to improve the efficiency.
to make it environment friendly.
to make the best use of the fuel.
to make save power.

Sure, its called a turbocharger.


http://auto.howstuffworks.com/turbo.htm

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PS In response to whoever told you an EGR was a power adder or specifically good for ''generating power'' that is not true. an EGR is an emissions item. it robs your car of power, it does not add any. an EGR block-off plate (the removal of this system!) is a normal first step in adding power to almost any motor. you should know that if your a ''performance engine builder.''

Cars already do that. Its called an EGR (Exhaust Gas Recirculation).

they do in my 86 Mustang SVO turbo, they make it faster !

has been done for over 30yrs now, especially in the diesels. they are called turbochargers. typically used with intercoolers to reduce the temperature of the compressed air before entering the cylinder.

they improve efficiency by generating 20% more power from the engine for the same fuel, resulting in better kmpl.

that same question was asked like 30-40 years ago.and they made a turbocharger, turbos are used more on desiel motors than gas, gas motors tend to have a supercharger

yeah run a turbo man. ever hear of gti's?
theyre little four cylinders run turbos for big horsepower.