Page 111 - 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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Engine systems 95

Figure 2.22 Petrol engine indicator diagram. Diesel fi gures are approximately double:
1, introduction; 2, compression; 3, power; 4, exhaust

Figure 2.23 Ideal, retarded and advanced ignition point
the ‘pinking’ noise. Although the noise is quite subtle, the forces are massive and
Key fact
cause considerable damage to the engine.
Overadvanced (early) or retarded
When pinking occurs, the combustion energy precipitates through the engine
(late) ignition can cause serious
components, causing damage. In addition, heat is generated that is not dissipated
damage.
normally and this causes excessive temperature of engine components (e.g.
pistons, valves and valve seats) and consequent heat-related damage.
Overretarded ignition causes incorrect timing of the energy release from the
fuel that, in turn, means less energy to do work and therefore more energy
to dissipate via the cylinder boundaries. This causes an increase in engine
temperatures, damages components and reduces overall engine effi ciency. This
excess energy also has to be rejected via the exhaust and this causes increased
exhaust gas temperatures that can damage exhaust valves and seats, as well as
exhaust gas components (catalytic converter).

2.1.2.2 Compression ignition (CI)
In a diesel engine, the compression process must create suffi cient energy to
cause the temperature of the compressed gas (air) to rise above the