Primer on Automobile Fuel Efficiency and Emissions - Pollution Probe

During the late 1970s and early 1980s, North American automobiles, on average, experienced significant engine
downsizing in an attempt to curb fuel consumption (more on this in chapter five). Many models that were formerly
equipped with 8-cylinder engines now came equipped with 6- or 4-cylinder engines. Power output of engines
decreased and vehicles became smaller (lighter cars require less power to accelerate, and lose less energy upon
braking); however, this trend only lasted for a few successive model years. New technologies were soon introduced
that allowed smaller engines to produce more power without increasing the amount of fuel consumed.
These technologies included fuel injection, improved combustion chamber design, increased compression ratios,
more precise valve control, and exhaust gas recirculation. This ensures more complete combustion of the fuel,
thus increasing the amount of power produced from each drop of fuel and, depending on the technology,
reducing the amount of NOx and VOCs (HC) emissions. More efficient engine design meant newer vehicles
could meet the demand for power with smaller engines. The smaller engines also represent a significant reduction
in weight, contributing to lower fuel consumption.
Since the mid-1980s, engines continued to become more efficient producers of power. This would have led to
greater fuel savings if the engine downsizing trends had continued. Instead, engine sizes remained steady and
reductions in fuel consumption were not realized. Ongoing technology improvements led to ever-higher power
ratings among new vehicles (see Figure 3-1). For future vehicle fleets to consume significantly less fuel, smaller
engines will need to be part of the design agenda among automakers. In September of 2008, General Motors
announced that they would double their global production of small four-cylinder engines (1.0 to 1.4 litres) by
2011, with more than half of the increase happening in North America. The highlight of this plan is the manufacturing
of a 1.4 litre turbocharged engine, generating the power of a larger engine but consuming the fuel of
a small automobile.
There are numerous engine technologies available today (or in development) that will enable a small engine to
perform as would a larger engine in terms of power output, while consuming much less fuel. These technologies,
along with potential fuel consumption reductions, are listed in Table 3-2. It should be noted that these potential
reduction factors are not necessarily additive, nor are they necessarily compatible with each other.
<strong>Primer</strong> on Automobile Fuel Efficiency & Emissions
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