Theory of Engine Operation - Delmar Learning

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Terms to Know Kinetic energy Mechanical efficiency Net horsepower Overhead valve (OHV) Piston rings Potential energy Preignition Reciprocating Reed valve Rotary valve Solenoid Spark-ignition (SI) engine Stroke Thermal efficiency Thermodynamics Top dead center (TDC) Torque Transverse-mounted engine Valve overlap Variable valve timing (VVT) systems Volumetric efficiency (VE) Wrist pin Review Questions Short Answer Essays 1. Describe how the basic laws of thermodynamics are used to operate the automotive engine. 2. List and describe the four strokes of the four-stroke-cycle engine. 3. Describe the different cylinder arrangements and the advantages of each. 4. Describe the different valvetrains used in modern engines. 5. Describe the basic operation of the stratified charge engine. 6. Define the term cycle. 7. Define the term stroke. 8. Explain how the air-fuel mixture is ingested into the cylinder. 9. Explain the basic operation of the two-stroke engine. 10. Describe the basic operation of the Miller-cycle engine. Fill-in-the-Blanks 1. Most automotive and truck engines are ____________________ cycle engines. 2. During the intake stroke, the intake valve is ____________________, while the exhaust valve is __________________ _ . 3. The __________________ _ engine places all of the cylinders in a single row. 4. An __________________ _ __________________ _ engine has the valve mechanisms in the cylinder head, while the camshaft is located in the engine block. 5. A __________________ _ is a sequence that is repeated. 6. In a four-stroke engine, four strokes are required to complete one ____________________ . 7. Instead of using a spark produced by the ignition system, the diesel engine uses the ____________________ produced by compressing air in the combustion chamber to ignite the fuel. 8. A __________________ _ __________________ _ engine has a power stroke every revolution. 9. In a two-cycle engine the air-fuel mixture enters the crankcase through a __________________ _ __________________ _ or __________________ _ __________________ _ . 10. The __________________ _ __________________ _ engine uses combustion from the precombustion chamber to ignite the air-fuel mixture in the main combustion chamber. 46
Multiple Choice 1. Increasing the compression ratio of an engine is being discussed. Technician A says increased compression ratios result in a reduction of power produced. Technician B says higher compression ratio engines require higher octane gasoline. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 2. Engine measurement is being discussed. Technician A says the bore is the distance the piston moves within the cylinder. Technician B says the stroke is the diameter of the cylinder. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 3. Technician A says to determine horsepower, torque must be known first. Technician B says horsepower will usually peak at a lower engine speed than torque. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 4. Technician A says mechanical efficiency is a comparison between brake horsepower and indicated horsepower. Technician B says volumetric efficiency is a measurement of the amount of air-fuel mixture that actually enters the combustion chamber compared to the amount that could be drawn in. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 5. During the compression stroke in a four-cycle engine: A. The intake valve is open, and the exhaust valve is closed. B. The exhaust valve is open, and the intake valve is closed. C. Both valves are open. D. Both valves are closed. 6. All of these statements about diesel engines are true EXCEPT: A. The air-fuel mixture is ignited by the heat of compression. B. Glow plugs may be used to heat the air-fuel mixture during cold starting. C. Spark plugs are located in each combustion chamber. D. Diesel engines may be two-cycle or four-cycle. 7. While discussing volumetric efficiency: Technician A says volumetric efficiency is not affected by intake manifold design. Technician B says volumetric efficiency decreases at high engine speeds. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 8. In a two-stroke cycle engine: A. A power stroke is produced every crankshaft revolution. B. Intake and exhaust valves are located in the cylinder head. C. The lubricating oil is usually contained in the crankcase. D. The crankcase is not pressurized. 9. In an engine with a balance shaft: A. The balance shaft does not have to be timed to the crankshaft. B. The balance shaft turns at twice the crankshaft speed. C. The balance shaft may be mounted on the cylinder head. D. The balance shaft increases engine torque. 10. While discussing engine identification: Technician A says that the tenth character of the VIN defines the vehicle model year. Technician B says that an engine identification tag may identify the date on which the engine was built. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 47
Page 1 and 2: Theory of Engine Operation Upon com
Page 3 and 4: Figure 2-2 This engine cutaway show
Page 5 and 6: Figure 2-6 A camshaft. belt, and is
Page 7 and 8: energy exerted on top of the piston
Page 9 and 10: molecules become less dense and the
Page 11 and 12: Engine Classifications Engine class
Page 13 and 14: Exhaust camshaft 2. Overhead cam (O
Page 15 and 16: second vibration occurs when all pi
Page 17 and 18: Plug Engine Displacement Retainer F
Page 19 and 20: Most engine manufacturers designate
Page 21 and 22: transmits this torque to the drivet
Page 23 and 24: Torque output @ 3,500 rpm 5 115 lb.
Page 25 and 26: Transfer port Most gasoline two-str
Page 27 and 28: Intake valve rich mixture Precombus
Page 29 and 30: Figure 2-33 The VIN number can be s
Page 31: Figure 2-37 Additional markings ind

Theory of Engine Operation - Delmar Learning

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