Question

The pressure at the end of compression in the case of diesel engine is of the order of
1. 35 kg/cm²
2. 6 kg/cm²
3. 12 kg/cm²
4. 20 kg/cm²

Answer 1

Correct Answer - Option 1 : 35 kg/cm²

Explanation:

SI engine	CI engine
Petrol is used as fuel.	Diesel is used as fuel.
A petrol engine draws a mixture of petrol and air during the suction stroke.	A diesel engine draws only air during the suction stroke.
The pressure at the end of the compression is about 10 kg/cm2.	The pressure at the end of the compression is about 35 kg/cm2.
The charge (i.e. petrol and air mixture) is ignited with the help of spark plug.	The fuel is injected in the form of a fine spray. The temperature of the compressed air is about 600° C at a pressure of about 35 bars.
A  carburettor is used to atomize, vaporize and meter the correct amount of fuel according to the requirement.	Fuel injection pumps and atomizers are used to inject metered quantities of fuel at high pressure according to the requirement.
A petrol engine has a compression ratio approximately from 6 to 10.	A diesel engine has a compression ratio of approximately 15 to 25.
The combustion of fuel takes place approximately at a constant volume. In other words, it works on the Otto cycle.	The combustion of fuel takes place approximately at constant pressure. in other words, it works on the Diesel cycle.
Less vibration, and hence, smooth running.	More vibration, and hence, rough running and noisier.
Engine weight is less.	Engine weight is more.
It emits carbon monoxide. (CO)	It emits carbon dioxide. (CO2)