Farm Tractor Questions and Answers – Engine Functions

This set of Farm Tractor Multiple Choice Questions & Answers (MCQs) focuses on “Engine Functions”.

1. Power stroke produces the power of the engine.
a) False
b) True

Explanation: The power stroke is the only power producing stroke of the engine. It is the third stroke in the process. The piston moves downward due to the force generated by the combustion of fuel from top dead centre (TDC) to bottom dead centre (BDC). It is also called as expansion or working stroke. Both inlet and exhaust valves are kept closed.

2. In which stroke air intake occurs?
a) Power stoke
b) Expansion stroke
c) Suction stroke
d) Exhaust stroke

Explanation: Suction stroke is the first stroke of the process. Due to pressure difference, the air is pushed into the cylinder. The piston moves from top dead centre (TDC) to bottom dead centre (BDC). The inlet valve gets opened and the exhaust valve remains closed.

3. What happens in compression stroke?
a) Compression
b) Expelling of gases
c) Expansion
d) Exhaustion

Explanation: In compression stroke, both valves remain closed. The charge gets compressed in petrol engines and air only gets compressed in diesel engines. The compression occurs due to the movement of the piston from bottom dead centre (BDC) to top dead centre (TDC).

4. Which stroke is the last sequential stroke?
a) Exhaust stroke
b) Expansion stroke
c) Power stroke
d) Induction stroke

Explanation: The exhaust stroke is the final process and the exhaust valve gets opened, but the inlet valve remains closed. The piston moves from bottom dead centre (BDC) to top dead centre (TDC).The piston movement expels the burnt gases from the cylinder.

5. What is valve overlap?
a) Both valves are opened during engine operation
b) Both valves are closed during engine operation
c) Inlet valve closed in the first stroke of engine operation
d) Inlet valve closed in the last stroke of engine operation

Explanation: At the time of exhaust stroke, the exhaust valve opens before piston reaching BDC. The inlet valve gets opened for the next stroke, i.e. both the valves remain open. This is called as valve overlap.

6. Two-stroke engine produces one revolution in two strokes.
a) True
b) False

Explanation: The two-stroke engine has inlet and outlet ports only. The upward movement of piston performs suction and compression stroke simultaneously. After combustion, the piston moves downward due to power from power stroke and simultaneously the exhaust gases are expelled.

7. What is known as the leakage of gases into the crankcase through piston sides?
a) Ring blow down
b) Ring blow-by
c) Blow out
d) Gas leakage

Explanation: The higher compression pressure makes the combustible gases leak into the oil sump through the gap on the side of the piston. This will occur in most of the engines as there is wear. It will also contaminate the oil in the sump.

8. What is the piston displacement for a single-cylinder engine with a stroke 10 cm and bore 8 cm?
a) 501.55 cm3
b) 502.65 cm3
c) 502.10 cm3
d) 503.50 cm3

Explanation: Piston displacement = A * L
= π/4 * D2 * L
= π/4 * 82 * 10
= 502.65 cm3

9. Find piston speed of an engine with stroke 12 cm, bore 10 cm and rpm 2500.
a) 20 m/s
b) 12 m/s
c) 15 m/s
d) 10 m/s

Explanation: Piston speed = 2LN
= 2 * 12 * 2500
= 60000 cm/min = 600 m/min
= 10 m/s

10. What is the firing interval?
a) Interval between firing
b) Interval between exhaust strokes
c) Interval between suction strokes
d) Interval between compression strokes

Explanation: Firing interval is the interval time between the two successive power strokes in an engine. The firing interval for a four-stroke engine can be calculated by FI = 720°/n where n – number of cylinders. In the two-stroke engine, it has one power stroke in a single revolution and Firing interval will be FI = 360°/n.

Sanfoundry Global Education & Learning Series – Farm Tractor.

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