Engine and Emission Control Training (Level 1)
ENGINE AND EMISSION CONTROL TRAINING –
LEVEL 1 EXAM QUESTIONS AND CORRECT
ANSWERS | 2026/2027
ENGINE AND EMISSION CONTROL TRAINING
LEVEL 1
1. In a four-stroke spark-ignition engine, which stroke immediately follows
the compression stroke?
A. Power stroke
B. Overlap stroke
C. Exhaust stroke
D. Intake stroke
A. Power stroke
After the mixture is compressed and ignited, expanding gases force the piston
down on the power stroke.
2. How many crankshaft revolutions are needed to complete one full four-
stroke cycle?
A. Three revolutions (1080 degrees)
B. Four revolutions (1440 degrees)
C. Two revolutions (720 degrees)
D. One revolution (360 degrees)
C. Two revolutions (720 degrees)
Each stroke takes 180 degrees of crank rotation, so four strokes require 720
degrees, or two full turns.
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, Engine and Emission Control Training (Level 1)
3. During valve overlap, which valves are open?
A. Only the exhaust valve
B. Both the intake and exhaust valves at the same time
C. Only the intake valve
D. Neither valve
B. Both the intake and exhaust valves at the same time
Overlap occurs near TDC between the exhaust and intake strokes, when the
exhaust is closing and the intake is opening.
4. Compression ratio is best defined as the ratio of:
A. Cylinder bore to piston stroke
B. Total cylinder volume at BDC to combustion chamber volume at TDC
C. Intake manifold pressure to exhaust pressure
D. Engine displacement to the number of cylinders
B. Total cylinder volume at BDC to combustion chamber volume at TDC
Compression ratio compares the volume above the piston at BDC with the
volume remaining at TDC.
5. Engine displacement is calculated using which values?
A. Compression ratio and engine speed
B. Valve lift and cam duration
C. Torque and horsepower
D. Bore, stroke, and number of cylinders
D. Bore, stroke, and number of cylinders
Displacement equals the swept volume of one cylinder (from bore and stroke)
multiplied by the number of cylinders.
6. In a four-stroke engine, the camshaft turns at what speed relative to the
crankshaft?
A. One-quarter crankshaft speed
B. The same speed as the crankshaft
C. One-half crankshaft speed
D. Twice crankshaft speed
C. One-half crankshaft speed
Each valve opens once every two crank revolutions, so the camshaft is geared
to turn at half crank speed.
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, Engine and Emission Control Training (Level 1)
7. Which component converts the reciprocating motion of the pistons into
rotary motion?
A. Timing chain
B. Camshaft
C. Rocker arm
D. Crankshaft
D. Crankshaft
Connecting rods push on offset crank throws, turning straight-line piston
movement into rotation.
8. Which is NOT a function of the piston rings?
A. Transferring heat from the piston to the cylinder wall
B. Connecting the piston to the connecting rod
C. Controlling oil on the cylinder wall
D. Sealing combustion pressure
B. Connecting the piston to the connecting rod
The piston pin (wrist pin) connects the piston to the rod; rings seal, scrape oil,
and transfer heat.
9. An engine whose bore is larger than its stroke is described as:
A. Long-stroke
B. Oversquare
C. Square
D. Undersquare
B. Oversquare
When bore exceeds stroke the design is oversquare, which favors higher engine
speeds.
10. Detonation is best described as:
A. Spontaneous combustion of the remaining end gas after the spark has fired,
causing a knock
B. Failure of the air-fuel mixture to ignite
C. A smooth, controlled flame front moving across the chamber
D. Ignition of the mixture by a hot spot before the spark occurs
A. Spontaneous combustion of the remaining end gas after the spark has
fired, causing a knock
Detonation happens after normal ignition when unburned end gas explodes;
ignition before the spark is preignition.
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, Engine and Emission Control Training (Level 1)
11. Raising an engine's compression ratio generally requires fuel with:
A. A lower ethanol content
B. A lower octane rating
C. A higher octane rating
D. A higher sulfur content
C. A higher octane rating
Higher compression raises cylinder temperature and pressure, so fuel with
greater knock resistance is needed.
12. Volumetric efficiency compares:
A. Brake power with indicated power
B. Heat converted to work with total heat supplied
C. The actual air drawn into a cylinder with the cylinder's theoretical maximum
D. Fuel burned with fuel delivered
C. The actual air drawn into a cylinder with the cylinder's theoretical
maximum
Volumetric efficiency expresses how well the cylinder fills compared with its
full swept volume.
13. Engine torque is defined as:
A. The heat released per cylinder
B. The rate at which work is done
C. Crankshaft revolutions per minute
D. A twisting force, measured in lb-ft or Nm
D. A twisting force, measured in lb-ft or Nm
Torque is rotational force; horsepower is the rate at which that force does work.
14. At what engine speed are torque (lb-ft) and horsepower values
numerically equal?
A. 3,000 rpm
B. 5,252 rpm
C. 7,500 rpm
D. 6,000 rpm
B. 5,252 rpm
Since horsepower equals torque times rpm divided by 5,252, the two numbers
match at 5,252 rpm.
Page 4 of 49
ENGINE AND EMISSION CONTROL TRAINING –
LEVEL 1 EXAM QUESTIONS AND CORRECT
ANSWERS | 2026/2027
ENGINE AND EMISSION CONTROL TRAINING
LEVEL 1
1. In a four-stroke spark-ignition engine, which stroke immediately follows
the compression stroke?
A. Power stroke
B. Overlap stroke
C. Exhaust stroke
D. Intake stroke
A. Power stroke
After the mixture is compressed and ignited, expanding gases force the piston
down on the power stroke.
2. How many crankshaft revolutions are needed to complete one full four-
stroke cycle?
A. Three revolutions (1080 degrees)
B. Four revolutions (1440 degrees)
C. Two revolutions (720 degrees)
D. One revolution (360 degrees)
C. Two revolutions (720 degrees)
Each stroke takes 180 degrees of crank rotation, so four strokes require 720
degrees, or two full turns.
Page 1 of 49
, Engine and Emission Control Training (Level 1)
3. During valve overlap, which valves are open?
A. Only the exhaust valve
B. Both the intake and exhaust valves at the same time
C. Only the intake valve
D. Neither valve
B. Both the intake and exhaust valves at the same time
Overlap occurs near TDC between the exhaust and intake strokes, when the
exhaust is closing and the intake is opening.
4. Compression ratio is best defined as the ratio of:
A. Cylinder bore to piston stroke
B. Total cylinder volume at BDC to combustion chamber volume at TDC
C. Intake manifold pressure to exhaust pressure
D. Engine displacement to the number of cylinders
B. Total cylinder volume at BDC to combustion chamber volume at TDC
Compression ratio compares the volume above the piston at BDC with the
volume remaining at TDC.
5. Engine displacement is calculated using which values?
A. Compression ratio and engine speed
B. Valve lift and cam duration
C. Torque and horsepower
D. Bore, stroke, and number of cylinders
D. Bore, stroke, and number of cylinders
Displacement equals the swept volume of one cylinder (from bore and stroke)
multiplied by the number of cylinders.
6. In a four-stroke engine, the camshaft turns at what speed relative to the
crankshaft?
A. One-quarter crankshaft speed
B. The same speed as the crankshaft
C. One-half crankshaft speed
D. Twice crankshaft speed
C. One-half crankshaft speed
Each valve opens once every two crank revolutions, so the camshaft is geared
to turn at half crank speed.
Page 2 of 49
, Engine and Emission Control Training (Level 1)
7. Which component converts the reciprocating motion of the pistons into
rotary motion?
A. Timing chain
B. Camshaft
C. Rocker arm
D. Crankshaft
D. Crankshaft
Connecting rods push on offset crank throws, turning straight-line piston
movement into rotation.
8. Which is NOT a function of the piston rings?
A. Transferring heat from the piston to the cylinder wall
B. Connecting the piston to the connecting rod
C. Controlling oil on the cylinder wall
D. Sealing combustion pressure
B. Connecting the piston to the connecting rod
The piston pin (wrist pin) connects the piston to the rod; rings seal, scrape oil,
and transfer heat.
9. An engine whose bore is larger than its stroke is described as:
A. Long-stroke
B. Oversquare
C. Square
D. Undersquare
B. Oversquare
When bore exceeds stroke the design is oversquare, which favors higher engine
speeds.
10. Detonation is best described as:
A. Spontaneous combustion of the remaining end gas after the spark has fired,
causing a knock
B. Failure of the air-fuel mixture to ignite
C. A smooth, controlled flame front moving across the chamber
D. Ignition of the mixture by a hot spot before the spark occurs
A. Spontaneous combustion of the remaining end gas after the spark has
fired, causing a knock
Detonation happens after normal ignition when unburned end gas explodes;
ignition before the spark is preignition.
Page 3 of 49
, Engine and Emission Control Training (Level 1)
11. Raising an engine's compression ratio generally requires fuel with:
A. A lower ethanol content
B. A lower octane rating
C. A higher octane rating
D. A higher sulfur content
C. A higher octane rating
Higher compression raises cylinder temperature and pressure, so fuel with
greater knock resistance is needed.
12. Volumetric efficiency compares:
A. Brake power with indicated power
B. Heat converted to work with total heat supplied
C. The actual air drawn into a cylinder with the cylinder's theoretical maximum
D. Fuel burned with fuel delivered
C. The actual air drawn into a cylinder with the cylinder's theoretical
maximum
Volumetric efficiency expresses how well the cylinder fills compared with its
full swept volume.
13. Engine torque is defined as:
A. The heat released per cylinder
B. The rate at which work is done
C. Crankshaft revolutions per minute
D. A twisting force, measured in lb-ft or Nm
D. A twisting force, measured in lb-ft or Nm
Torque is rotational force; horsepower is the rate at which that force does work.
14. At what engine speed are torque (lb-ft) and horsepower values
numerically equal?
A. 3,000 rpm
B. 5,252 rpm
C. 7,500 rpm
D. 6,000 rpm
B. 5,252 rpm
Since horsepower equals torque times rpm divided by 5,252, the two numbers
match at 5,252 rpm.
Page 4 of 49
