1. Internal Combustion Engine
Operation
&
Design

2. Learning objectives Internal Combustion Engine Operation
Fuel & The Four Stroke Engine
The Four Stroke Cycle
Engine Components & Sub Assemblies

3. Learning objective
Internal Combustion Engine Operation

4. Internal Combustion Engine Operation
It is important to know and understand that there are several types of internal combustion engines but they all operate on the same basic principle or concept.
Types of Internal Combustion Engines
Two Stroke (Lawn Equipment, R.C. Hobby, Dirt Bikes, and Small Boats)
Four Stroke (Cars, Trucks, SUV, Generators)
Rotary (Wankle Design Mazda RX 8, Helicopters)
Turbine (Jets)
Rockets (Space Flight)

5. Internal Combustion Engine Operation
Two Stroke, Four Stroke, Rotary, Turbine, & Rockets
What do these Internal Combustion Engines Have in Common?
While the overall design of these internal combustion engines is vastly different they all operate or function by converting an fuel/air mixture into heat inside a combustion chamber.
The purpose of the internal combustion engine is to convert stored chemical energy into kinetic energy or the energy of motion.
In this unit we will focus our attention on the four stroke internal combustion engine because most highway automobiles operate on the 4 stroke cycle.

6. Learning objective
Fuel & The four Stroke Engine

7. Fuel & The four stroke engine
There are 3 common fuels used in four stroke engines
Diesel Fuel
Ethanol
Gasoline

8. Fuel & The four stroke engine
Diesel Fuel
Named after Rudolf Diesel the inventor of the four stroke diesel engine in 1894, Diesel fuel is a type oil that has a relatively low flash point of about 205ºF. Diesel oil will ignite within the combustion chamber as a result of the extreme heat generated on the compression stroke of the four stroke cycle. Because of diesel fuels low flash point and the diesel engines high compression ratio diesel engines do not require ignition systems for combustion to take place. Instead they use glow plugs to raise the temperature inside the combustion chamber on the first cycle of the four stroke process. Diesel Fuel is the leading fuel for heavy equipment like trains, heavy trucks, ocean vessels, power generators, and tractors.

9. Fuel & The four stroke engine
Ethanol
Ethanol is another name for denatured alcohol or pure grain alcohol. Ethanol was one of the first alternatives to diesel fuel. One of the earliest mass produced vehicles to operate on Ethanol was Henry Fords Model T. Prohibition in the 1920’s included alcohol produced for fuel so after 7 years of production Henry Ford switched to gasoline to power his engine. After this ethanol was not used as a common fuel until the late 1990’s when it was used as a 10% additive to gasoline
After the turn of the century fuel manufacturers began to market E85 a mixture of 85% ethanol to 15% gasoline.
While ethanol will work in modern gasoline engines it will corrode the fuel delivery components. Ethanol has once again claimed it status as an alternative fuel in passenger vehicles.

10. Fuel & The four stroke engine
Gasoline
Gasoline is the result of distilling crude oil. This process breaks crude oil down into several components including tar, grease, refined oil, kerosene, diesel oil, gasoline, natural gas, and other light gasses. Gasoline is most commonly used in light trucks and passenger vehicles. Gasoline has a much higher flash point of approximately 495ºF. Gasoline engines require an ignition system to ignite the air fuel mixture. Ignition systems include spark plugs, ignition wires, distributor, and an ignition coils. Even though gasoline is not the most efficient type of engine they lead the industry because they are versatile, quite, and their tailpipe emissions or exhaust are cleaner than most.

11. Fuel & The four stroke engine
Comparing the Power Stroke of Diesel Vs. Gasoline
Fuel Injector
Spark Plug
DIESEL ENGINE
GASOLINE ENGINE
A fuel injector introduces fuel into the combustion chamber at the start of the power stroke.
The heat from generated from the previous stroke ignites the fuel forcing the piston downward.
The compressed fuel air mixture is ignited by a spark from the spark plug at the start of the power stroke forcing the piston downward.

12. Learning objective
The Four Stroke Cycle

13. The four stroke Cycle
CYCLE: A term that refers to the repetitive function of a mechanical system. The cycle is a function the is performed repeatedly.
Stroke: One linear motion of a piston from TDC to BDC or from BDC to TDC. There are 4 strokes for every cycle in an internal combustion engine.
TDC: Top Dead Center when the piston is at its absolute highest point of a given stroke.
BDC: Bottom Dead Center when the piston is at its absolute lowest point of a given stroke.

14. What Are The Four Strokes
The four stroke Cycle
What Are The Four Strokes
INTAKE
STROKE
COMPRESSION STROKE
POWER STROKE
EXHAUST STROKE
1ST
STROKE
2ND
STROKE
3RD
STROKE
4TH
STROKE

15. Air Fuel Mixture Is Drawn Into
The four stroke Cycle
Intake Stroke
First stroke of cycle
Piston moves from TDC to BDC
Intake valve open
Exhaust valve closed
On the intake stroke a precision mixture of fuel & air are drawn into the combustion chamber through the open intake valve. The Intake stroke may also be called the induction stroke.
Exhaust Valve Closed
Intake Valve Open
Air Fuel Mixture Is Drawn Into
Combustion Chamber
Crankshaft
Rotates
180º
Piston
Moves Downward

16. The four stroke Cycle Compression Stroke Second stroke of cycle
Piston moves from BDC to TDC
Intake & exhaust valves closed
On the compression stroke both valves remain closed while the piston is forced upward, as a result the air fuel mixture is squeezed or compressed preparing the mixture for ignition.
Exhaust Valve Closed
Intake Valve Closed
Air Fuel Mixture is Compressed
Piston Is Forced Upward
Acting on the Air Fuel Mixture
Crankshaft
Rotates
180º

17. Combustion Gases Expand Spark Plug Fires Igniting
The four stroke Cycle
Power Stroke
Third stroke of cycle
Piston moves from TDC to BDC
Intake & exhaust valves closed
Spark plug fires
The power stroke is the result of a process called ignition. When the spark plug fires the compressed fuel air mixture ignites. As the fuel air mixture ignites the gases begin to expand rapidly. Because the valves remain closed the gases push against the piston forcing it down.
Exhaust Valve Closed
Intake Valve Closed
Combustion Gases Expand
Spark Plug Fires Igniting
Air Fuel Mixture
Crankshaft
Rotates
180º
Piston
Is Forced Downward
When The
Expanding Combustion
Gases
Act On It

18. pushing against exhaust gasses
The four stroke Cycle
Exhaust Stroke
Fourth and final stroke of cycle
Piston moves from BDC to TDC
Intake valve closed
Exhaust Valve Open
During the exhaust stroke the piston travels upward forcing the spent exhaust gasses out of the combustion chamber through the open exhaust valve.
Exhaust Valve Open
Intake Valve Closed
Exhaust Gasses
Forced out
Piston forced upward
pushing against exhaust gasses
Crankshaft
Rotates
180º

19. The Four Stroke Process Animated
The four stroke Cycle
The Four Stroke Process Animated

20. Learning objective
Engine Components & Sub-Assemblies

21. Engine Components & Sub-Assemblies pushing against exhaust gasses
Engine Block
The Heart Of The Engine Assembly
Cylinder Bores
Coolant Passages
Oil Passages
The Engine Block is called the heart of the engine because all other components bolt to it. The block is the foundation for the entire engine assembly “The Engine Block contains the bearings that support the crankshaft and the cylinder…” bores where the pistons reciprocate. Some engine blocks house the camshaft. These are called pushrod type engines
Intake Valve Closed
Piston forced upward
pushing against exhaust gasses

22. Engine Components & Sub-Assemblies pushing against exhaust gasses
Crankshaft
Main bearing journals are supported by the engine block.
Connecting rod bearing journals support connecting rod . Connecting rod journals are offset from main journals
Counter weights use gravitational forces keep the crankshaft rotating on 1st, 2nd, & 4th strokes
The purpose of the crankshaft is to convert the reciprocating (Up & Down) motion of the piston and rod assembly into rotary (Circular) motion. Rotary motion is needed to drive the camshaft and the output shaft.
Intake Valve Closed
Piston forced upward
pushing against exhaust gasses

23. Engine Components & Sub-Assemblies pushing against exhaust gasses
Piston Assembly
Piston
Wristpin or Piston Pin
Connecting Rod
Connecting Rod Bearings
Connecting Rod Bearing End Caps
The Piston Assembly transfers the force of combustion from the piston through the connection rod to the crankshaft assembly.
Intake Valve Closed
Piston forced upward
pushing against exhaust gasses

24. Engine Components & Sub-Assemblies pushing against exhaust gasses
Camshaft Assembly
Timing Chain & Sprocket
Cam Bearings
Cam Bearing Journals
Cam Lobes
Distributor/Oil Pump Gear
The crankshaft drives the camshaft at ½ the speed of itself. This is because of the 2:1 cam to crank gear ratio. Force can be transferred to the camshaft via belt & pulley, chain & sprocket, or gear to gear. As the camshaft rotates it transmits valve signals through the valve train assembly to the intake & Exhaust valves to command them open upon the appropriate stroke.
Intake Valve Closed
Piston forced upward
pushing against exhaust gasses

25. Engine Components & Sub-Assemblies
Cylinder Head Assembly
Cast iron or cast aluminum
Cylinder heads contain spark plugs in gasoline engines and glow plugs in diesel engines
In Most engines the cylinder head contains most of the valve train assembly.
Cylinder heads are located at the top of the cylinder block and seal the combustion chamber on the 2nd and 3rd stroke. In many cases the cylinder may contain the camshaft these engines are called overhead Cam Design.
Intake Valve Closed
Piston forced upward
pushing against exhaust gasses

26. Engine Components & Sub-Assemblies pushing against exhaust gasses
Valve Train Assembly
Valve lifters or tappets
Pushrod
Rocker arm
Valve spring
Intake & Exhaust Valves
The Valve Train Assembly receives signals from the camshaft lobes to command open intake and exhaust valves on the appropriate strokes. Valves close when the valve springs return to their relaxed state.
Intake Valve Closed
Piston forced upward
pushing against exhaust gasses

27. Engine Components & Sub-Assemblies
Chevy 350 Small Block Exploded Diagram
Intake Valve Closed
Piston forced upward
pushing against exhaust gasses

28. Engine Components & Sub-Assemblies
Building A Complete Engine Assembly Animation
Intake Valve Closed
Piston forced upward
pushing against exhaust gasses