Page 163 - Understanding Automotive Electronics

2735 | CH 5 Page 150 Tuesday, March 10, 1998 11:10 AM

5 THE BASICS OF ELECTRONIC ENGINE CONTROL

correct load and inertia of the vehicle moving along a road under various
conditions. The conditions are the same as if the vehicle actually were being
driven.
Emission samples are The vehicle is operated according to a prescribed schedule of speed and
collected and measured load to simulate the specified trip. One is an urban trip and one is a highway
during a simulated trip. The schedules are shown in Figure 5.2. The 18 cycles of the urban
urban trip containing a simulated trip take 1,372 seconds and include acceleration, deceleration, stops,
high percentage of stop- starts, and steady cruise such as would be encountered in a “typical” city
and-go driving. automobile trip of 7.45 miles (12 km). The highway schedule takes 765
seconds and simulates 10.24 miles (16.5 km) of highway driving.
During the operation of the vehicle in the urban test, the exhaust is
continuously collected and sampled. At the end of the test, the absolute mass of
each of the regulated exhaust gases is determined. The regulations are stated in
terms of the total mass of each exhaust gas divided by the total distance of the
simulated trip.
Fuel consumption also is In addition to emission measurement, each manufacturer must determine
measured during the the fuel consumption in MPG for each type of vehicle and must compute the
tests. Emission and corporate average mileage for all vehicles of all types produced in a year. Fuel
MPG requirements have consumption is measured during both an urban and a highway test, and the
grown increasingly strin- composite fuel economy is calculated.
gent since 1968. Table 5.1 is a summary of the exhaust emission requirements and CAFE
for representative years. It shows the emission requirements and increased fuel
economy required. Because of these requirements, each manufacturer has a
strong incentive to minimize exhaust emissions and maximize fuel economy for
each vehicle produced.

Table 5.1
Emission and MPG
Requirements
Year Federal HC/CO/NO California HC/CO/NO CAFE MPG
x x
1968 3.22/33.0/– — —
1971 2.20/23.0/– — —
1978 1.50/15.0/2.0 0.41/9.0/1.5 18.0

1979 1.50/15.0/2.0 0.41/9.0/1.5 19.0
1980 0.41/7.0/2.0 0.41/9.0/1.5 20.0
... ... ... ...

1989 0.31/4.1/1.0 0.31/4.1/1.0 27.5

150 UNDERSTANDING AUTOMOTIVE ELECTRONICS