1 promax - Stuvia US 2025/2026
SGE chapter 3 Questions with Detailed Verified Answers
(100% Correct Answers) /Already Graded A+
Fuel is drawn into the cylinder during the ___ stroke by the partial ____
created by the ___ movement of the piston
Ans: intake, vacuum, downward
In which two strokes are both valves closed
Ans: Compression and Power strokes
Three key functions performed by the intake valve
Exampromax - Stuvia US
Ans: 1. Open at the correct instant to permit intake of air-fuel mixture
Approved By:
2. Must close at the correct time and seat during compression
3. Shape must be streamlined, so flow of gases into combustion chamber
will not be obstructed
why do intake valves usually last longer than exhaust valves
Ans: Bc there are not subject to as high a temperature as the exhaust valves
do
Two reasons that explain how the compression stroke increases the force
of combustion
Ans: 1. When atoms of air and fuel are squeezed close together, heat
energy is created. Each molecule of food is heated almost to its flash point,
and combustion is almost instant and uses the whole mixture
2. Tightly packed molecules are highly activated and are striving to move a
part - this energy adds a "tremendous force against the piston"
, 2 promax - Stuvia US 2025/2026
At what point in the power stroke do most engines ignite the air-fuel
mixture
Ans: When the pison compresses the charge & reaches the top of the
cylinder, causing an electrical spark to jump the gap ("power stroke")
If the compression ratio is too high the fuel may be heated to its flash point
and _____ too early
Ans: ignite
process of exhausting the burned gases from the cylinder is called
Ans: scavenging
Exampromax - Stuvia US
Exhaust valve may be exposed to pressure as high as ____ pounds per
Approved By:
square inch
Ans: 500
Explain valve overlap and its purpose
Ans: it occurs when both valves are open at the same time and is meant to
create a partial vacuum in the cylinder & help initiate a mixture of fuel int
eh cylinder
Explain why the intake valve does not close until after bottom dead center
Ans: It allows for extra air to come in from the momentum of the mass of
the air moving
how does a mechanic know that the valves are timed properly
Ans: if the timing marks on the crankshaft and camshaft gears are aligned
SGE chapter 3 Questions with Detailed Verified Answers
(100% Correct Answers) /Already Graded A+
Fuel is drawn into the cylinder during the ___ stroke by the partial ____
created by the ___ movement of the piston
Ans: intake, vacuum, downward
In which two strokes are both valves closed
Ans: Compression and Power strokes
Three key functions performed by the intake valve
Exampromax - Stuvia US
Ans: 1. Open at the correct instant to permit intake of air-fuel mixture
Approved By:
2. Must close at the correct time and seat during compression
3. Shape must be streamlined, so flow of gases into combustion chamber
will not be obstructed
why do intake valves usually last longer than exhaust valves
Ans: Bc there are not subject to as high a temperature as the exhaust valves
do
Two reasons that explain how the compression stroke increases the force
of combustion
Ans: 1. When atoms of air and fuel are squeezed close together, heat
energy is created. Each molecule of food is heated almost to its flash point,
and combustion is almost instant and uses the whole mixture
2. Tightly packed molecules are highly activated and are striving to move a
part - this energy adds a "tremendous force against the piston"
, 2 promax - Stuvia US 2025/2026
At what point in the power stroke do most engines ignite the air-fuel
mixture
Ans: When the pison compresses the charge & reaches the top of the
cylinder, causing an electrical spark to jump the gap ("power stroke")
If the compression ratio is too high the fuel may be heated to its flash point
and _____ too early
Ans: ignite
process of exhausting the burned gases from the cylinder is called
Ans: scavenging
Exampromax - Stuvia US
Exhaust valve may be exposed to pressure as high as ____ pounds per
Approved By:
square inch
Ans: 500
Explain valve overlap and its purpose
Ans: it occurs when both valves are open at the same time and is meant to
create a partial vacuum in the cylinder & help initiate a mixture of fuel int
eh cylinder
Explain why the intake valve does not close until after bottom dead center
Ans: It allows for extra air to come in from the momentum of the mass of
the air moving
how does a mechanic know that the valves are timed properly
Ans: if the timing marks on the crankshaft and camshaft gears are aligned
