The concept of increasing the fuel efficiency of a petrol engine in this project, is to pre-heat the intake air which is flowing through the carburetor.  The humidity in the atmospheric air affects the petrol vapourisation in the carburettor.  Therefore, by pre-heating the inlet air to the carburettor for a considerable amount, the vapourisation can be ease and in turn complete combustion is achieved.  Moreover by reducing the water vapour to the engine, the steam formation in the engine can be reduced pitting of the engine cylinder, piston and exhaust pipe.


The pre-heating of inlet air to the engine can be achieved by fixing a heat exchanger inside the exhaust pipe.  The atmospheric air is sucked through the heat exchanger to the carburettor.  The air which is flowing though the heat exchanger gets heated by the engine exhaust gas.  This reduces the water vapour in the inlet air and the temperature of the air is raised.  The temperature raise causes complete combustion in the engine and it is also more suitable for warming up the engine in cold conditions.





The heat exchanger is located in the engine exhaust pipe.  The exhaust pipe consists of a muffler and stay plates etc.  The heat exchanger is made up of 18 SWG M.S. plate. The inner tube is inserted tightly on the muffler tube.  A spiral baffle plate arrangement is made in between the two concentric tubes so as to make a spiral path to the incoming air.  So that the heat transfer to the air can be increased.  Moreover the air is flowing in counter direction to the exhaust gas; thereby effective heat transfer can be achieved.


The heat exchanger inlet is fitted with a pre-filter.  The outlet is connected to a by-pass mechanism through a hose pipe.  The by-pass mechanism is connected to the carburettor intake. The temperature of the air entering to the carburettor can be maintained constant for a particular degree centigrade.  When the temperature of air is increased above the predetermined valve the thermal relay opens the butterfly valve (4- wheeler Application) and allows the atmospheric air to mix with the heater air from the heat exchanger.  So the hot air is diluted with atmospheric air and reducing the temperature.