Internal Combustion Engines (I.C. Engines) MCQ Questions & Answers | Mechanical Engineering

Diesel engine can work on very lean air fuel ratio of the order of 30 : 1. A petrol engine can also work on such a lean ratio provided cannot work as it is impossible.
- For cold starting (simply when your engine parts are not warmed) - 9 : 1 (rich of fuel)
- For Idling (when you stop at signal without turning off engine) - 12 : 1 (rich mixture)
- For cruising (when you run engine at constant medium/economy speed) - 16 : 1 (lean mixture)
- When you accelerate bike/car - 13 : 1 (rich mixture but require less fuel than idling)

cc stands for cubic centimeters, a unit of volume. This number basically is approximately the displacement volume of the engine i.e. the volume covered by the stroke of the piston multiplied by the number of cylinders the engine has.

Diesel is in principle easier to refine than gasoline, however it contains more pollutants that must be extracted before it can reach the same levels of emissions as petrol. Per litre, diesel contains more energy than petrol and the vehicle’s engine combustion process is more efficient, adding up to higher fuel efficiency and lower CO₂ emissions when using diesel.

Diesel as compared to petrol is More difficult to ignite

Fuel consumption of diesel engines is not guaranteed at one quarter load because at such low loads The small difference in cooling water temperature or in internal friction has a disproportionate effect

-In compression ignition engines, detonation occurs near the beginning of combustion.
-Since the fuel, in compression ignition engines, is injected at the end of compression stroke, therefore, there will be no pre-ignition.
-In compression ignition engines, because of heterogeneous mixture, the rate of pressure rise is comparatively lower.

- Typically, a 2-stroke engine creates more torque at a higher RPM, while a 4-stroke engine creates a higher torque at a lower RPM.
- The petrol engines are cheaper than diesel engines.

The magneto in an automobile is basically D.C. generator. A magneto is an electrical generator that uses permanent magnets to produce periodic pulses of alternating current. Unlike a dynamo, a magneto does not contain a commutator to produce direct current. It is categorized as a form of alternator, although it is usually considered distinct from most other alternators, which use field coils rather than permanent magnets.

The purpose of testing an internal combustion engine is:
- To determine the information, which cannot be obtained by calculations
- To conform the data used in design, the validity of which may be doubtful
- To satisfy the customer regarding the performance of the engine

The knocking in spark ignition engines can be reduced by - Retarding the spark -Increasing the engine speed