Utilization of better source of energy is always being point of research so keeping this in mind we have written this paper. As we know natural resources such as diesel and petrol are limited in amount so, there is need to maintain their exploitation for future. The excess exploitation of natural resources (especially in our contexts diesel and petrol) is the major cause of concern in the world. In the normal design engine diesel, petrol and natural gases are being utilized. It is challenge for the scientific and the technical individuals to comment with certain fuels other than the above so that the available limited source of our natural resources are maintained. Keeping in the view above social responsibility, the following options are available- Natural air, Bio diesel, solar energy and Water etc Keeping in the view the various pros and cons of the above, it has been decided to work with natural air due to huge availability in the nature. The air driven engine may be the point of research. Air driven engine may help to reduce the demand of conventional fuels. Thus the objective of this research is to design & modify the four stroke petrol engine into the compressed air engine by modification in the cam lobes and also to evaluate the comparison of economic characteristics between compressed air engine and four stroke SI engines. By experimental investigation it is found that compressed air engine can run per kilometer at expense of 60 to 70 paisa. It is hard to believe that only air can run the engine. It seems like impossible but now days it is possible to run the engine on only air. Also now a day’s pollution is a major problem standing in front of world. Engine runs on the pure air is very good and cheaper solution on it. Pure air is vastly available on earth surface so there is no need of going anywhere for fuel. Due to these tremendous properties of air, in automobile industry air will play vital role in developing future cars. So in this paper effort is made to study various modification and merits & demerits of compressed air engine.
