Auto Repair Technician Lesson
When the bore is larger than the stroke, the engine is _____.
a.) even.
b.) oversquared.
c.) free wheeling.
d.) undersquared. - ANSoversquared - The space between the piston and the cylinder head when the
piston is at TDC is the clearance space. It's sometimes called the compression or combustion space. The
volume of this space is known as the clearance volume. When the bore is larger than the stroke, the
engine is oversquared, and most of its power is dependent upon revolutions per minute (rpm) and
generated at higher rpm values. When the stroke is larger than the bore, the engine is undersquared,
with most of its power dependent upon torque.
Which stroke of the four-stroke cycle is shown in the above figure?
a.) Intake
b.) Exhaust
c.) Compression
d.) Power - ANSExhaust - Stage 1: During the intake stage, air that has been mixed with fuel is drawn
into the cylinder.
Stage 2: During the compression stage, the piston rises and compresses the air-and-fuel mixture that's
trapped in the combustion chamber.
Stage 3: During the power stage, the air-and-fuel mixture is ignited by a spark, and the contained
explosion of the fuel presses the piston back down in the cylinder. The downward motion of the piston
is transferred to the rod and crankshaft.
Stage 4: During the exhaust stage, the burned exhaust gases are released from the cylinder. During the
exhaust stroke, the piston rises and the exhaust valve opens. The rising piston pushes the remaining
burned gases in the cylinder out through the open exhaust valve.
Technician A says that horsepower is defined as work per unit of time or the rate of doing work.
Technician B says that one horsepower equals 550 foot-pounds per seconds. Who is right?
a.) B only
, b.) Both A and B
c.) Neither A nor B
d.) A only - ANSBoth A and B - Horsepower is defined as work per unit of time. It's the rate of doing work
or torque and is the unit of measurement that expresses the power output of an internal combustion
engine.
1 horsepower = 550 foot-pounds per second
1 horsepower = 33,000 foot-pounds per minute
During which stage of engine operation does the burning mixture of air and fuel force the piston
downward?
a.) Intake
b.) Power
c.) Compression
d.) Exhaust - ANSPower - During the power stroke, when the piston reaches top dead center, the spark
plug fires and ignites the air-and-fuel mixture. The force created by the exploding fuel gases pushes the
piston down in the cylinder.
The small space above the piston in which fuel is burned is called the _____.
a.) top dead center.
b.) crankshaft.
c.) combustion chamber.
d.) cylinder head. - ANScombustion chamber - When the piston is positioned at the very top of the
cylinder, a small amount of open space is still left between the top of the piston and the cylinder head.
This small, open space above the piston is called the combustion chamber. In the combustion chamber,
a mixture of air and gasoline is burned to produce power.
Technician A says that a ratio is a comparison between to values. Technician B says that in a
compression ratio, the main values are the cylinder volumes at the two different piston positions, BDC
and TDC. Who is right?
a.) Both A and B
b.) A only
When the bore is larger than the stroke, the engine is _____.
a.) even.
b.) oversquared.
c.) free wheeling.
d.) undersquared. - ANSoversquared - The space between the piston and the cylinder head when the
piston is at TDC is the clearance space. It's sometimes called the compression or combustion space. The
volume of this space is known as the clearance volume. When the bore is larger than the stroke, the
engine is oversquared, and most of its power is dependent upon revolutions per minute (rpm) and
generated at higher rpm values. When the stroke is larger than the bore, the engine is undersquared,
with most of its power dependent upon torque.
Which stroke of the four-stroke cycle is shown in the above figure?
a.) Intake
b.) Exhaust
c.) Compression
d.) Power - ANSExhaust - Stage 1: During the intake stage, air that has been mixed with fuel is drawn
into the cylinder.
Stage 2: During the compression stage, the piston rises and compresses the air-and-fuel mixture that's
trapped in the combustion chamber.
Stage 3: During the power stage, the air-and-fuel mixture is ignited by a spark, and the contained
explosion of the fuel presses the piston back down in the cylinder. The downward motion of the piston
is transferred to the rod and crankshaft.
Stage 4: During the exhaust stage, the burned exhaust gases are released from the cylinder. During the
exhaust stroke, the piston rises and the exhaust valve opens. The rising piston pushes the remaining
burned gases in the cylinder out through the open exhaust valve.
Technician A says that horsepower is defined as work per unit of time or the rate of doing work.
Technician B says that one horsepower equals 550 foot-pounds per seconds. Who is right?
a.) B only
, b.) Both A and B
c.) Neither A nor B
d.) A only - ANSBoth A and B - Horsepower is defined as work per unit of time. It's the rate of doing work
or torque and is the unit of measurement that expresses the power output of an internal combustion
engine.
1 horsepower = 550 foot-pounds per second
1 horsepower = 33,000 foot-pounds per minute
During which stage of engine operation does the burning mixture of air and fuel force the piston
downward?
a.) Intake
b.) Power
c.) Compression
d.) Exhaust - ANSPower - During the power stroke, when the piston reaches top dead center, the spark
plug fires and ignites the air-and-fuel mixture. The force created by the exploding fuel gases pushes the
piston down in the cylinder.
The small space above the piston in which fuel is burned is called the _____.
a.) top dead center.
b.) crankshaft.
c.) combustion chamber.
d.) cylinder head. - ANScombustion chamber - When the piston is positioned at the very top of the
cylinder, a small amount of open space is still left between the top of the piston and the cylinder head.
This small, open space above the piston is called the combustion chamber. In the combustion chamber,
a mixture of air and gasoline is burned to produce power.
Technician A says that a ratio is a comparison between to values. Technician B says that in a
compression ratio, the main values are the cylinder volumes at the two different piston positions, BDC
and TDC. Who is right?
a.) Both A and B
b.) A only
