Abstract: The present study focuses on the effect of air-fuel ratio and instantaneous behavior on crank angle of four cylinder direct injection hydrogen fueled engine. GT-Power was utilized to develop the model for direct injection engine. Air-fuel ratio was varied from rich limit (AFR = 27.464) to a lean limit (AFR = 171.65). The rotational speed of the engine was varied from 2500 to 4500 rpm. It can be seen from the obtained results that the air fuel ratio are greatly influence on the Brake Mean Effective Pressure (BMEP), Brake Efficiency (BE), Brake Specific Fuel Consumption (BSFC) as well as the maximum cylinder temperature. It can be seen that the decreases of BMEP, BE and maximum cylinder temperature with increases of air fuel ratio and speed, however increases the brake specific fuel consumption. For rich mixtures (low AFR), BMEP decreases almost linearly, then BMEP falls with a non-linear behavior. It can be observed that the brake thermal efficiency is increases nearby the richest condition (AFR ≅ 35) and then decreases with increases of air fuel ratio. Maximum of 35.4% at speed 2500 rpm can be seen compared with 26.3% at speed 4500 rpm. The optimum minimum value of BSFC occurred within a range of AFR from 38.144 (θ = 0.9) to 49.0428 (θ = 0.7) for the selected range of speed. The effect of the rotational speed on the instantaneous behavior of the cylinder pressure is no significant. The flame development, propagation and termination period consumes about 5 and 90% of the air fuel mixture and finally flame termination period which consumes about the rest of the mixture (5%). The present contribution suggests the direct injection fuel supply system as a strong candidate for solving the power and abnormal combustion problems.