This set of Automotive Engine Auxiliary Systems Multiple Choice Questions & Answers (MCQs) focuses on “Engine Components – Piston Rings”.
1. Which among the following is not a function of the piston rings?
a) To seal the high-pressure gases
b) Easy passage for the heat to flow from crown to cylinder
c) Maintain sufficient lubrication
d) Helps in detonation
View Answer
Explanation: The piston ring should seal for the high-pressure gases from the combustion chamber, should provide easy passage for heat flow from the piston to the crown,should maintain sufficient lubricating oil on cylinder walls throughout and should not help is detonation.
2. Which of the following is provided to make up for the cylinder wear?
a) Ring expander
b) Temperature sensor
c) Pressure relief valve
d) Crankcase ventilation
View Answer
Explanation: The primary purpose of a ring expander it to make up for the cylinder wear which happens after some time. This cylinder wear has to avoided or else it may lead to many wear like scuffing, rapid wear, and ring breakage as well.
3. Which among the following is defined as percentage gap collapse when the ring closed to nominal cylinder diameter for 6 hrs at 350 degrees centigrade?
a) Thermal set
b) Pulse width
c) Base pulse width
d) Enthalpy
View Answer
Explanation: The thermal set is defined ad the percentage gap collapses when the ring closed to nominal cylinder diameter for 6 hours at 350 degrees centigrade. The value thermal set for U1 is 12.5 it depends on the material used and the method used for casting.
4. Which of the following is not a factor for scuffing?
a) Proper protecting lubrication film
b) Overheated engine
c) Insufficient clearance
d) Lack of lubrication
View Answer
Explanation: The main cause for scuffing is overheatedengine, lack of lubrication, insufficient clearance. An overheated engine wherein there is no proper cooling system and leakage of coolant. When a protective lubricating oil film is provided no scuffing takes place.
5. Which among the following type of piston ring is used for worn-out cylinders?
a) Delay action scraper ring
b) Composite rail scraper ring
c) Multi-piece oil control ring
d) Carbo glide ring
View Answer
Explanation: The composite rail scraper ring is highly useful for worn-out cylinders having ovality or taper in the bores. Several steel rails are chrome plated and have rounded ends provide a smooth scraping action reducing wear of cylinder wall.
6. Which of the is caused due to excess of end gap?
a) Blow by and rapid wear
b) Scuffing and rapid wear
c) only rapid wear
d) Both blow bye and scuffing
View Answer
Explanation: The amount of end gap has to be determined cautiously. Excessive end gap would result in blow-by and scuffing of the ring. On the other hand,the lesser the clearance would cause the ring ends to butt at high temperature resulting in non-uniform pressure.
7. Which of the following is not an advantage of reducing the ring width?
a) Machining the narrow grooves
b) Better resistance to ring scuffing
c) better resistance to ring flutter
d) Ring inertia are reduced
View Answer
Explanation: The advantages of having a reduced ring width are better resistance to scuffing, better resistance to ring flutter, problems on ring inertia are reduced, lower piston height, and consequently lower engine height and the disadvantage is machining the narrow grooves I’m the piston accurately is quite difficult.
8. What is the range in millimeter of the end gap for the top compression ring per 25mm of bore size?
a) 0.01-0.04
b) 0.04-0.07
c) 0.07-0.12
d) 0.12-0.15
View Answer
Explanation: The end gap for the top compression ring is controlled from 0.07 to 0.12 millimeters per 25 mm of bore size. The second end gap should be 0.12-0.25mm wider than the top ring gap to prevent the gas buildup.
9. Which of the following type of piston ring end gap is shown below?
a) Seal cut
b) Butt
c) Tapered
d) Gapless
View Answer
Explanation: The ring end gaps may be either straight butt type or tapered or seal cut type. The above figure is a tapered type of piston ring. Whereas the tapered and the seal-cut type are more effective in preventing leakage, but are more costly.
10. What is the reduction of gas leakage in a gapless type ring?
a) 40-50
b) 10-20
c) 50-60
d) Has no effect
View Answer
Explanation: Total seal of USA manufactures a gapless rings which though costlier, is claimed to reduce gas leakage by 10 to 20 percent when compared to a conventional ring. The ring gaps are different types depending on their cheapness.
11. Which are the other materials added to cast iron in the manufacturing of piston ring?
a) Aluminum and phosphorus
b) Silicon and aluminum
c) Silicon and manganese
d) Cadmium and phosphorus
View Answer
Explanation: The material that is generally used for the piston ring is fine-grained alloy cast iron containing silicon and manganese. It has good heat and wear-resisting qualities. There are two types of iron alloy in use they are gray cast iron and ductile iron.
12. What is the minimum number of compression rings required in an engine?
a) 5
b) 1
c) 2
d) 3
View Answer
Explanation: A minimum of two compression rings are required because of the high-pressure difference between the combustion chamber and the crankcase at the beginning of the power stroke. This difference may be as high as 70 atmospheres.
13. Which of the following is not a factor for ring selection?
a) Scavenging ratio
b) Dimensions of engine block
c) Piston design
d) Piston displacement
View Answer
Explanation: The various factors necessary to select a ring for an engine are dimensions of the engine block, piston design, piston displacement, piston speed, bore to stroke ratio, cooling capacity, crankcase pressure whereas scavenging ratio has no main role in piston ring selection.
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