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6.1 With reference to the crankshaft, give THREE reasons for using the correct firing order on an internal combustion engine - NSC Mechanical Technology Automotive - Question 6 - 2021 - Paper 1
Question 6
6.1 With reference to the crankshaft, give THREE reasons for using the correct firing order on an internal combustion engine. 6.2 State TWO ways in which dynamic im... show full transcript
Worked Solution & Example Answer:6.1 With reference to the crankshaft, give THREE reasons for using the correct firing order on an internal combustion engine - NSC Mechanical Technology Automotive - Question 6 - 2021 - Paper 1
Step 1
With reference to the crankshaft, give THREE reasons for using the correct firing order on an internal combustion engine.
Answer
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Twisting Effect: The correct firing order helps to overcome the twisting effect of the power stroke on the crankshaft, ensuring smooth operation and reducing stress on the components.
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Vibration Reduction: Adhering to the proper firing order minimizes vibrations transmitted through the crankshaft, leading to improved comfort and stability in the engine assembly.
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Engine Cooling: It promotes even engine cooling by distributing the workload evenly, which enhances the longevity and performance of the engine.
Step 2
State TWO ways in which dynamic imbalance of the crankshaft can be corrected.
Answer
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Adding Balance Masses: Fit balance mass pieces to the crank webs to counteract dynamic imbalances that can cause excessive vibrations.
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Vibration Dampers: Incorporate a vibration damper to absorb oscillations and stabilize the crankshaft during operation.
Step 3
State FOUR causes of engine vibration.
Answer
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Torque Variation: The varying quantity of torque produced on power strokes can cause vibrations.
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Imbalance in Components: Components such as the crankshaft or flywheel that are not statically or dynamically balanced can lead to vibrations during operation.
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Engine Misfire: An engine misfire disrupts the normal firing order, creating irregular vibrations.
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Worn Parts: Components that are worn can lead to loss of balance and, consequently, vibrations.
Step 4
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Step 6
Describe the operation of the Roots supercharger.
Answer
The Roots supercharger operates by using two symmetrical rotors that spin. As the engine drives the rotors by means of gears, belt, or a chain, air is trapped between the rotors and the casing. This air is then pushed from the inlet side to the discharge side, creating increased pressure in the cylinder, which enhances the engine’s performance.
Step 7
What is the function of the following components on an internal combustion engine equipped with a variable geometry turbocharger:
Answer
6.6.1 Intercooler: The intercooler is designed to cool air that has been compressed by the turbocharger, reducing the volume and increasing the density of the air, thus improving volumetric efficiency.
6.6.2 Vanes: The vanes adjust the exhaust gas flow to optimize the turbine speed, allowing for better performance across a range of engine speeds.
Step 8
State THREE advantages of a supercharger when compared to a turbocharger.
Answer
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Immediate Power Delivery: Superchargers provide quicker power delivery as they are mechanically driven by the engine rather than relying on exhaust gases, resulting in less lag.
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Simpler Installation: Superchargers are generally easier and simpler to install than turbochargers, often requiring fewer modifications to the engine setup.
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No Special Lubrication Needs: Unlike turbochargers that may require specific lubrication systems, superchargers do not have special lubrication requirements, making them simpler to maintain.