Engine Fundamentals Flashcards
What is compression ratio?
The ratio from BDC to TDC
What is the best way to describe the noise caused by piston slap?
Hollow bell like noise
What engine test can be used to pinpoint the cause of a low cylinder compression test result?
A cylinder leakage test
What could be the cause of indicated by good results from a compression test but poor results from a cylinder power balance test?
A collapsed lifter
What are the best names for the four-strokes?
Intake, Compression, Power, Exhaust
What is piston slap?
Noise made by the piston when it contacts the cylinder wall
During a cylinder leakage test where would you expect to find/ hear the air from if the piston rings were worn?
The oil fill port, dipstick tube
During a cylinder leakage test where would you expect to find/ hear the air from if a leaking intake valve was present
Throttle plate
During a cylinder leakage test where would you expect to find/ hear the air from if a leaking exhaust valve was present
Exhaust pipe
During a cylinder leakage test where would you expect to find/ hear the air from if a head gasket is blown
Radiator
What is the stroke of the piston equal to
Two times the crankshaft throw
What is an expression of how much of the heat formed during the combustion process is available as power from the engine
Thermal efficiency
Which stroke in the four stroke cycle begins as the compressed fuel mixture is ignited in the combustion chamber?
Power Stroke
What would cause a sharp metallic rapping sound that originates in the upper portion of the engine and is mist pronounced during idle?
Worn piston pins
As an engines compression ratio increases, what should happen to the octane rating of the gasoline?
It should increase to avoid detonation
What engine type typically has the highest compression ratio?
Diesel
What would cause a higher than normal oil pressure test reading?
A defective oil pressure regulator valve
What engine component is responsible for opening and closing the intake and exhaust valves?
Camshaft
What test can be performed to check the efficiency of individual cylinders?
Cylinder balance test
Tappet noise is best described as
Noisy Valve train components
RTV is ________
Aerobic
Explain Firing order
The order in which an engines pistons are on their compression stroke and the order in which the spark plugs ignite.
What is the bore of a cylinder
The cylinders diameter measured in mm or in
What is the stoke
The distance the piston travels between TDC and BDC
What does the bore and stroke determine
The displacement of the cylinders
What does a square engine refer to
When the bore and stroke are equal sizes
What is an oversquare engine
Engines that have a larger bore than stroke
What is an undersquare engine
Engines that have a larger stroke than bore
Which kind of engine can be fit with larger valves and shorter connecting rods and are more capable of running at higher speeds?
Oversquare Engines
What engines use longer connecting rods that aid in the production of more power at lower engine speeds?
Undersquare Engines
What is crank throw
The distance from the crankshafts main bearing centerline to the crankshaft connecting rod journal.
What is a cylinders displacement
The swept volume of the cylinder. The volume of the cylinder from BDC to TDC.
An engines displacement is ___________
The sum of the displacements of each of the engines cylinders
The higher the compression ratio ________
The more power an engine can produce
Volumetric Efficiency refers to :
The engines ability to fill its cylinders with the air fuel mix
Thermal Efficiency refers to:
A measure of how much of the heat formed during combustion is available as power from the engine.
What can increase Volumetric Efficiency?
Turbochargers and Superchargers
What is Mechanical Efficiency?
Power available vs. power exherted
Torque is : ________
A twisting or turning force
Horsepower is : ___________
The rate at which the torque is produced
Which four stroke engine holds the intake valve open longer during the compression stroke?
Atkinson Cycle Engine
An Atkinson cycle engine with forced induction (supercharger) is called what?
A Miller Cycle Engine
What happens to engine vacuum as rpms increase if the throttle plates are closed
Vacuum will increase
What happens to engine vacuum when the throttle plates are open
Vacuum will decrease
What is Ring Noise and when can it be heard
Can be heard during acceleration as a high-pitched rattling or clicking in the upper part of the engine.
What can cause Ring Noise
Worn rings or cylinders, broken piston ring lands, insufficient ring tension against the cylinder walls
When is Piston Slap commonly heard?
When the engine is cold and often gets louder with acceleration
What does Piston Pin Knock sound like
A sharp metallic rap that can sound more like a rattle if all the pins are loose
What is Rod Bearing Noise and when is it most commonly heard?
It is the result of worn or loose connecting rod bearings and is most commonly heard at idle or cruising speeds and during deceleration.
What causes Piston Pin Knock
Worn Piston pins, piston pin bushing, lack of lubrication
What is Detonation often caused by?
Advanced ignition timing, substantial carbon build up, Fuel octane that is too low
What does a basic short block consist of?
The block, crankshaft, crankshaft bearings, connecting rods, pistons and rings, and oil gallery and core plugs
Chamfering or counterboring will __________
Eliminate thread pulls and jagged edges
Taper is _____________
The difference in diameter between the bottom of the cylinder bore and the top of the bore. Subtracting the smaller diameter from the bigger one
What causes glaze on cylinder walls?
Combustion heat, engine oil and piston movement
Bearing spread ensures : ______________
Positive positioning against the inside of the bore and helps keep bearings in place during assembly
What are crankshafts generally made of?
Cast iron,cast steel and nodular iron
What is Plastigage and what is it used for
A fine plastic string used to measure the oil clearance between the bearing and the crankshaft
The connecting rod helps: ________
Transmit the pressure applied on the piston to the crankshaft
Maximum valve margin clearance is
1/32 of an inch
What can cause oil to enter the combustion chamber
Worn valve seats and guides, worn piston rings
How do you calculate cylinder displacement?
pie x r2 x stroke
How much pressure does a cylinder head gasket have to hold
1500 psi
Many camshafts use what instead of bearing inserts
Aluminum supports
Max allowable warpage of a V8 cylinder head is?
0.004 in
Max allowable warpage of a V6 cylinder head is?
0.003 in
Max allowable warpage of an inline 6 is?
0.006 in
How do you correct excessive valve stem height?
Grind the material from the valve stem tip
When should a valve be discarded
If it has cracks or it has damaged keeper grooves
What is recommended before removing the valves from a cylinder head?
Measure the valve spring height
How many degrees of crankshaft rotation are required to complete a four stroke cycle in one cylinder?
720
What is the procedure for removing cylinder head bolts?
They are removed in the reverse order of assembly
Low compression in two side by side cylinders is likely what?
A leaking head gasket
Valves being ground with an interference angle is referring to the angles between what components?
Valve face and valve seat
How are integral valve guides reconditioned?
By installing bronze guides and reaming the guide for an oversize valve stem
To narrow and lower a 45 degree valve seat the tech should use a _____________ stone
30 Degrees
To widen a 45 degree valve seat without raising or lowering its position the tech should use a ________ stone
45 degree
What are valve springs checked for?
Tension, free height and squareness
What type of valve spring uses two springs wound in opposite directions?
Dual springs
How is excessive valve stem height usually corrected?
Replacing the valve seat
Valve spring installed height can be adjusted by
Installing valve spring inserts (shims)
Which type of valve seal moves up and down with the valve?
Umbrella seals
What is required of the valve face contact surface to ensure proper seating of the valve
It should be concentric with the guide
Why do multiple valve engines tend to be more efficient than engines with two valves per cyl
They provide less restriction to the airflow
O ring seals are located where on the valve stem
Between the stem and the valve guide
Crankshaft endplay can be checked with
Feeler gauge, Dial indicator
What does bearing crush help
Ensure good contact between the bearing and the housing
The maximum taper and out of roundness of a crankshaft journal is
0.001 in
What are the two basic designs of bearing inserts?
Full round (one piece) , Split (two piece)
3 Types of core plugs
Expansion, Dished and Cup
What material are camshaft bearings made of?
Aluminum or steel with a lining of babbitt
Common compression rings are made of
Cast iron, Cast iron coated with moly, Cast coated with chrome
Most common ways to measure cam lobe wear
Dial indicator and outside micrometer
What are the three names of piston rings on modern day pistons
Top compression, Bottom compression and oil control ring
What is cylinder boring
When surfaces are badly worn or excessively scored or tapered boring is done to cut the cylinders for oversize pistons or sleeves
What is cylinder honing
The use of honing stones to deglaze and replace the crosshatch finish that is necessary
What are most modern day pistons made of?
Aluminum alloyed with, copper, magnesium, nickel and silicon
What are the two types of basic piston skirts?
The slipper and full skirt
What are the three reasons for resurfacing the deck surface of a cylinder head
To make the surface flat
To raise compression ratio
To square the deck to the main bores
In general the maximum deformation of a cylinder head allowed is
0.004 in
Today most valves are made from _______
Special hardened steel, steel alloys, or stainless steel
Out-of-roundness is
measured at the top of
the cylinder just below
the ridge. Typically, the
maximum allowable out-of-
roundness is
0.0015 in
