Comparison of engine power correction factors for varying atmospheric conditions

This work evaluates proposed methods to correct engine power output as a function of atmospheric conditions. The analysis was made through experiments carried out in a vehicle on the road, under different temperature, pressure and air humidity conditions. The vehicle had a four-cylinder gasoline-fuelled engine, with multi-point fuel injection system, variable intake pipe length and variable intake valve camshaft position. The vehicle was tested at sea level and at 827 m above sea level, corresponding to atmospheric pressures between 1027 and 926 mbar. Air temperature varied from 22.8 to 33.8°C at the test locations. The measured performance parameter in the tests was the vehicle acceleration time. The acceleration times from 0 to 400 m, 0 to 1000 m, 40 to 100 km/h and 80 to 120 km/h were all recorded, leaving from an initial vehicle speed of 40 km/h. The engine power curve obtained in laboratory under a standard ambient condition was corrected to the conditions of the road tests by the correction factors proposed by the methods under evaluation, and the corresponding acceleration times were calculated and compared with the measurements from the road tests. The evaluated methods for power correction were the following: DIN 70020, SAE J 1349, JIS D 1001 and ISO 1585. The SAE J 1349 method provided the best approach between the experimental and calculated acceleration times.