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As the maximum power range of operation (75% to 100% load) is approached, some device must allow richer mixture (A/F about 13: 1, F/A 0.08) to be supplied despite the compensating jet. Such a device is the meter rod economiser shown in Fig. 10.31. The name economiser is rather misleading. It stems from the fact that…

It has already been shown that at idling and low lead, the engine requires a rich mixture (about A/F 12:1). However, the main metering system not only fails to enrich the mixture at low air flows but also supplies no fuel at all at idling. For this reason, a separate idling jet must be added…

The main metering system of a carburettor is designed to supply a nearly constant basis fuel-air ratio over a wide range of speeds and loads. This mixture corresponds approximately to best economy at full throttle (A/F ratio ≈ 15.6 or F/A ratio 0.064). Since a simple or elementary carburettor tends to enrich the mixture at…

In SI engines, the air and fuel are mixed outside the engine cylinder and partly evaporated mixture is supplied to the engine. The process of preparing this mixture is called carburetion. The device used for this purpose is known as carburettor. The carburettor atomises the fuel and mixes it with air. This complicated process is achieved in the…

1 Four-stroke Petrol Engine The theoretical and actual p-v diagrams for a four-stroke petrol engine are shown in Figs. 10.16(a) and (b), respectively. The theoretical p–v diagram is drawn with the following assumptions: The various processes of theoretical p-v diagram are as follows: 5-1: Suction stroke (pa = const) 1-2: Compression stroke (pvγ = const) Figure 10.16 Theoretical and actual p-v diagrams for a four-stroke petrol engine: (a)…

The detail applications with capacity and type of engine used are listed in Table 10.4.   Table 10.4 Applications of IC engines  

At the end of the expansion stroke, the combustion chamber of a two-stroke engine is left full of products of combustion as there is no exhaust stroke available to clear the cylinder of burnt gases. The process of clearing the cylinder, after the expansion stroke, is called scavenging process. The scavenging process is the replacement…

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…

1 Merits 2 Demerits

Table 10.2 gives the comparison of SI and CI engines.   Table 10.2 Comparison of SI and CI engines