Internal Combustion Engines Flashcards
When working on large engines it may be required to crawl into the engine or turn it over while performing checks. What extra precautions are take when performing these tasks?
Make sure to disable all starting motors, lock out tag out. Starting mechanisms may be pressurized gas on air injection or electric start motors.
What do you need to do when climbing into a crank case?
- inform workers you are entering
- pin, lock, and tag flywheel before entering
If flywheel has been removed or that have no provisions for locking what should you do?
Block engine under the throws of the crank shaft
Parts of an old engine image
Large stationary engines have one head per cylinder. Smaller engines may have?
One common cylinder head to cover all the cylinders
The block is?
Main structure of the engine that supports all working parts to keep them in alignment
Piston rings help seal the in the burning gases to harness as much energy as possible. But they also:
- Control oil consumption
- transfer heat from the piston to the engine block
Connecting Rod is between the piston pin(wrist pin) and?
Crankshaft
Crankshaft changes the linear motion of the piston to?
Continuous usable rotary motion
Camshafts (cams) do what?
Opens and closes the intake and exhaust valves.
Can have extra lobes on it to operate gas valves, air valves, or fuel injectors
Lobes of the of the cam push on _______, which push on the push rods and rocker arms.
Lifters
What is the purpose of the rocker arm?
Change the direction of motion and open valves
What is the purpose of a balancer?
Also known as harmonic balancer, vibration dampener, or torsional vibration dampener.
To reduce crankshaft torsional vibration
What is the purpose of timing gears?
Link the crankshaft, camshaft, balance shafts, ignition systems and other accessories so that all the events in the engine occurs at the correct time
Smaller engines use timing gears while larger engines use?
Chain or belt drives
The engine is a mechanical device that converts ___________ energy stored in a fuel to heat and then to mechanical energy.
Chemical
Engines can be external combustion such as a ________ or internal combustion such as_________.
Steam engine
Gas and diesel engines
What is a motor ?
A mechanical device that converts fluid or electrical energy into mechanical.
A over square engine has a?
(Many high speed engines in cars and small engines are over square)
Larger bore diameter than stroke length
Square engines have?
Same dimensions for bore diameter and stroke length.
Most diesel engines have a under square engine. What does this mean?
Has a longer stroke length than a bore diameter.
Piston displacement of an engine cylinder is the volume swept by the piston when making one complete stroke. What is the formula?
Piston displacement = area of bore x length of a stroke
What is the difference between piston displacement and engine displacement?
Engine displacement is the volume swept by all the pistons in the engine. This is how engines are measure.
Cubic inches, cubic centimetres or litres.
What is clearance volume?
Volume remaining above the piston at TDC.
Compression ratio CR is
Total volume of the cylinder (displacement) and combustion chamber (clearance volume) when the piston is at bottom dead centre to the clearance volume when the piston is at TDC.
Thermal efficiency shows how well the engine converts the energy in the fuel into mechanical energy. Most engines are % efficiency
25 to 35 percent efficiency
Worn rings or cylinders create excessive ?
Blowby this contaminates the oil
Four stroke cycle
- intake
- compression
- power
- exhaust
The four stroke cycle take two revolutions to complete. How many degrees does the crankshaft rotate?
720 degrees
Camshafts, which operate the intake and exhaust valves, turns at _______ the crankshaft speed?
Half
Two stroke engines had how many cycles?
2
How can you determine crankshaft rotation?
By viewing engine from the main power take off or flywheel end. If the engine rotates to the right it is considered a clockwise (CW) if the engine rotates to the left it is counter clockwise (ccw)
SAE stands for
Society of automotive engineers
Why do you need to know cylinder numbering and firing order?
Set engine valves correctly.
What does running mates refer to?
Only on four stroke engines and refer to the cylinders that have pistons reaching TDC at the same time. They are in the same position as each other but not the same stroke.
What does running mates refer to?
Only on four stroke engines and refer to the cylinders that have pistons reaching TDC at the same time. They are in the same position as each other but not the same stroke.
Six common style of cylinder and crankshaft arrangements are:
In line
- v type
- integral
- opposed piston
- horizontally opposed
- radial
What cylinder and crankshaft arrangement is this?
Integral
Which cylinder/crankshaft arrangement is this?
In line
Most common, strong, reliable and easy to produce and work on.
Which is this cylinder/crankshaft configuration is this?
V-type
More compact unit for the power delivered
Common angles are 90 and 60 degree
More torsional vibration making more prone to fatigue problems
Cylinder crankshaft configuration?
Opposed piston
Not common
Horizontally opposed
Used in automotive (volkswagon, Subaru, Porsche) and aircraft applications
High power-weight ratio
Radial
Used in aircraft to save space and weight
Three types of valve arrangements on internal combustion engines?
- over head: most efficient
- multi valve: more efficient but higher cost
- flat head: not used in modern cars may still be used in small 1 or 2 cylinder engines
Over head cams are used in which engines?
Small and intermediate-size engines with one head
Dual over head cam has all the functions of a single overhead came plus?
Allows valves to be arranged in more strategic positions for better efficiency
Most common engine design (cam position)?
Cam in the block (push rod engine)
Two types of cooling methods?
Air - usually small engines less than 200 HP
Liquid - more efficient at regulating engine temperature.
Induction refers to?
How the air enters the engine can either be :
Naturally aspirated
Or artificially aspirated: scavaging pistons, blowers, turbo chargers
Two types of ignition methods?
Compression ignition(CI): diesel
Spark ignition (SI)
Difference between integral engines and engines with a independent load?
Integral type engines built with the load is part of the engine. Example compressor and engine use the same crank shaft and engine block
Independent load engine with an independent load. Very large
Most common type of block?
One piece
Provide more rigidity then multi piece configurations
-
What does underslung crankshaft refer to?
Main bearing caps are under the crankshaft
Multi piece blocks are found in?
Larger-low and medium-speed engines.
Bores can be 10 “ or larger and engine casting become unmanageable.
What is overslung crank shafts?
Main bearing caps are on top of the crank shaft
Why is it important not to use caustic for cleaning aluminum engine components?
Caustic solutions attack and erode aluminum.
When checking a block for coolant leaks you can fit the block with sealing plates and fill with water and pressure test but make sure to not exceed what psi?
45
What do you use to check the cylinder block deck for flatness?
Straight edge and feeler gauges
Check many different spots
If wear or cavities pits cannot be repaired with epoxy what must be done to the counterbore?
Machine and re-sleeve
If the block head is resurfaced what will also have to change?
Piston to head clearance and the block deck height.
Checking main bearing bore alignment on high speed engines is done with what tools?
Straight edge and feeler gauges
Maximum deviation of the main bearing bore should be no more than ________ the maximum allowable main bearing clearance.
Half
How can main bearing misalignment be corrected on high speed one-piece block engines?
Line boring
Checking main bearing bore alignment on larger engines can be done 2 ways:
- if the crankshaft is removed can check with piano wire, laser or optical methods
- if the crankshaft is in place, the alignment of the main bearing bore is checked using a deflection gauge placed between the webs
What tool is used to check bearing bores for size and concentricity?
Inside micrometer or dial bar gauge
When inspecting cylinder liners why is it important to measure bores while they are still in the block?
Some liners are easily distorted so if you measure them outside of the block it might not be accurate
Where is wear on the cylinder bore or liner most Likely to be?
Towards the top of the liner near the upper limit of ring travel and on the major thrust side when cylinder pressure and temperature are at a maximum.
For liners to function properly they must be:
Straight, round and within proper dimensions
What tools are used to check cylinder bores?
Inside micrometer or dial bore gauge
After liners have been removed and are to be reused how must they be stored?
Vertically.
If placed on side they will become distorted and not able to be used
Scoring is
Severe scratches and abrasions along cylinder walls
What is the purpose of the flywheel?
Stabilize speed fluctuations and store energy during power pulses to carry the engine to the next stroke
Where is the vibration dampener (harmonic balancer located and what is its job?
On the opposite end as the flywheel
To cancel out the torsional vibration of in the crankshaft
Vibration dampeners (harmonic balancers) are made with a inertia ring mounted to the hub through a flexible or viscous attachment. These are viscous fluid, rubber or _______?
Springs
Rubber dampeners are often found in which applications?
High speed and automotive applications
Viscous type balancers are used in which application?
Medium and high speed engines
Spring type dampeners are found in which applications?
Low speed and some medium speed applications
Are vibration dampeners repairable? And how are they removed?
No most vibration dampeners are not repairable. With the exception of the spring type.
Use a gear puller to remove
Bias cut connecting rods are used primarily used in _____ engines so it can be removed through the bore.
In line
What is the most accurate of torquing rod bolts?
Bolt stretch(elongation) method
What are the three different rod bolt torquing methods?
Torque wrench - tighten bolts to specified torque
Torque turn method - bolt is torqued to a small prescribed amount to seat the bearing cap. The bolt is then turned an additional number of degrees (manufacturer specifies torque and turn values)
Bolt stretch (elongation method) - bolt length measured before installation, bolt is tightened and then remeasured until the correct amount of stretch is achieved .
What is the purpose of the camshaft?
A loves shaft that changes rotary motion into reciprocating motion.
In a four stroke engine the camshaft is 1/2 the crankshaft speed. How is this achieved?
Camshaft gear is made with Twice as many teeth as the crankshaft gear
Two stroke engines rarely have a camshaft
Camshafts can either be mounted in the block, single over head or _______?
Dual overhead cam
4 stroke timing diagram
What is the purpose of a camshaft lifter(valve lifter)?
Transfer motion to the push rod. Which will move the valves up open and closed.
Three types are hinged roller, roller, mushroom
What are the 5 steps to inspecting camshafts and lifters:
1- visually inspect and measure camshaft journals. Measure and inspect bearings. Measure lobe from base circle to the nose then measure the base circle.
2- check and measure camshaft for straightness (runout)
3- check the camshaft end play after installation and adjust to specs
4 - check cam followers (lifters) for putting and wear. Do not reuse if any pitting or wear.
5 - check cam drive chain for wear. Check gears for wear and backlash
Timing of camshaft is one of the most critical steps in reassembling an engine. The relationship between crankshaft and camshaft is critical. Incorrect timing results in:
- altered valve opening and closing points
- poor engine performance
- damage to engine components
- altered fuel injection timing on engines with camshaft actuated injectors
What is the pushrod?
The link between the lifter and the rocker in a cam-in-block engine.
What are some functions the cylinder head does?
- forms and seals the top of the cylinder that includes a combustion chamber where the compressed air/fuel mixture is burned
- contains the valves and ports which route the flow of the inlet air/fuel mixture and exhaust gases to and from the cylinder
- incorporates passages for the flow of coolant and lubricating oil.
- houses and connects the intake and exhaust manifold and if used, the fuel injectors, air start and gas admissions valves
Valve function ?
Provides means of sealing the cylinder during compression and power events. Also admit the intake charge and expel combustion exhaust gas
What is the purpose of valve springs?
Closing the valves and keeping them firmly against the valve seat.
Worn valve seals cause what?
Oil migrates between valve stem and guide into the combustion chamber. Symptoms are:
Increased oil consumption
Blue exhaust smoke
What do you used to check valve seal for leaking?
Vacuum or solvent test
Most common parts of the cylinder head that require frequent repair or replacement?
Valve guides
Valve
Valve seat
What are different methods for removing valve seats?
- use specific insert puller with and expandable collet
- use a special heeled chisel
- weld a bead on the inside diameter to shrink it
Check valve seat contact by?
- spread thin layer of Prussian blue on the valve face
- insert the valve into the guide and seat it firmly by hand. Do not rotate the valve or you will get false reading
- remove the valve carefully and check the seating. Should show complete contact around the circumference
To wide of a seat there is more area for carbon build and potential leakage. To norrow of a seat causes?
Less contact area which causes poor cooling and accelerated wear.
Whenever the valve operating mechanism has been disturbed to perform cylinder head service, the valve __________ must be adjusted.
Clearance
Exhaust valve clearance is normally ________ than intake valve clearance?
Greater
To allow for greater expansion on the components during engine operation.
Exhaust systems must?
Remove exhaust with minimum restriction and adequate silencing.
Engine exhaust system components are?
Manifold
Piping
Silencer
What does back pressure reduce?
An engines ability to breathe, resulting in loss of power or engine stalling if the back pressure is high enough
Engine overheating causes engine parts to fail, engine over cooling causes the engine to?
Wear and operate inefficiently
The cooling system uses three methods to reject heat:
- conduction
- convection
- radiation
Most engines should run at a temperature range of 82 degrees C to ?
95 degrees C
180 to 200 F
Three types of coolant methods:
Air cooled - have fins on cylinders and heads to circulate air
Liquid cool open system - similar to closed system but coolant is not recirculated. Taken from a water supply and returned to the water supply (lake, pound)
Liquid cooled closed system - coolant is recirculated or reused by sending coolant to a heat exchanger (radiator) to reject the heat.
Parts of a cooling system:
- Water pump and drive
- water jackets
- thermostat
- radiator or heat exchanger
- radiator cap
- expansion or surge tank
- fans and fan drives
- coolant filters
- water manifolds hoses lines
- coolant
If glycol is introduced into the lubrication system what happens?
Oil/glycol Mixture becomes acidic, which damages engine bearings, increases oil viscosity and corrodes engine component surfaces
Three lubricating systems used in modern internal combustion engines?
Splash
Splash/pressure
Full pressure
Lubrication system components:
Oil sump or oil pan
Pickup screen
Oil pump
Filtering system
Oil cooler
Pressure relief valve
What type of positive displacement pumps are commonly found in lubrication system?
External gear pump, but vane, internal gear pump and gerotor pumps are also used.
Maximum system pressure for lubrication system on industrial engines is______ psi?
30 - 60 psi
Modern engines use a full flow oil filtration system and old engines use the ___________ filtration system?
Bypass
Only 5 to 15 % of the oil is passed through the filter before returning to the sump
What are some causes of low oil pressure?
- not enough oil in the crankcase
- higher than normal bearing clearances
- oil viscosity that is to low due to high temperature operation
- worn pump
- plugged pump strainer
-relief valve stuck open or having a broken spring
All industrial engine fuel systems must do the same things regardless of the fuel type. What are they?
Must be able to meter and deliver the fuel into the combustion chamber so that it ca. mix with the compressed air and ignite
Which fuel of gasoline, natural gas, propane or diesel have the highest heat value?
Diesel
What does octane rating mean?
The ability of the fuel to resist ignition due to compression
Higher the octane the more fuel can resist______?
Self ignition
Higher octane numbers burn slower making them easier on engines because they deliver a nice constant combustion versus a quick power blast.
What is cetane rating?
Ability of a fuel to ignite easily under compression
This is advantageous for a diesel engine because there is only air in the cylinder until fuel injection takes place.
High cetane numbers mean fuel is easy to ignite
