Page 175 - Understanding Automotive Electronics

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5 THE BASICS OF ELECTRONIC ENGINE CONTROL

Figure 5.8
Typical Variation of
Performance with a
Variation in Air/Fuel
Ratio

FPO

Operation at or near MBT is desirable since this spark timing tends to
optimize performance. As will be explained, engine control strategy involves
regulating fuel delivery at a stoichiometric mixture and varying ignition timing
for optimized performance. However, there is yet another variable to be
controlled, which assists the engine control system in meeting exhaust gas
emission regulations.

Figure 5.9
Typical Variation of
Performance with
Spark Timing

FPO

162 UNDERSTANDING AUTOMOTIVE ELECTRONICS