Lean combustion strategy is used as a tool in the reduction of greenhouse gas emission in a natural gas fuelled engines. It also increases the thermal efficiency of the combustion. In this study, late injection and stratification effect of lean charge CNG combustion in a four stroke direct injection spark ignited engine was experimentally investigated. The fuel injection is kept at 90° Crank Angle (CA) Before Top Dead Center (BTDC) and the ignition timing at 28° CA BTDC at wide open throttle. Results from this study demonstrate that Indicated Mean Effective Pressure (IMEP), it's Coefficient Of Variation (COV), in cylinder pressure history, heat release rate and mass burn fraction all depend on the relative air fuel ratio (λ) and engine speed. With an increase in engine speed, the λ limit need to be increased so that the COV to remain well below 10. However, the IMEP was found to decrease with an increase in λ. There existed an optimum λ for each specific engine speed where the peak cylinder pressure is maximum and the crank angle corresponding to peak pressure value is retarded. © 2012 Asian Network for Scientific Information.