AUTOMOTIVE ENGINES
DIAGNOSIS & REPAIR QUESTIONS
AND THEIR 100% CORRECT ANSWERS
What are the events that take place in an engine?
intake, compression, power, and exhaust
the completion of events constitutes a what?
cycle
In what must the events occur?
proper sequence
What is the definition of a stroke?
the movement of the piston from TDC to BDC
How many degrees of crankshaft rotation in one
stroke?
720 degrees (two turns)
How many revolutions must the crankshaft make to
complete the 4-stroke cycle?
2 revolutions
Do all engines have companion cylinders?
No
During which stroke is the intake and exhaust valves
open in a 4-stroke engine?
They overlap at the end of the exhaust and start of the
intake
In which strokes are the valves closed and why?
Compression: there can't be compression in the cylinder if
the valve is open
,Power: the combustion wouldn't take place if the valves
are open because there is no compression and the gas
would go up and out of the valves
How fast does the camshaft turn in relation to the
crankshaft?
half as fast
What is the compression ratio?
the volume of the cylinder with the piston at BDC
compared to volume at TDC
What factors affect compression ratio?
piston dome size, combustion, volume, head gasket
thickness, deck clearance
What is brake horsepower?
the horsepower at the tires
What is the approximate mechanical efficiency?
90 degrees
What is the approximate thermal efficiency of an
engine?
33 degrees
What is an engine's ability to breathe and what factors
can affect it?
volumetric efficiency; intake and exhaust systems control
VE
What are two different ways to identify an engine?
VIN and casting number
What is the difference between a flat rate manual and
a service manual?
flat rate manual is the time it takes to do the job; service
manual is a device that helps with actually doing the job
What is valve overlap and when does it occur?
, it is when both valves are open at the same time; occurs
at the end of the exhaust and beginning of intake
What determines which of the two possible events
that will occur during a stroke?
cam shaft
What is net horsepower?
horse power of the crankshaft
What are the necessary parts for a combustion
engine?
cylinder, piston, connecting rod, crankshaft, cam shaft and
cam divide, valves and springs, cylinder head, block
What is the definition of torque?
force produced by the crankshaft turning in a circular
motion
What is the procedure for measuring horsepower?
move 550 lbs 1 ft in 1 sec = lbs/ft
What is the definition of a combustion engine?
a heat exchange unit able to produce power from the
expansion of burning gases assembled with parts strong
enough to complete the process. also contains parts to
change from reciprocating (piston) to rotary (crankshaft)
Thermostat
permits rapid warm up; regulates operating temp
Fan assembly
draws air through the radiator; only required at low speed;
belt and electric
Coolant
50/50 mix of coolant and water
Coolant pump
Type of pump used to recirculate a coolant; creates flow
Cooling system
DIAGNOSIS & REPAIR QUESTIONS
AND THEIR 100% CORRECT ANSWERS
What are the events that take place in an engine?
intake, compression, power, and exhaust
the completion of events constitutes a what?
cycle
In what must the events occur?
proper sequence
What is the definition of a stroke?
the movement of the piston from TDC to BDC
How many degrees of crankshaft rotation in one
stroke?
720 degrees (two turns)
How many revolutions must the crankshaft make to
complete the 4-stroke cycle?
2 revolutions
Do all engines have companion cylinders?
No
During which stroke is the intake and exhaust valves
open in a 4-stroke engine?
They overlap at the end of the exhaust and start of the
intake
In which strokes are the valves closed and why?
Compression: there can't be compression in the cylinder if
the valve is open
,Power: the combustion wouldn't take place if the valves
are open because there is no compression and the gas
would go up and out of the valves
How fast does the camshaft turn in relation to the
crankshaft?
half as fast
What is the compression ratio?
the volume of the cylinder with the piston at BDC
compared to volume at TDC
What factors affect compression ratio?
piston dome size, combustion, volume, head gasket
thickness, deck clearance
What is brake horsepower?
the horsepower at the tires
What is the approximate mechanical efficiency?
90 degrees
What is the approximate thermal efficiency of an
engine?
33 degrees
What is an engine's ability to breathe and what factors
can affect it?
volumetric efficiency; intake and exhaust systems control
VE
What are two different ways to identify an engine?
VIN and casting number
What is the difference between a flat rate manual and
a service manual?
flat rate manual is the time it takes to do the job; service
manual is a device that helps with actually doing the job
What is valve overlap and when does it occur?
, it is when both valves are open at the same time; occurs
at the end of the exhaust and beginning of intake
What determines which of the two possible events
that will occur during a stroke?
cam shaft
What is net horsepower?
horse power of the crankshaft
What are the necessary parts for a combustion
engine?
cylinder, piston, connecting rod, crankshaft, cam shaft and
cam divide, valves and springs, cylinder head, block
What is the definition of torque?
force produced by the crankshaft turning in a circular
motion
What is the procedure for measuring horsepower?
move 550 lbs 1 ft in 1 sec = lbs/ft
What is the definition of a combustion engine?
a heat exchange unit able to produce power from the
expansion of burning gases assembled with parts strong
enough to complete the process. also contains parts to
change from reciprocating (piston) to rotary (crankshaft)
Thermostat
permits rapid warm up; regulates operating temp
Fan assembly
draws air through the radiator; only required at low speed;
belt and electric
Coolant
50/50 mix of coolant and water
Coolant pump
Type of pump used to recirculate a coolant; creates flow
Cooling system
