# Farm Tractor Questions and Answers – Engine Design

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

1. Which engine has lengthier stroke than bore?
a) Long-stroke engine
b) Long bore engine
c) Lengthy engine
d) Square engine

Explanation: This type of engine has a smaller bore and with higher stroke length. It is also called as under square engine and so it has bore – stroke ratio lesser than 1:1. It has increased friction and higher brake specific fuel consumption. Tractor engines are mostly built with this kind of engines for better torque generation.

2. Top dead centre is the farthest point away from the crankshaft.
a) False
b) True

Explanation: Top dead centre (TDC) is the point which is the end for piston motion. The reciprocating piston has two dead extents and TDC is the top in vertical cylinder engines. In horizontal cylinder engines, it is the inner dead centre (IDC).

3. What is the total volume of the cylinder?
a) Swept volume – clearance volume
b) Clearance volume – swept volume
c) Swept volume + clearance volume
d) Top dead centre + clearance volume

Explanation: The total volume of the cylinder is the sum of the volume of the swept and clearance volume. The clearance volume is the volume when the piston is at the TDC. It is the space for mixing of air and fuel in a diesel engine.

4. What is swept volume?
a) Volume between TDC and BDC
b) TDC – BDC
c)Total volume – BDC
d) Total volume – TDC

Explanation: Swept volume is the volume between two dead centres through which the piston can move. It is also called as displacement volume. It can be calculated using the formula (swept volume) Vs = A * L = πd2/4 * (stroke length); Where A is the area, L is the stroke length and d is the bore diameter of the cylinder.

5. What is known as the ratio of total volume to the clearance volume?
a) Expansion ratio
b) Compression ratio
c) Volume ratio
d) Clearance ratio

Explanation: The compression ratio is the ratio of the total volume of the cylinder to the clearance volume of the cylinder. It can vary for diesel and petrol engines. The compression ratio of a diesel engine is higher due to self-ignition of fuel without external source and in the range of 14:1 to 20:1.

6. What is the speed of the piston?
a) 2LN
b) LN
c) L+N
d) L-N

Explanation: The speed of the piston is 2 * L * N, where L is the length of the stroke and N is the rpm (revolution per minute) of an engine. The two in the equation represents two strokes for a single revolution (360°) of the crankshaft. It is the average speed of the piston and so often called as mean piston speed.

7. What is valve timing?
a) Opening of inlet valve
b) Opening and closing of both valves
c) Closing of outlet valve
d) Opening of outlet valve

Explanation: The valve timing represents the opening and closing of both the inlet and outlet valves of an engine. The valves are poppet valves. There will be a timing gear in tractors for controlling the opening and closure of valves.

8. The bottom dead centre is the nearest point to the crankshaft.
a) True
b) False

Explanation: The bottom dead centre (BDC) is the lowest point of piston motion when it is sliding downwards. It is the outer dead centre (ODC) in horizontal cylinder engines. There is no turning force generation in the crankshaft at dead centre positions.

9. What is a square engine?
a) Smaller bore
b) Stroke length and bore are equal
c) Longer stroke
d) Stroke length and bore are unequal

Explanation: The stroke length and bore diameter of the cylinder are equal in measure. As they are equal, the bore – stroke ratio will be 1:1. Bore – stroke ratio is the ratio of bore diameter to the stroke length. There is also another term stroke – bore ratio, which is vice versa to the former.

10. Which of the following engine has higher bore?
a) Over square engine
b) Under square engine
c) Long-stroke engine
d) Square engine

Explanation: The bore diameter is higher than the stroke length, it is known as the over square engine. It is also called a short-stroke engine. It has a bore – stroke ratio greater than 1:1. This type of engine develops higher engine rpm relatively to other engines.

11. What is a valve timing diagram?
a) Diagram of inlet valve
b) Graphical representation of valve timings
c) Diagram of outlet valve
d) Diagram of rocker arm

Explanation: Valve timing diagram is a representation of valve timings i.e. opening and closing of inlet, outlet valves of an engine. The theoretical diagram represents the valve timings with perfect opening and closing according to the starting and ending of strokes theoretically. But the actual diagram represents the actual process where the inlet valve begins to open before the suction stroke and actual operation time varies for all the valves in the practical process.

12. What is the firing order?
a) Order of firing
b) Order of strokes
c) Order of valve closing
d) Order of valve opening

Explanation: The firing order is the sequence of power stroke or ignition in each cylinder of an engine. Because there will be variation in power strokes occurrence in multiple cylinder engine. The arrangement of crankpin in the crankshaft and also the camshaft determines the firing order. The firing order for a four-cylinder engine will be 1-3-4-2.

Sanfoundry Global Education & Learning Series – Farm Tractor.

To practice all areas of Farm Tractor, here is complete set of Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]