Evaluation of Potential Benefit of 6 × 2 Over 6 × 4 Drive Mode to Improve the Fuel Economy on Heavy Commercial Vehicle

Reduction in the drivetrain losses of a vehicle is one of the important contributing factors to amplify the fuel economy of vehicle, particularly in heavy commercial vehicle. The conversion of 6 × 4 drive vehicle into 6 × 2 drive has a benefit of improving the fuel economy of a vehicle by reducing the drivetrain losses occurring in the second rear axle. It was cultured by calculation that in 6 × 2 drive the tractive force available at the wheels, of heavy commercial vehicle with GVW of 44 tons and above, will be much higher than the frictional force transmission capacity of tires, when the engine is producing peak torque on the driving duty cycle like going on steep gradient road. In such situations the tires will start to slip and may result in deteriorating the fuel economy and excessive tire wear. On the other side the flat road driving duty cycle in 6 × 2 drive will give better fuel economy than 6 × 4 drive. It was possible to get the overall fuel economy benefit, if an option is available with the driver to change the drive depending on the type of driving duty cycle. To demonstrate this, a test plan was prepared for evaluation of fuel economy on a heavy commercial tractor-trailer vehicle in different drive and different driving duty cycle. A master route for these trails was selected which comprises of flat road, steep downhill, steep uphill and city portion. It was concluded from the analysis of fuel economy trials that the vehicle with 6 × 2 drive will have better fuel economy than 6 × 4 drive on the flat road driving duty cycle, city road driving duty cycle, unladen condition and in coasting mode. The steep uphill driving duty cycle requires 6 × 4 drive mode. In this exercise one of the essential bi-product was the learning of effect of tire temperature on fuel consumption of the vehicle. The investigation has shown that the higher tire temperature drastically increases the fuel consumption of a vehicle irrespective of type of driving duty cycle.