Electronic Systems and Computer Technology - Decreasing Fuel Consumption and Exhaust Gas Emissions in Transportation - page 95

Fig. 6.2 Elements of a motor
vehicle's electronic system

sensors actuators

battery, starter
generator, electric devices

networking

electronic
system

on-board
hardware

auxiliary device
system

on-board
software

elements of safety
engineering

information
technology equipment

6.2 Vehicles' Electronics

In the past, fuel injection, ignition timing, idle speed, variable valve timing and
valve operation etc., were directly controlled by mechanical, pneumatic and
hydraulic sensors, and connected analog electronic modules. Electronics is one of
the most intensively developed fields in transportation [ 8 ].

6.2.1 Electronic Control Unit

The main element of the current electronic system is the Electronic Control Unit
(ECU). It is an embedded system that controls one or more of the electric and
electronic systems, and the subsystems in a vehicle. Recently developed ECUs are
equipped with a data logger which records all sensor signals using highly devel-
oped software in an on-board installed and operating micro controller system.
Some modern vehicles have up to 80 ECUs, including engine, transmission,
telephone, body, door, seat, indoor air condition, speed, convenience control units
and Man-Machine Interfaces (MMI) [ 9 ].
Current ECU technology monitors many functions in vehicle systems such as:

• The idling speed which determines the timing of the fuel injection with the
crankshaft position;
• The engine cycle which opens and closes the intake air and fuel, and exhaust gas
valves;
• The ignition which determines when the spark plugs should fire;
• The revolution limiter which limits the highest number of revolutions allowed in
the engine;
• The cooling water temperature correction which is needed to regulate additional
fuel consumption when the engine is too cold or dangerously hot;
• Transient fuelling, i.e., a specific amount of fuel when the throttle is opened;
• Fuel pressure modification which increases or decreases the timing of the fuel
injection to compensate for a drop in fuel pressure;