[raj87verma88]

Ok, Let me first welcome you to CE. Now, before I begin answering your question.
First thing. You should post your Questions in the Valid Section. In this case the Mechanical Engineering Section. You will find that a lot of people will answer your queries.
Second, Introduce yourself to the whole community. This will help you and us in knowing each other better.
Third, Please refrain from using SMS language in your posts and it will be highly appreciated if you format the post properly before posting it.

Now to your Question. The engine emits heat as the bulk of energy provided by expansion of gases goes waste in the form of Heat. If we increase the efficiency of the engine then this waste heat will be less. You can also search on ways to use this heat effectively. A friend of mine is researching on working the car's air conditioner using the waste heat.