Updated 26 May 2025
SGE chapter 3 Questions with Detailed
Verified Answers
Fuel is drawn into the cylinder during the ___ stroke by
the partial ____ created by the ___ movement of the
piston
✓✓ intake, vacuum, downward
In which two strokes are both valves closed
✓✓ Compression and Power strokes
Three key functions performed by the intake valve
✓✓ 1. Open at the correct instant to permit intake of air-fuel mixture
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
✓✓ 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
, Updated 26 May 2025
✓✓ 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"
At what point in the power stroke do most engines
ignite the air-fuel mixture
✓✓ 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
✓✓ ignite
process of exhausting the burned gases from the
cylinder is called
✓✓ scavenging
Exhaust valve may be exposed to pressure as high as
____ pounds per square inch
✓✓ 500
Explain valve overlap and its purpose
SGE chapter 3 Questions with Detailed
Verified Answers
Fuel is drawn into the cylinder during the ___ stroke by
the partial ____ created by the ___ movement of the
piston
✓✓ intake, vacuum, downward
In which two strokes are both valves closed
✓✓ Compression and Power strokes
Three key functions performed by the intake valve
✓✓ 1. Open at the correct instant to permit intake of air-fuel mixture
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
✓✓ 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
, Updated 26 May 2025
✓✓ 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"
At what point in the power stroke do most engines
ignite the air-fuel mixture
✓✓ 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
✓✓ ignite
process of exhausting the burned gases from the
cylinder is called
✓✓ scavenging
Exhaust valve may be exposed to pressure as high as
____ pounds per square inch
✓✓ 500
Explain valve overlap and its purpose
