Page 186 - 05. Subyek Teknik Mesin - Automobile Mechanical and Electrical Systems Automotive Technology Vehicle Maintenance and Repair (Vehicle Maintenance Repr Nv2) by Tom Denton

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170 Automobile mechanical and electrical systems

Figure 2.178 Valves

Figure 2.179 Air fi lter

because other less damaging substitutes have been found. The changes in the
fuel have necessitated the use of hardened valves and valve seats and changes
to the ignition timing and fuel delivery systems ( Fig. 2.178 ).
Air-intake systems have been developed from a simple ducting to a complex
air-fl ow design adapting to the changing speed and load conditions of the
engine. Filtration is also an important aspect ( Fig. 2.179 ).
Electronic control of the combustion process has been the key development, and
and hydrocarbon emissions. Exhaust gases
has achieved reductions in CO, NO x
are monitored by the electronic engine control module by signals sent from a
lambda, or oxygen, sensor in the exhaust ( Fig. 2.180 ). This monitoring allows fuel
and air supplies to be accurately controlled for optimum combustion.
The remaining pollutants in the exhaust gases, which cannot be eliminated or
reduced by the electronic systems, are converted into less harmful substances.
This is achieved by using a catalytic converter ( Fig. 2.181 ).

Developments to improve the atomization and the mixing of the fuel in the
incoming air stream include heating the inlet manifold, or heating the air as it
enters the inlet manifold. This is achieved by preheating the air by ducting the air
supply over the exhaust manifold ( Fig. 2.182 ).