Experimental Test Track Methods Of Estimating Vehicle Tractive Resistance

Recently a suitable torque transducer became available which enables simultaneous measurement of torque and speed at each driven wheel. These were experimentally applied to two compact FWD vehicles for trials on a very long flat track. The object was to identify the various elements of tractive resistance; one significant advantage was that drive line losses could be measured which improved the accuracy of rolling resistance and drag coefficient estimates. The test procedure combined both drive and coastdown modes so that the results could be compared. The data analysis technique treated the ambient wind velocity component as an unknown, and was so organised as to permit testing with higher wind speeds than usual. The effect of front wheel toe setting on tractive resistance, and therefore on fuel economy, was identified. Fair correlation of drag coefficient with wind tunnel results was demonstrated.