Page 24 - Understanding Automotive Electronics

2735 | CH 1 Page 11 Tuesday, March 10, 1998 10:52 AM

AUTOMOTIVE FUNDAMENTALS 1

ENGINE CONTROL

Control of the engine in any car means regulating the power that it
produces at any time in accordance with driving needs. The driver controls
engine power via the accelerator pedal, which, in turn, determines the setting of
the throttle plate via a mechanical linkage system. The throttle plate is situated
in the air intake system (Figure 1.7). The intake system is an assembly of pipes or
passageways through which the air flows from outside into each cylinder. The air
flowing into the engine flows past the throttle plate, which, in fact, controls the
amount of air being drawn into the engine during each intake stroke.
As we will show in later chapters, the power produced by the engine is
proportional to the mass flow rate of air into the engine. The driver then controls
engine power directly by controlling this air mass flow rate with the throttle plate.
Of course, the power produced by the engine depends on fuel being
present in the correct proportions. Air combines with fuel in the fuel metering
device. This device automatically delivers fuel in the correct amount as
determined by the air flow.
The classic fuel metering device was the carburetor, which is now virtually
obsolete. In modern car engines, fuel injectors do the fuel metering. The
amount of fuel delivered by a fuel injector is determined electronically in

Figure 1.7
Intake Manifold and
Fuel Metering
FPO

UNDERSTANDING AUTOMOTIVE ELECTRONICS 11