To solve a problem that a conventional internal combustion engine requires considerably thick fuel because of repetition of acceleration and deceleration and demand for comfort in actual travelling as a means for livelihood, and fuel economy is not particularly improved as compared with 20 years ago.

An electric heater coil arranged in parallel with an intake manifold, which liquifies valuable fuel burned up and wasted by a catalyst when the fuel is liquified and turns into exhaust heat as it is in rapid acceleration, is embedded in the intake manifold. A condition is changed by suppressing a current value and greatly improving heat retention when an air-fuel mixture brushes and passes through, and waste is avoided in actual travelling wherein even slight liquefaction is closed into a dish-shaped expansion chamber and conversion into smooth performance in engine brake effective for fuel economy performance is achieved. Therefore, contribution to comfortable travelling can be achieved, a flow rate is further increased by inducing the condition change of the air-fuel mixture to achieve complete combustion. An output of an engine main body is increased and theoretical thermal efficiency is improved to save fuel cost, reduce harmful exhaust gas, and improve comfort.