Engines (All Modules) Flashcards
What is it called when the main bearing caps are under the crank shaft?
An underslung crankshaft
What is it called when the crankshaft is laid on a bed plate and the main bearing caps are on top of the crankshaft?
An overslung crankshaft
What should you not use when cleaning aluminium?
Caustics
Strong corrosive
What measurements change if the block deck is resurfaced?
The piston to head clearance and the block deck height changes
How can you check for crankshaft deflection if the crankshaft is still in the housing?
You can use a deflection gauge placed between the webs and rotate the crank to see if the space between changes.
What is line boring?
A procedure that uses a boring bar to machine the main bearing bores
What are other names for cylinders?
Liners or sleeves
What are the main functions of a cylinder? (Liners, sleeves)
To be able to,
Withstand high heat And high pressures from combustion.
Dissipate heat and keep the coolant out of the crankcase.
Cylinders also have a large affect on sealing the combustion gases.
Where is the highest wear area on a cylinder?
Near the top of the line due to high temperatures, pressures and minimum lubrication
What are some of the methods used to treat the inside of cylinder liners in order to reduce the rate of wear?
Induction hardening
Hard chrome
Nitriding
What are dry liners?
They are sleeves that fit inside the cylinder bore and do not contact the engine coolant
What are wet liners?
Liners that are in contact with the coolant and form part of the water jacket
Why should you measure a liner while it is still in the block before you remove it?
It may warp or expand when removed from the block. So take measurements while it is still in the block to see if it can be reused.
What is the best tool for taking bore measurements?
Dial bore gauge
What is scoring of a cylinder?
Severe scratches and abrasions along the cylinder walls
What usually causes liner cracking?
Over heating, hot spots or piston seizure
What is cavitation of a cylinder liner?
Where small pinholes appear on the coolant side of the liner, if the holes get deep enough, the coolant enters the cylinder and mixes with the lube oil
What is deglazing of a cylinder?
If a cylinder measures within specifications for reuse, deglazing is done with a flexible hone or ball deglazed. This removes polished or glazed surfaces and produces a cross-hatch pattern in the cylinder.
What angles should a cylinder cross hatch patter be?
40° - 60°
What should you use to clean the cylinder after honing or deglazing?
What should you not use?
You should use a bristle brush and hot soapy water
Don’t use a solvent because it does throughly flush the material and abrasives from the microscopic grooves.
What is honing? (Rigid honing)
Rigid honing is done to make the cylinder straight and round
Misaligned main bearing bores could cause what?
Excessive bearing wear or a broken crankshaft
Why do you use alloy cast iron for an engine block material?
The alloy cast iron is very strong
What do leaking o-rings on a wet liner cause?
Coolant to enter the crankcase
What is the purpose of the crankshaft?
To convert downward linear motion of the piston to usable rotary motion
What are the parts of a crankshaft?
Main bearing journals
Connecting rod journals/throws
Webs
Counterweights
What is a flywheel for?
To stabilize speed fluctuations and store energy during power pulses to carry the engine to the next stroke
What are vibration dampeners?
Balancers, harmonic balancers
To reduce crankshaft torsional vibration
What are the 3 different types of vibration dampeners?
Rubber mounted
Viscous-type dampeners
Spring-type
What is fatigue strength of a plain bearing?
The ability of the bearing to withstand shock loads without flaking or cracking prematurely
What is conformability of a plain bearing?
The ability of the bearing to mould itself to the imperfections of the crank journal
What is embeddability of a plain bearing?
The ability of the bearing to absorb small particles of dirt, thereby preventing damage to the shaft
What is bearing spread?
When the bearing half is wider the the bore that is going to be installed. This gives the bearing a tight fit in the bearing cap and housing during installation
What is bearing crush?
When the bearing inserts are machined to protrude out from the bearing cap and housing. This is to achieve a tight fit during installation by forcing the bearings against the bearing cap and housing when it is torqued together
What are 4 ways of measuring bearing clearance?
Measurement of the shaft and the bearings inside diameter
Plastigauge
Lead wire
Bearing lift checks
What are the most common causes of bearing failure?
Lack of lubrication
Contaminated oil
Misalignment
What are connecting rods?
They form the link that transmits the force of combustion in the cylinder from the piston to the crankshaft
What are the 2 types of connecting rods? What is the difference?
Straight cut, has a parting line that is 90° to the rod beam
Bias cut, this is cut at an angle to reduce the with when the 2 parts are separated
If you don’t see match marks when removing rod caps, what should you do?
Match mark them!
What are the various piston rod cap alignment devices?
Rod bolts which have a close fit
Dowels
Tongue and groove
Serrated (saw tooth)
What is the purpose of a piston?
To receive and withstand the high temperature-high pressure force of the expanding gases caused by the combustion
What are the purpose of piston rings?
To make a dynamic seal between the piston and the cylinder walls and to dissipate heat from the piston to the cylinder walls
Why might the top of a piston be irregularly shaped?
To create turbulence within the cylinder to mix the air and fuel
What is a trunk type piston?
A one piece piston that can be forged or cast, it has a longer skirt to provide more support and quieter operation
What is a cross head type piston head?
It’s a 2 piece piston where the top part of the piston with the ring lands is one part and the skirt is the second
What are the various ways for piston cooling and lubrication?
Spray oil from a nozzle that is directed at the underside of the piston
Oil that is pumped through the rod lubrication passage to a compartment in the top of the piston
What are the 3 types of piston pins?
Full floating pins, free in the rod and piston
Locked-to rod pins, that turn in the piston only
Locked-on piston, pins are held in the piston while the rod turns on the pin
What are the 2 types of rings used on a piston?
Compression rings
Oil control rings
How are compression rings activated?
By gas pressure that forces the ring outward and down to seal
What are the common types of ring joints for compression rings?
Angle joint
Step joint
Straight butt joint
How should ring gaps on compression rings be lined up when installed?
They must be staggered to prevent leakage
What is a camshaft and what does it control?
It’s a loved shade that changes rotary motion into reciprocating morning, the camshaft controls the opening and closing of the intake and exhaust valves
How fast does the camshaft on a 4-stroke engine spin compared to the crankshaft?
The speed of the camshaft is 1/2 crankshaft speed on a 4-stroke engine
What are the 3 types of lifters?
Solid
Roller
Hydraulic
What is the purpose of the camshaft lifter?
To transfer motion to the pushrod
What is a pushrods purpose?
It serves as a link between the lifter and the rocker arm in a camshaft-in-block engine.
It may be a solid rod or a hollow tube that carries oil to the rocker arm and pivot
What us a rocker arm and what is it’s purpose?
It’s a mechanical link between the pushrod and the valve, changing the upward motion of the lifter and pushrod into a downward motion of the valve.
What is a valve bridge/cross head?
It is a bridge that spans a pair of intake or exhaust valves and allows one rocker arm to open both valves simultaneously
What is the function of the cylinder head?
It forms and seals the top of the cylinder that includes a combustion chamber where the compressed air/fuel mixture is burned.
It also incorporates passages for the flow of coolant and lubricating oil
How are engine valves primarily cooled?
Through heat stranded to the valve sear and guide
What is a valve rotator and what is it’s purpose?
It cause the valve to rotate slightly every time the valve actuated, it is used to help break carbon deposits on the valve seat and promotes even wear on the valve and seat
What is valve clearance? (Lash)
It is small a gap between the rocker arm and the top of the valve
It is there to provide clearances for component expansion as engine temperatures rise and to compensate for wear in the valve operating system
When you adjust valve clearance what position must the valves be in?
A closed position
When compared to an integral valve seat, valve seat inserts provide a replaceable wear surface with improved ______
Wear characteristics
Why is an exhaust valve usually made of higher quality material then an intake valve?
It operates at a higher temperature and is subject to corrosive gases flowing through
What are the 2 types of cam arrangements?
Can in block arrangement
Overhead cam arrangement
Valve seals control valve guide and stem lubrication to prevent what?
Oil consumption
What is a BTU?
A British Thermal Unit
Amount of head required to head 1 lb of water by 1°F
What is a calorie?
Amount of heat necessary to heat 1g of water by 1°C
What does octane rating refer too?
The ability of the fuel to resist ignition due to compression
What does a higher octane number show?
The more the fuel can resist
self-ignition
What does Cetane refer too?
The ability of a fuel to ignite easily under compression
What is pre-ignition?
This occurs before there is a spark from the ignition system to the spark plug, it is caused by hot spots in the combustion chamber
What is detonation?
Occurs later then pre-ignition in the combustion process, the flame travels from the plug across the combustion chamber, as the fuel is burning the flame causes the fuel mixture on the opposite side of the combustion chamber to be compressed even higher then it is already compressed from compression.
What are the two basic methods of gasoline fuel systems?
Carburetor
Electronic fuel injection
What does a carburetor do?
Atomizes the fuel and mixes it with the air in the proper ratio
What is a Venturi on a carburetor?
A restriction in the air horn that creates a low pressure area in the carburetor.
How does the main discharge tube of a carburetor allow fuel to enter the air horn?
It has atmospheric pressure in the bowl where the fuel is and a low pressure area at the end of the fuel causing the fuel to flow through the tube because of the difference in pressure
What are the 2 basic methods used to meter the fuel in a computer controlled electronic fuel injection system?
Varying the fuel pressure
Opening the injector in pulses
What is a knock sensor?
A sensor that is attached to the block or the head to indicate whether there is pre-ignition or detonation
Where is the fuel injected in a gasoline engine?
The intake manifold or the intake port
What are the 2 basic types of natural gas fuel systems?
Carbureted
Fuel injected
What is needed between the fuel and air inlet pressure at the carburetor?
The gas must always have a higher pressure then the air pressure to ensure there is always gas entering the engine
How is carburetor linkage setup?
It is set up so that a very small movement of the governor does not cause a large initial movement of the throttle in its most sensitive positions
What is the issue with throttle shaft seal leaks?
It allows unfiltered wire into the engine which can cause significant wear
Where is the fuel mixed on a two stroke
Natural gas engine that uses a low pressure fuel injection system?
In the engine cylinder. The air and fuel are not premixed before entering the cylinders
The air enters the cylinder at bdc and the fuel is not injected into the cylinder until the piston moves up and covers the exhaust ports.
What does LPG stand for?
Liquid petroleum gas
Between gasoline, natural gas, propane and diesel. Which of these has the highest heat value?
Diesel has the highest heat value
How much should you a propane tank be filled to and why?
80% because propane expands very rapidly when there is a temperature increase
What are the 2 types of carburetors used when using propane?
Air valve carburetors
Spray bar carburetors
What does the metering valve control and what does the throttle plate control on a spray bar mixer?
The metering plate controls the fuel
The throttle plate controls the air
How does a diesel fuel system ignite the fuel?
Using the heat of compression
What is a necessary thing a diesel fuel injection pump must do?
Inject a high enough pressure to overcome and penetrate the highly compressed air
What are the two basic types of diesel fuel injection systems?
Mechanical injection/mechanical control
Mechanical injection/electronic control
How does a distributor fuel injection system work?
It has one high pressure pumping plunger the distributed and pumps fuel to a distribution head. The distribution head than diverts fuel to each of the injector nozzles
How does an inline fuel injection system work?
It is a self contained unit that has its own cam and plunger for each cylinder
What is the port and helix metering method?
When each plunger pump is feared to a rack that is controlled by the governor. The position of the governor linkage adjusts the rack, which then rotates the plungers in their bore. This changes the position of the plunger helix port for when fuel is delivered to the injector.
How does a unit fuel injection work?
Is has the injector pump and injector mounted in the head of the engine
What are the primary functions of an air induction system?
- To clean the air so that it is free of abrasive particles
- Ensures a sufficient quantity of air is supplied
- Ensures air is at the correct temperature
- Also aids in cooling the valves and other internal parts
What’s the most common way an oil bath air cleaner works?
It directs the air to make a sharp corner, at which point the air encounters the oil, the first particles are then caught in the oil.
What is a u-tube manometer used for?
A primary measuring device the indicates pressures or vacuums by the difference in the height of two columns of fluid.
What are the most common ways of induction?
Natural aspiration
- relies on atmospheric pressure to push air into the cylinders
Artificially aspirated
- uses some mechanic means to push the air into the cylinder
Piston-type scavenging pumps
- uses the underside of the piston and a sealed crankcase to push air into the cylinder
Blowers
- lobed blowers, centrifugal blowers
What is supercharging?
Process of increasing the mass of air in the engine cylinders by raising the air density and pressure in the cylinder to above atmospheric pressure, this allows more fuel to be burned.
What is turbo charging?
Uses the exhaust gases to spin a turbocharger exhaust wheel that is attached to the intake compressor wheel. This causes both wheels to spin at the same high rate of speed.
What is the term used for pressure produced by the turbo charger?
Boost
What is a ignition system distributor?
A device that distributed electrical power to each system in the correct sequence and at evenly spaced intervals
What is a diode?
A solid state decides that allows current to flow in only one direction
What is a zener diode?
A solid state voltage-regulating device that can be specified for a specific voltage or voltage rating
What is a transistor?
An electronic switch that is turned on by a small current to one of its connections.
What is a bridge rectifier?
A solid state device that changes AC current into DC current
What is a magneto ignition system?
An ignition system that produces its own power by using permanent magnets in its own generating system
What is a microprocessor-type ignition system?
An ignition system that has no moving parts and are fully computerized
What are the 2 distinct circuits of all ignition systems?
The low voltage primary circuit
The high voltage secondary circuit
What is an ignition coil?
A step-up transformer that converts low voltage, high current electrical energy into high voltage, low current electrical energy
Which component do you use to control boost on a turbocharger?
The waste gate
How do you determine the heat range of a spark plug?
The heat path is from the tip of the centre electrode, through the ceramic insulator to the steel shell. The shorter the length of this path, the cooler the spark plug operates.
What 2 components do you use in a compression ignition (CI) system for cold starting?
Glow plugs
Intake manifold heaters
What are the 4 methods you can crank an engine over for starting?
Use an electric motor
Air start with an air rotor
Air start with direct air injection
Hydraulic motor
What is the main function of an engine cooling system?
To regulate engine temperature
What are the three methods an engine cooling system uses to reject heat?
Conduction
Convection
Radiation
What are the three types of cooling systems?
Air cooled engines
Liquid cooling open system
(Coolant is not recirculated)
Liquid cooling closes system
(Coolant is recirculated)
What is the function of a thermostat?
To sense engine temperature and maintain operating limits by controlling coolant flow
Where most a cooling system expansion tank be located?
Above the engine
What type of pump is a water pump?
A centrifugal, non-positive, displacement type pump
What are the 2 main types of coolant and which one is safer for the environment?
Ethylene Glycol (High boiling point)
Propylene Glycol
(Safer for the environment)
(Lower boiling point)
What happens if glycol is introduced into the lubrication system?
The oil/glycol mixture becomes acidic and damages engine parts and surfaces
What are 2 tools used to test antifreeze strength?
A hydrometer
A refractometer
What are the 3 types of lubrication methods?
Splash system
Splash/pressure system
Full pressure system
What type of pump is used on an engines main lubrication system?
Positive displacement rotary pump
Ex. External gear type Vane Internal gear Gerotor pumps
What are the 2 types of oil filtration systems?
Full-flow filtration
Bypass filtration system
What are some of the considerations that affect oil and filter changes?
Type of fuel burned and the quality of the fuel
The environmental conditions in which the engine operates
The amount of oil in the sump and the extent of the filtration systems
What is the purpose of a crankcase ventilation system?
To remove combustion gases and water vapours from the crankcase
What is it called when combustion gases escape past the piston rings and enter the crankcase?
Blow-by
What is the purpose of the exhaust manifold?
To collect the exhaust gas
How does a muffler accomplish sound silencing?
By changing the direction of gas flow multiple times
What are the 5 functions of a lubrication system?
To reduce friction To cool To seal To clean To absorb loads
What instrument is commonly used to check the crankcase ventilation system?
Manometer
What should the mass be of a complete engine foundation?
2.5 times the mass of the complete engine
Typically, How thick are the rubber separators places between the building foundation and the engine mounting block?
3/4” thick
What are the 2 basic types of engine mounting?
Skid mount
Block mount
What are sole plates?
The load bearing steel plates grouted into the foundation around the mounting area of the foundation
What are the 2 types of engine control systems?
Electronic
Pneumatic
What are the three types of maintenance programs?
Reactive
Preventative
Predictive
What is the main purpose of an engine control system?
To monitor and control the engine and to shut down an engine in the event of a critical alarm
