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Proper balancing of all moving engine parts is essential at a high engine speed - NSC Mechanical Technology Automotive - Question 6 - 2019 - Paper 1
Question 6
Proper balancing of all moving engine parts is essential at a high engine speed. Answer the questions that follow. 6.1.1 State TWO methods to balance the engine cra... show full transcript
Worked Solution & Example Answer:Proper balancing of all moving engine parts is essential at a high engine speed - NSC Mechanical Technology Automotive - Question 6 - 2019 - Paper 1
Step 1
State TWO methods to balance the engine crankshaft.
Answer
The two methods to balance an engine crankshaft are:
- Static Balance: This involves fitting balance mass pieces to the crank webs or removing metal from the crank.
- Dynamic Balance: Vibration is reduced by removing metal from certain parts to form parts of the crank webs.
Step 2
Briefly explain how the balancing is done using EACH of the methods in QUESTION 6.1.1.
Answer
In static balancing, the crankshaft is positioned so that all parts remain in equilibrium and can rotate freely without wobbling. This is checked using a level surface. For dynamic balancing, the crankshaft is rotated at a specific speed, and sensors are used to detect vibrations, allowing for adjustments by removing material from areas with excess weight.
Step 3
State TWO factors that cause vibration in an internal combustion engine.
Answer
Factors that cause vibration in an internal combustion engine include:
- Mechanical Unbalance: This is caused by unbalanced moving parts, leading to vibrations during operation.
- Power Unbalance: It is caused by uneven pressure on the pistons and crankshaft, resulting in inconsistent forces acting throughout the engine cycle.
Step 4
State TWO factors that will determine the firing order in an internal combustion engine.
Answer
Factors that determine the firing order in an internal combustion engine are:
- The position of the cranks on the crankshaft: This influences how the engine fires as it rotates.
- The arrangement of the cams on the camshaft: The camshaft’s setup ensures correct timing in relation to the engine's operation.
Step 5
Explain the function of a vibration damper in an internal combustion engine.
Answer
A vibration damper functions by being mass fitted to the crankshaft on the opposite side of the flywheel to counteract torsional vibrations of the crankshaft. It absorbs oscillations to dampen vibrations, enhancing the engine's smooth operation and prolonging its life.
Step 6
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Step 8
State TWO advantages of a motor vehicle fitted with a supercharger.
Answer
Advantages of a motor vehicle fitted with a supercharger include:
- Increased engine power output, making the vehicle more responsive.
- Enhanced fuel efficiency as the supercharged engine can produce more power per gallon of fuel.
Step 9
Explain how a turbocharger on an internal combustion engine operates.
Answer
A turbocharger operates by routing exhaust gases from the engine to the turbine wheel, which enables the turbine wheel to spin at a very high speed. As exhaust gases exit the engine, they spin the turbine, which in turn drives the compressor wheel, drawing in more air. This compressed air increases the engine’s intake charge, providing more power and efficiency.
Step 10
State TWO disadvantages of turbochargers when compared with superchargers.
Answer
Disadvantages of turbochargers include:
- Lag: Turbochargers may experience a delay in power delivery, commonly known as turbo lag.
- Complexity: Turbo systems require more components and additional cooling, making them harder to maintain compared to superchargers.
Step 11
Explain the effect of high altitude on the performance of an internal combustion engine.
Answer
At high altitudes, the air density decreases, leading to less oxygen available for combustion. Consequently, the engine’s performance is reduced, often causing it to run lean, produce less power, and exhibit a decline in fuel efficiency compared to operation at sea level.