Page 167 - Understanding Automotive Electronics

2735 | CH 5 Page 154 Tuesday, March 10, 1998 11:10 AM

5 THE BASICS OF ELECTRONIC ENGINE CONTROL

Figure 5.3
Intake System with
Throttle Plate

units are sometimes used, in which engine power is given in kilowatts (kw)
and air mass is given in kilograms (kg). In mathematical terms we can write:
P = KM
b A
where
P = power from the engine (hp or kw)
b
M = mass air flow rate (kg/hr)
A
K = constant relating power to air flow (hp/kg/hr)
Of course, it is assumed that all parts of the engine, including ignition timing,
are functioning correctly for this relationship to be valid.
We consider next an electronic engine control system that regulates fuel
flow to the engine. An electronic engine control system is an assembly of
electronic and electromechanical components that continuously varies the fuel
and spark settings in order to satisfy government exhaust emission and fuel
economy regulations. Figure 5.4 is a block diagram of a generalized electronic
engine control system.

154 UNDERSTANDING AUTOMOTIVE ELECTRONICS