Equus 3110 - CanOBD2 Diagnostic Tool - Manual (Page 16)

14 CAN OBD2
E
Onboard Diagnostics
COMPUTER ENGINE CONTROLS
COMPUTER ENGINE CONTROLS
The Introduction of Electronic Engine Controls
As a result of increased air pollution (smog) in large
cities, such as Los Angeles, the California Air Resources
Board (CARB) and the Environmental Protection Agency
(EPA) set new regulations and air pollution standards to
deal with the problem. To further complicate matters, the
energy crisis of the early 1970s caused a sharp increase in
fuel prices over a short period. As a result, vehicle manufac-
turers were not only required to comply with the new emis-
sions standards, they also had to make their vehicles more fuel-
efficient. Most vehicles were required to meet a miles-per-gallon
(MPG) standard set by the U.S. Federal Government.
Precise fuel delivery and spark timing are needed to reduce vehicle
emissions. Mechanical engine controls in use at the time (such as igni-
tion points, mechanical spark advance and the carburetor) responded
too slowly to driving conditions to properly control fuel delivery and
spark timing. This made it difficult for vehicle manufacturers to meet
the new standards.
A new Engine Control System had to be designed and integrated with
the engine controls to meet the stricter standards. The new system had
to:
■ Respond instantly to supply the proper mixture of air and fuel for
any driving condition (idle, cruising, low-speed driving, high-speed
driving, etc.).
■ Calculate instantly the best time to “ignite” the air/fuel mixture for
maximum engine efficiency.
■ Perform both these tasks without affecting vehicle performance or
fuel economy.
Vehicle Computer Control Systems can perform millions of calcula-
tions each second. This makes them an ideal substitute for the slower
mechanical engine controls. By switching from mechanical to elec-
tronic engine controls, vehicle manufacturers are able to control fuel
delivery and spark timing more precisely. Some newer Computer
Control Systems also provide control over other vehicle functions,
such as transmission, brakes, charging, body, and suspension sys-
tems.
Electronic Computer Control Systems make it possible
for vehicle manufacturers to comply with the tougher emis-
sions and fuel efficiency standards mandated by
State and Federal Governments.