Questions and Answers
In an overhead cam engine, the camshaft is located in the
cylinder head
The vast majority of automobile engines operate on the
four-stroke cycle
This part has carefully machined high spots called lobes.
Camshaft
A fuel cell electric vehicle
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Piston rings are used to
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This type of engine relies on the heat of compression to ignite the fuel.
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Exhaust valves are __________ than intake valves.
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This type of engine delivers power with every downstroke of the piston.
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During this mode, an electric vehicle's motor is driven by the wheels, becoming a generator to charge the batteries.
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Production of this type of engine was discontinued in 1995 and re-introduced in 2003.
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The volume of the cylinder, including the combustion chamber, with the piston at BDC compared to the volume at TDC is known as the
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Ignition systems that use a distributor to send a spark on its way to each cylinder are referred to as
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At higher RPM, the spark timing must be
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Torque is generally greatest at _________ RPM, while horsepower is generally greatest at ________ RPM.
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A V-type DOHC engine has ________ camshafts.
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Spark knock is ________________ than pre-ignition.
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In a pushrod engine, the camshaft is located in the
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This condition occurs when the air-fuel mixture self-ignites during the compression stroke before the spark plug fires.
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Technician A says that higher compression engines require a lower octane fuel to prevent spark knock. Technician B says that carbon deposits in the combustion chamber can cause spark knock or pre-ignition. Who is correct?
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This condition is caused when the flame front initiated by the spark plug collides with an undesired flame front.
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Technician A says that the optimum operating temperature for an engine is around 140 degrees F. Technician B says that cooling system pressure is typically regulated to about 15 psi. Who is correct?
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Technician A says that worn main bearings will cause low oil pressure at the valve train. Technician B says that a clogged oil filter will cause oil starvation on most engines. Who is correct?
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Technician A says that a catalytic converter changes HC, CO, and NOx into H2O, CO2, and N. Technician B says that the PCV system removes blow-by gases from the crankcase and routes them to the exhaust system. Who is correct?
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Technician A says that the emissions that are regulated are HC, O2, and NOx. Technician B says that the EGR valve opens at idle to reduce NOx. Who is correct?
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Technician A says that some EI ignition systems use a pickup coil in the distributor to send a trigger signal to the control module. Technician B says that on waste spark systems, pairs of spark plugs that share a coil fire one after the other. Who is correct?
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Technician A says that different manufacturers use different terminology in the OBD terms for their OBDII compliant vehicles. Technician B says that PCM digital output signals may be modulated by pulse width or frequency. Who is correct?
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Technician A says that in an ignition system, the coil is part of both the primary and secondary circuits. Technician B says the switching device is part of the secondary circuit. Who is correct?
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Technician A says the intake manifold on an MFI system carries both air and fuel. Technician B says that engine RPM determines when an injector opens. Who is correct?
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Study Notes
Engine Components and Functions
- In overhead cam engines, the camshaft is positioned in the cylinder head, optimizing valve timing.
- Most automobile engines operate on the four-stroke cycle, consisting of intake, compression, power, and exhaust strokes.
- The camshaft features lobes, which are precisely machined high spots that control valve movement.
- Piston rings seal the combustion chamber, control oil consumption, and improve engine efficiency.
- Spark knock occurs when combustion pressure increases prematurely, while pre-ignition is when the air-fuel mixture ignites before the spark plug fires.
Types of Engines
- Diesel engines ignite fuel using heat generated from compression rather than a spark plug.
- A two-stroke cycle engine produces power on every downstroke, offering higher power-to-weight ratios.
- Rotary engines were discontinued in 1995 and reintroduced in 2003, known for their unique design and operation efficiencies.
Electric and Hybrid Systems
- Fuel cell electric vehicles utilize hydrogen as fuel and oxygen from the atmosphere, providing an emissions-free driving experience.
- Regenerative braking allows an electric vehicle's motor to act as a generator, recharging the batteries during braking.
Engine Performance and Measurements
- The compression ratio compares the cylinder volume at Bottom Dead Center (BDC) to that at Top Dead Center (TDC), critical for engine efficiency.
- Torque is maximized at lower RPMs, while horsepower peaks at higher RPMs, reflecting different facets of engine performance.
- Spark timing must be advanced at higher revolutions per minute (RPM) for optimal performance under load conditions.
Technician Insights and Facts
- Technicians vary in their understanding of engine systems: Technician A noted the optimum engine temperature around 140°F, while Technician B correctly stated cooling system pressure is approximately 15 psi.
- Worn main bearings can lead to low oil pressure; oil starvation may occur due to a clogged filter, emphasizing regular maintenance.
- Technicians are misinformed about emissions; regulated emissions include HC, O2, and NOx, but the EGR valve's function is misunderstood regarding idle operation.
- OBD II terminology varies by manufacturer, and PCM digital output signals can be modulated through pulse width or frequency.
Ignition Systems
- Electronic ignition (EI) systems often incorporate a pickup coil in the distributor for spark timing.
- On waste spark ignition systems, pairs of spark plugs share a single ignition coil, but they do not fire sequentially as sometimes misunderstood.
Fuel Injection Systems
- Multi-Point Fuel Injection (MFI) systems utilize intake manifolds that carry both air and fuel; the timing of injector openings is influenced by engine RPM, ensuring accurate fuel delivery.
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Description
Test your knowledge of automotive engineering concepts with these flashcards. From camshaft locations to fuel cell electric vehicles, this quiz covers essential terms and definitions related to engine operations. Perfect for students and enthusiasts alike.
