The development of internal combustion engines requires equipment for performance measurement. The increase of the torque and power is directly proportional to the increase of the air mass admitted for engine. The objective of this work is to confection a low cost air flow meter. With the purpose to identify when modifications in the engines are made the positive and negative results. The air flow was measured by an orifice plate, and calibrated with hot wire anemometer with maximum uncertainty of the measurement of 2.5%.