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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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Overcoming Twisting Effects: The correct firing order helps to minimize the twisting effect on the crankshaft caused by the power strokes. This ensures smoother operation and reduces stress on crankshaft components.
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Reducing Vibrations: Adhering to the correct firing order helps reduce vibrations, leading to a more stable engine operation. This is crucial for engine longevity and driver comfort.
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Lifespan and Cooling: Utilizing the proper firing order increases the lifespan of the crankshaft and helps improve engine cooling by evenly distributing the power strokes.
Step 2
State TWO ways in which dynamic imbalance of the crankshaft can be corrected.
Answer
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Adding Balance Masses: Balance masses can be added to the crank webs to counteract any imbalances caused by the arrangement of the crankshaft.
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Vibration Dampers: Installing a vibration damper can help to absorb and counteract dynamic imbalances, promoting smooth operation.
Step 3
State FOUR causes of engine vibration.
Answer
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Mismatch of Torque: Variation in the quantity of torque produced during engine operation can lead to vibrations.
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Improperly Balanced Components: An unbalanced crankshaft or flywheel, either statically or dynamically, can cause excessive vibrations.
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Mechanical Issues: Problems such as engine misfire or worn parts also contribute to engine vibration.
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Incorrect Air/Fuel Mixture: An improper air/fuel ratio may lead to inconsistent combustion, resulting in vibration.
Step 4
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Step 6
Describe the operation of the Roots supercharger.
Answer
The operation of the Roots supercharger involves the engine driving the rotors through a system of gears, belts, or chains. The supercharger consists of two symmetrical rotors that rotate within a casing. As they spin, air trapped between the rotors and the casing is pushed from the intake side to the discharge side, increasing pressure in the cylinder and enhancing engine 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 cools the compressed air from the turbocharger to increase density and improve volumetric efficiency.
6.6.2 Vanes: The vanes adjust the flow of exhaust gases to optimize the turbine speed and efficiency of the turbocharger.
Step 8
State THREE advantages of a supercharger when compared to a turbocharger.
Answer
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Instantaneous Power: Superchargers provide immediate boost from the moment the engine is revved, eliminating turbo lag.
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Simplicity of Installation: They are generally easier to install than turbo systems, which often require complex piping and intercoolers.
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Reliability: Superchargers do not rely on exhaust gases, leading to fewer heat-related issues and potentially lower maintenance requirements.