PURPOSE: To make it possible to measure the flow rate of intake air by using a hot wire type air flowmeter, by providing a buffer chamber and the like in an intake air path between a compressor turbine of a turbo charger and a flow rate detecting means of the hot wire type air flowmeter.

CONSTITUTION: A tubular buffer chamber 14 is communicated and connected at the intermediate part of an intake air path 2 between a compressor turbine 10B and a flow rate detecting means such as a hot wire 11A. The chamber 14 absorbs the intake air pulsation yielded in the path 2. It is desirable that the cross sectional area of the opening of the buffer chamber 14 is about 1.5 times or more the cross sectional area of the opening of the intake air path 2. In this way, the intake air pulsation is effectively absorbed and does not act on the hot wire 11A an the like. Therefore, the hot wire type air flowmeter can measure the flow rate of the intake air accurately all the time regardless of the operating state of the engine.