Prince is the codename for a family of automobile straight-4 engines developed by PSA Peugeot Citroën and BMW.It is a compact engine family of 1.4–1.6 L in displacement and includes most modern features including gasoline direct injection, turbocharging, BMW VANOS and variable valve timing.. The BMW variants of the Prince engine are known as the N12, N13, N14, N16 and N18.