Effects of altitude in the performance of a spark ignition internal combustion engine

Ecuador’s geography is very irregular, each region is at a different altitude, rising from sea level to more than 2800 m above sea level. In this sense, the altitude variable becomes important in the behavior of an internal combustion engine. In this work, the behavior of an internal combustion engine with indirect electronic injection is studied at different heights above sea level to facilitate diagnostic tasks. This behavior is determined through the signals emitted by the absolute pressure sensors of the intake manifold and the throttle position, obtained in 11 places with a difference of approximately 500 m in altitude up to 4500 m above sea level. Analysis of these signals indicates the MAP sensor voltage variations are approximately 0.38 V per 1000 m and the engine vacuum decreases approximately 7.7 kPa per 1000 m of the head. Furthermore, the correction ratio made by the electronic control unit ECU on the pulse width and the ignition advance with the height has been determined. These results generated by this research work are important to understand the behavior of engines at altitude and facilitate automotive diagnosis.