The author recommends the testing of the vthicle on the coastdown from 50 or 40 km/h to 20 km/h when a long horizontal highway section is not available. This eliminates the speed of 20 km/h to zero, at which the variation of parameters increases by 3-4 times. Checks as for acceleration should be implemented with the III and II gears and the diagnosis of the engine condition should be carried out according to the worst outcome.
At road coast-down test of Chevrolet Aveo sedan the aerodynamic drag coefficient Cd = 0,367 and the coefficient of rolling resistance = 0,0143 is defined. The reference values of coast-down are calculated. There have been revealed discrepancies between the real slowdowns and the calculated ones.
Oscillations give rise to additional resistance to movement of the car about 7 Hz, and possible a partially reduction of resistance in the zone of high-frequency resonance of about 18 Hz.
The nature of the real dependence of the movement resistance of a passenger car speed during the free coast-down is significantly different from the theoretical one. Partially, the differences can be eliminated by taking into account the loss of transmission idling.
Oscillations give rise to additional resistance to movement of the car about 7 Hz, and possible a partially reduction of resistance in the zone of high-frequency resonance of about 18 Hz.
The nature of the real dependence of the movement resistance of a passenger car speed during the free coast-down is significantly different from the theoretical one. Partially, the differences can be eliminated by taking into account the loss of transmission idling.
It is proposed to measure a vehicle running-out way from high and low speed, evaluate deceleration and with earlier received formulae to determine rolling and air resistance coefficients.
Formulae for calculation of wind speed and factors of air and rolling resistance by results of run-down in two opposite directions are deduced and confirmed experimentally.
