The interface model allows to extrapolate the pressure cycle of any PFI spark ignition engine. The code uses a library that allows you to solve the energy balances in the combustion chamber divided into two zones (burnt and unburnt) by adding detailed thermodynamic properties. In the model it is possible to vary the valve timing by simulating the VVT and the VVA (Miller cycle, Atkinson Cycle). It is also possible to establish downstream of the pressure cycle if self-ignition (knocking) conditions are found, simulating the end-gas phenomenon.