Test: Fuel Injection, Ignition & Carburetor of IC Engine - 2 - Mechanical Engineering MCQ

Combustion in SI engine is homogeneous
Rich mixture is required during idling
Stoichiometric A/F ratio for 1C engine fuels is about 15.

Following are the advantages of multijet carburettors:

• Uniform quality of supply mixture.
• Higher volumetric efficiency.
• Even distribution of charge.
• Compact in its design.

Following additional systems are added:

• Main metering system. 
• idling system.
• Power enrichment by economiser system.
•  Acceleration pump system.
• Choke.
• Throttle valve is common.

An economiser is a valve which remains closed at normal cruise operation and gets opened to supply rich mixture at full throttle operation. It regulates the additional fuel supply during the full throttle operation.

An Si engine sometimes continues to run for a very small even after the ignition is switched off. It is called as dieseiing. Dieseling may take place due to following:

• High engine idling speed.
• Increase in compression ratio due to carbon deposits.
• Engine overheating.
• Too high spark plug heat range,
• Incorrect adjustment of idle fuel-air mixture.
• Sticking of throttle. 
• Requirement of tune up of engine.
• Oil entry into the cylinder.

where z is the height of nozzle exit above the level of fuel in the float bowl.

A precise petrol injection system is direct injection. In direct injection, fuel is injected directly into the combustion chamber of each cylinder, rather than into the intake manifold or throttle body. This allows for more precise fuel metering, better atomization, and more efficient combustion, resulting in improved fuel economy, increased power, and lower emissions. Direct injection allows for more precise control over the fuel-air mixture, enabling the engine management system to optimize performance and efficiency under various operating conditions.