This engine has been developed to achieve lean combustion. A prechamber which is named as the Turbulence Generating Pot (TGP) was developed to extend the lean misfire limit and also to increase flame propagation velocity. The lean misfire limit and the combustion velocity depend on the configuration of the TGP and also on the spark plug location. The jet flame from the TGP creates a strong turbulence in the main combustion chamber resulting in a high velocity propagation of the flame. NOx emission is reduced to a minimal level due to the strong turbulence generated by the TGP.