# Automotive Engine Components Design Questions and Answers – IC Engine – Piston Rings

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This set of Automotive Engine Components Design Multiple Choice Questions & Answers (MCQs) focuses on “IC Engine – Piston Rings”.

1. Which are the two types of piston rings in the piston?
a) Bearing and compression rings
b) O-ring and oil rings
c) O-ring and bearing
d) Compression rings and oil rings

Explanation: The compression ring and the oil ring are the two types of piston rings in the piston, whereas bearing is used to bear the load and O-ring doesn’t come into the picture.

2. What is the function of the compression ring?
a) To seal between piston and cams
b) To seal between cylinder and crank
c) To seal between cylinder and piston
d) To seal between crank and cams

Explanation: The main function of the compression ring is to maintain the seal between the cylinder and the piston, also they transfer heat from the piston head to the cylinder wall.

3. What is the function of the oil ring?
a) To allow charge to the crankcase
b) To increase friction
c) To reduce the frictional losses
d) To compress charge

Explanation: Oil ring is also known as Oil scrapper rings placed below compression rings, they provide proper lubrication of the cylinder liner and reduce frictional losses.
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4. Piston rings are usually made of which material?
a) Cast iron
b) Nichrome
c) Tungsten
d) Silver

Explanation: Piston rings are usually made of grey cast iron or in some cases alloy cast iron since it has excellent wear resistant property.

5. Usually how many piston rings are present in a petrol engine?
a) 1
b) 3 to 4
c) 7-10
d) 2

Explanation: There is no restriction for deciding the number of piston rings in the automobile. Usually, petrol engines have 3-4 piston rings and diesel engines have 5-7 piston rings.
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6. The compression rings have which cross-section?
a) Triangular cross-section
b) Circular cross-section
c) Rectangular cross-section
d) Square cross-section

Explanation: The compression rings have rectangular cross-section because rectangular cross-section can withstand more pressure when compared to other cross-sections.

7. In the formula b=D$$\sqrt{\frac{3P_w}{\sigma_t}}$$, what is the unit of Pw?
a) N/mm2
b) N/m
c) KN/mm
d) N/m2

Explanation: Pw is the allowable radial wall pressure on the cylinder wall and pressure is defined as a force upon the unit area. Hence, N/mm2 is the unit.

8. Find the range of axial thickness of the piston ring, when b=7.5mm?
a) 3.5 to 4mm
b) 4.6 to 3mm
c) 5.78 to 8.4mm
d) 5.25 to 7.5mm

Explanation: The axial thickness of the piston ring is given by h=0.7b to b
= 0.7×7.5 to 7.5
= 5.25 to 7.5mm

9. Find the limit on the minimum axial thickness when D=150mm and Z=7?
a) 1.5mm
b) 3.7mm
c) 2.14mm
d) 4.87mm

Explanation: hmin=$$(\frac{D}{10Z})$$
= 150/(10×70)
= 2.14mm

10. Find the Radial width of the piston ring, when D=250mm, σt=100MPa, and pw=0.03N/mm2?
a) 5.5mm
b) 7.5mm
c) 4.5mm
d) 6.5mm

Explanation: b=D$$\sqrt{\frac{3P_w}{\sigma_t}}$$
= 150$$\sqrt{\frac{3×0.03}{100}}$$
= 7.5mm

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