Page 98 - 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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82 Automobile mechanical and electrical systems

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Figure 2.1 Internal combustion engine Figure 2.2 Diesel and petrol engine: pistons at bottom dead centre (BDC) before start of the
internal components: 1, crankshaft; compression strokes
2, connecting rods; 3, pistons; 4, valves;
5, camshafts

Figure 2.3 Diesel and petrol engine: pistons at top dead centre (TDC) before start of the
combustion or power strokes

The next stroke is the compression stroke, when the piston moves upwards in
Key fact the cylinder. Both the inlet and exhaust valves are closed and the space in the
cylinder above the piston is reduced. This causes the air and fuel charge to be
Towards the end of the compression
stroke, the fuel is ignited and burns compressed, which is necessary for clean and effi cient combustion of the fuel.
to give a large pressure rise. Towards the end of the compression stroke, the fuel is ignited and burns to give
a large pressure rise in the cylinder above the piston. This pressure rise forces
the piston down in the cylinder on the combustion or power stroke.