constant pressure?

I have noticed when I have done some combustion equilibrium that enthalpy is higher when doing a constant volume combustion than pressure constant combustion.

Why is it so ? What are the reasons explaining that ?

Is it because at constant pressure combustion the variation of enthalpy is equal to heat transfert $$\Delta H = Q$$ whereas at constant volume combustion the variation of enthalpy is $$\Delta H = Q + V\Delta p$$ ?

If so that suppose that heat transfer $$Q$$ is the same for both constant pressure and constant volume combustions. Is that so ?

Thank you