Vehicle Powertrain Systems

Chapter 5

Fuel Consumption

5.1 Introduction

Fuel efficiency and emissions have become extremely important issues in the design of automobiles in order to reduce petroleum consumption and emissions that result in greenhouse effect and global warming. Overall, there are three phases involved in the conversion of fossil fuels to the delivery of useful work in controlling the motion of the vehicle in typical driving conditions. Two of these were introduced and discussed in Chapter 1 and described as:

• well-to-tank (see Figure 1.1a); Figure 1.1
• tank-to-wheels (see Figure 1.1b)

The third phase involves the conversion of power delivered at the vehicle wheel into useful work to power the vehicle over its range of normal operating conditions. Further energy losses are associated with this phase, in particular, due to tyre rolling resistances, aerodynamic drag and friction of the non-driven rotating components. Analysis of the vehicle powertrain system in typical driving scenarios depends heavily on the details of the driving schedule, involving grades, stop-start progress, traffic, acceleration and deceleration phases, etc. Consequently, there has been a lot of interest worldwide in developing standard driving cycles. These claim to be representative of typical driving conditions in different countries in, for example, urban, mixed urban, highway conditions, and they provide reference conditions so that different vehicles can be compared on a fair basis.

This chapter focuses on the second ...