Engines - 4-Stroke, 2-Stroke, Camshaft, Cylinder Head, Mechanical Components, Compression Ratio, Engine Block Flashcards
List 6 components of a cylinder
Inlet valve
Exhaust valve
Combustion chamber
Piston
Connecting rod
Crankshaft
How many revolutions of the crankshaft is a stroke in a 4-stroke engine?
Half a revolution
What are the 4 strokes of a 4-stroke process? (simple and fancy ways)
Suck
Squeeze
Bang
Blow
Intake
Compression
Power
Exhaust
How many power strokes does a 4-stroke engine cylinder have per crankshaft revolution?
1 per 2 crankshaft revolutions
What do 2-Stroke engines have instead of intake and exhaust valves?
Intake, exhaust and transfer ports
How are the moving parts of a 2 stroke engine lubricated? Why?
By the fuel
Because the crankcase is used in the 2-stroke process
In 2 strokes of a 2-stroke engine, how many times does the piston move up and down each cycle?
Up once, down once
List 3 things that occur in a 2-stroke engine during the first stroke
The exhaust gases flow out of the cylinder
The fuel/air mixture is ignited
The transfer port takes the fuel/air mixture from the crankcase to the combustion chamber
List 4 things that occur in a 2-stroke engine during the second stroke
The reed valve opens and fuel/air goes into the crankcase
The fuel/air in the combustion chamber is compressed
The last residue of exhaust gas flows out of the combustion chamber
In the first stroke of a 2-stroke engine, why does the fuel/air mixture go from the crankcase to the combustion chamber?
The piston moves down, creating pressure in the crankcase as the exhaust fumes exit the combustion chamber
What is the function of a reed valve in a 2-stroke engine?
Ensure that that fuel/air mixture doesn’t flow back into the inlet port
What is another term, sometimes used for the combustion chamber?
The cylinder
In the second stroke of a 2-stroke process, how is a partial vacuum created in the crankcase? (which sucks fuel/air in)
The underside of the piston opens the crankcase up as it closes the combustion chamber, unlike in a 4-stroke engine
How often is the fuel/air mixture ignited in a 2-stroke engine?
Once per revolution (every time the piston is at top dead centre (TDC)
What is the function of the camshaft?
The operation of the valves
What could you compare the shape of a cam to?
An egg
Name the 2 metals that camshafts can be made of
Forged steel, cast iron
List the 3 types of camshaft
Overhead camshaft
Double overhead camshaft
Camshaft with overhead valves
Out of the 3 types of camshaft, which one uses a different camshaft for each valve? (The other 2 use 1 for both)
Double overhead camshaft
Out of the 3 types of camshaft, which one is placed below the piston, connected by a pushrod to the valves which are above?
Camshaft with overhead valves
Name 5 components of a camshaft with overhead valves, in order from bottom to top
Camshaft
Tappets
Pushrod
Rocker
Valves
The intake cam shape can be changed using the buttons. What 2 things will result from a more acute/sharp intake cam shape?
The inlet valve will open later
The inlet valve will close earlier
The intake cam angle can be changed by rotating it. What will result from rotating it so that the bottom of it is more in line will the valve?
The inlet valve will both open and close earlier
Name the process used to influence valve timing
Camshaft adjustment
What 3 materials can cylinder heads be made of?
Aluminium alloys
Magnesium alloys
Cast iron
What is the function of the camshaft? What does it not do, that many think it does?
Opens the valves
Doesn’t close the valves
Why does oil flow through the cylinder head?
To lubricate the valves
What is the head gasket?
A sealing component between the engine block and cylinder head, to prevent combustion gases, oil and coolant from coming into contact with each other
Name 1 factor that is necessary in order for the head gasket to seal properly
The surface must be perfectly flat
There are 3 layers in the head gasket. What is the core made of and what are the seals on the top and bottom of the core made of?
Metal
Graphite
What is used on a head gasket to indicate its thickness?
The holes punched in the corner
Why are there different head gasket thicknesses used for one type of engine?
When the cylinder head has been skimmed, there must be a thicker head gasket to avoid changing the size of the combustion chamber and affecting the compression ratio
How can the flatness/warpage of he cylinder head be checked?
Using a straight-edge and feeler gauge
What kind of bolts are used in the cylinder head? How are these tightened? (3 points)
‘Torque to yield’ bolts
Tightened to torque first, then turned to the right angle, being the yield point
All 10 bolts tightened in a correct order
What is the function of the engine block?
Houses the pistons, connecting rods and crankshaft
What is the function of the cylinder head? (2 points)
Houses the camshaft and valves
Sealing the combustion chamber
What connects the crankshaft to the pistons?
The connecting rod
List 2 functions of the crankshaft
To transfer the rotational movement to the gearbox and wheels
To drive the camshaft
What component drives the camshaft?
The crankshaft
What’s the function of the flywheel?
To make sure the engine runs smoothly
What’s the function of the oil pump?
To circulate oil from the sump to the engine
What’s the function of the coolant pump?
To circulate coolant through the engine block
What is the compression stroke?
A measure of how strongly the air/fuel mixture is compressed during the compression stroke
What does TDC stand for?
What does BDC stand for?
Top dead centre
Bottom dead centre
What is the distance between the piston at TDC and the piston at BDC referred to as?
What is the space above the piston when it’s at TDC referred to as?
What would the 2 of these added together be?
The stroke volume
The combustion chamber volume
Stroke volume + combustion chamber volume = volume of space above the piston when it’s at BDC
Where are core plugs found? What do they do (2 points)?
In the engine block
Stop the engine block from cracking when the coolant freezes and expands
Seal the holes used to cast the block
How do core plugs stop the engine block from being cracked when coolant freezes?
They fill up space, but then get pushed out by the ice, leaving extra space in the engine block
How are cylinders different when the engine block is made of cast iron?
They are bored into the block itself
What in a cast-iron cylinder block provides a low friction coefficient between the cylinder wall and piston?
Cast iron has oil-retaining properties
Give another name for cylinder liner
Dry cylinder liner
Why are wet cylinder liner’s called that?
The liner comes into direct contact with the coolant
List 2 advantages of a wet cylinder liner
Easy to replace
Better heat dissipation
List 4 types of engine block shape
In-line engine
V-engine
Flat 4 engine
Radial engine
What can cause coolant to leak into the oil sump?
A wet cylinder liner not being sealed properly
List 3 factors that the type of engine block used depends on
The drive
The number of cylinders
The installation space
Name the 2 variants of the V engine
W engine
VR engine
Is the in-line or the VR engine longer, if they have the same number of cylinders?
The in-line
