1 Four-stroke SI Engine
The valve timing diagram shows the regulation of the positions in the cycle at which the valves are set to open and close. The valve timing diagrams for low and high speed four-stroke S.I. engine are shown in Fig. 10.9. Typical valve timings are given in Table 10.3.
2 Four-stroke CI Engine
A typical valve timing diagram for a four-stroke CI engine is shown in Fig. 10.10. The typical timing valves are also displayed.
IVO up to 30° before TDC; IVC up to 40° after BDC
EVO about 45° before BDC; EVC about 30° after TDC
Fuel valve opens (FVO) about 15° before TDC; FVC about 25° after TDC.
3 Two-stroke SI Engine
The transfer port opens 35° before the BDC and closes 35° after the BDC. The exhaust port opens 45° before the BDC and closes 45° after the BDC. The spark ignition occurs 20° before the TDC. The typical valve timing diagram for two-stroke engine is shown in Fig. 10.11.
Figure 10.9 Valve timing for low and high speed four-stroke SI engine: (a) Low speed engines, (b) High speed engines
Table 10.3 Typical valve timings for four-stroke SI engines
Figure 10.10 Valve timing diagram four-stroke CI engine
Figure 10.11 Typical valve timing diagram of a two-stroke SI engine
4 Two-stroke CI Engine
The transfer port opens 45° before the BDC and closes 45° after the BDC. The exhaust port opens 60° before the BDC and closes 60° after the BDC. The fuel valve opens 15° before the TDC and closes 20° after the TDC. The typical valve timing diagram is shown in Fig. 10.12.
Figure 10.12 Valve timing diagram for a two-stroke CI engine
Leave a Reply