Measuring barometric pressure with a manifold pressure sensor in a microprocessor based engine control system

In a microprocessor based electronic engine control system for an internal combustion engine, a method for updating the stored ambient pressure signal by measuring the ambient barometric pressure during engine operation using a manifold pressure sensor, the method comprising the steps of:

• generating timing signals indicating the rotational position of an engine member and including a signal indicating a predetermined rotational position in the rotation of said engine member;
• generating a pressure signal from the manifold pressure sensor representing the pressure surrounding the sensor in response to said predetermined rotational position;
• reading the value of ambient barometric pressure stored in the memory of the microprocessor;
• comparing the value of the barometric pressure stored in the memory of the microprocessor and the value of said pressure signal;
• increasing the value of the barometric pressure by one unit to generate a new barometric pressure value when the value of said pressure signal is greater than the value of the barometric pressure;
• comparing the new barometric pressure value with a predetermined fixed constant representing the maximum barometric pressure;
• and
• storing in the memory of the microprocessor either the new barometric pressure value if equal to or less than said fixed constant or the value of the maximum barometric pressure if the new barometric pressure value is greater than said fixed constant.

In a microprocessor based electronic engine control system for an internal combustion engine, a method for measuring the ambient barometric pressure during engine operation using a manifold pressure sensor, the method comprising the steps of:

• generating timing signals indicating the rotational position of an engine member and including a signal indicating a predetermined rotational position in the rotation of an engine member;
• generating a pressure signal from the manifold pressure sensor representing the pressure surrounding the sensor in response to said predetermined rotational position;
• reading the value of ambient barometric pressure stored in the memory of the microprocessor;
• comparing the barometric pressure stored in the memory of the microprocessor and the value of said pressure signal;
• generating a control signal when the value of barometric pressure is greater than the value of said pressure signal;
• determining both the throttle valve position and the speed of the engine;
• generating an engine signal in response to a wide open throttle and an engine speed less than a threshold speed;
• decreasing the value of the barometric pressure by one unit to generate a new barometric pressure value in response to the simultaneous occurrence of said control signal and said engine signal;
• and
• storing in the memory of the microprocessor the new barometric pressure value.