Mass Air Flow Meter-Design and Application

Modern fuel metering systems are designed to reduce fuel consumption and exhaust gas emissions in internal combustion engines to meet future emission legislation limits. The first step to achieve this aim is to obtain extremely precise information about cylinder charge conditions specially under dynamic engine operation.

In this paper some methods of intake air flow sensing will be compared and a new mass air flow meter of the hot film type will be presented. It is shown that the arrangement of the air flow meter within the intake manifold system greatly influences cylinder charge sensing. Methods are presented to reduce manifold filling effects. Special work is done on the dynamic response of mass air flow meters with respect to rapid load changing and air temperature fluctuation. To overcome steady-state pulsations especially with ram pipe manifolds without limiting dynamic response, this paper shows a way to minimize these problems by working up the signals in the ECU.