Overview

This chapter will describe how passenger vehicles are characterised first as to drag and rolling resistance coefficients and second according to fuel economy over standard drive cycles. Vehicle data necessary to compute rolling resistance and aerodynamic drag coefficients are taken from coast down tests. This procedure is further described in Chapter 11 along with some actual test data about how this applies to characterising the hybrid propulsion system. In this chapter the various standard drive cycles employed in various geographical and demographic areas are compared and rationale given for their selection.

Coast down testing is a procedure long in existence to extract the vehicle tyre and body aerodynamic drag characteristics. A coast down test procedure consists of accelerating the vehicle to a prescribed speed on a straight and level road course, holding a set speed and then, with the vehicle in neutral allowing it to coast down naturally. The test is then repeated in the same manner from the opposite direction to average out any inconsistencies due to relative wind velocity and road grade.

It is important to understand the need to accurately characterise a vehicle in terms of fuel economy and emissions by also understanding how efficiently the fuel is delivered to the vehicle's fuel tank in the first place and the type of fuel being used. A recent US House of Representatives bill on hybrid incentives has not renewed existing incentives on gasoline-hybrid, but has introduced new incentives for CIDI-hybrid [1]. The new incentive allows up to...