MAP sensor data can be converted to air mass data using the speed-density method. Mass air flow sensor pdf II equipped General Motors engines. The following example assumes the same engine speed and air temperature. WOT due to the higher barometric pressure.
The engine requires the same mass of fuel in both conditions because the mass of air entering the cylinders is the same. The higher absolute pressure in the intake manifold increases the air’s density, and in turn more fuel can be burned resulting in higher output. Engine vacuum is the difference between the pressures in the intake manifold and ambient atmospheric pressure. Engine vacuum is a “gauge” pressure, since gauges by nature measure a pressure difference, not an absolute pressure. The engine fundamentally responds to air mass, not vacuum, and absolute pressure is necessary to calculate mass. Note: Carburetors are largely dependent on air volume flow and vacuum, and neither directly infers mass. Some manufacturers use the MaP sensor to accomplish this.
In these vehicles, they have a MAF sensor for their primary load sensor. The MaP sensor is then used for rationality checks and to test the EGR valve. EGR valve and then monitor the MaP sensor’s values. If the EGR is functioning properly, the manifold absolute pressure will increase as exhaust gases enter.
This page was last edited on 21 December 2017, at 06:26. Flow can be measured in a variety of ways. Positive-displacement flow meters accumulate a fixed volume of fluid and then count the number of times the volume is filled to measure flow. Other flow measurement methods rely on forces produced by the flowing stream as it overcomes a known constriction, to indirectly calculate flow. Flow may be measured by measuring the velocity of fluid over a known area.