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Internal Combustion Engines
With an internal combustion engine, fuel is burned inside the engine in what is known as a combustion chamber. The combustion chamber is an enclosed space where the gasoline goes. Once the gas of the confined gasoline expands, it produces energy.
The more compressed the mixture of air and fuel, the greater the risk of it bursting into flames. This is why high octane gasoline is recommended for high performance cars. Although it may cost a bit more, it prevents the higher compression of these engines from premature combustion.
The Four-Stroke Combustion Cycle
Although you can find two-stroke combustion cycles in some boat and motorcycle engines, as well as snowmobile and personal watercraft engines, most internal combustion engines found in today's cars use the four-stroke combustion cycle. This cycle turns fuel into motion, i.e., it makes your car go.
Very simply put, the first stroke intakes fuel; the second compresses the fuel; the third combusts the fuel; and the fourth exhausts the fuel.
The four-stroke combustion cycle's advantages over the two-stroke combustion cycle are the fuel efficiency and cleanliness―two very attractive qualities in today's world of ever-increasing gas prices and air pollution.
The Four-Stroke Engine
Knowing the parts of a four-stroke engine will help you understand how an internal combustion engine works.
Your basic four-stroke engine is going to include the following parts:
- Crankshaft, which sets the linear piston into rotation.
- Camshaft(s), which open the valves once every two times the crankshaft rotates.
- Valves, or poppet valves, which control the flow of fuel.
- Cylinder(s), which is where the piston travels.
- Spark plug(s), which ignite the compressed fuel. There is one spark plug for every cylinder.
- Piston, which exerts force on the fuel inside the cylinder(s).
- Crank, which is the bent part of the shaft that changes motion from reciprocating (back and forth or up and down) to circular, or vice versa. This motion leads to pushing the piston down, pushing the crankshaft round, and setting the wheels of the vehicle in motion.
Summary
If the majority, or all, of your experience with vehicles has been behind the wheel and not under the hood, much of this probably sounds foreign to you. Let's recap.
Take another look at the description of the four-stroke combustion cycle.
During the first stroke of the cycle―the intake stroke―the intake of fuel occurs. This means that your vehicle's fuel, most often gasoline, fills up the combustion chamber.
Once the fuel is in the combustion chamber,―the compression stroke―compresses the fuel. This is to prepare it for ignition since fuel will ignite easier when pressurized.
Now that the fuel is compressed, the spark plugs will ignite the fuel, similar to a tiny explosion, during ―the combustion stroke.
During the exhaust stroke, the fumes of the burned fuel are pushed out into the exhaust system.
There are a number of pistons inside an engine depending on the design, 4 to 12 cylinders usually. The pistons are connected to a crankshaft through a connecting rod. Pistons fire consecutively to rotate the crankshaft inside the engine block . The oil pump pushes oil through the oil filter and then supplies oil to vital engine parts including the crank and camshaft, cylinder walls and piston rings, valve train, cam lifters and the timing gears or chain. Motor oil is used to lubricate and cool internal engine parts. Oil is pumped up through the engine, then returns to the bottom of the engine .
The cylinder head is connected to the top of the engine block and allows air/fuel mixture and exhaust into and out of the cylinder block. The cylinder head has the duty of holding the air/fuel mixture charge inside the cylinder as it combusts, forcing the piston downward. The cylinder head is connected to the engine block using head bolts, using a head gasket to seal both parts.
Over Head Cam Cylinder Head
A camshaft is used to open and close intake and exhaust ports by using valve train components. These components will vary depending on the design of the engine. There are primarily two styles of valve systems: over head cam which consists of acamshaft and lifter, and the in block system which consist of a camshaft , lifter, push rod, rocker arm. Both styles utilize a valve spring to hold the valve closed.
There are four main sections to the internal combustion engine.
1. Engine Block: (short block) note: a long block includes cylinder heads.
a. main engine block
b. crankshaft
c. pistons
d. piston rings
e. connecting rod pin
f. connecting rod
g. camshaft (in over head valve engines)
h. lifters (in over head valve engines)
i. oil pump
j. oil pump drive
k. oil pump pick up
l. gaskets and seals
m. freeze plugs
n. oil pan
o. assorted bolts
2. cylinder heads
a. main head cylinder body
b. intake and exhaust valves
c. valve keepers
d. valve spring
e. valve spring retainer
f. valve stem seal
3. Air/fuel intake system
a. intake manifold
b. fuel injectors
c. fuel injection system
d. air filter
4. Exhaust system
a. exhaust manifold
b. catalytic converter
c. muffler
Proper maintenance is crucial to optimum performance for every internal combustion engine. Follow your manufacturer recommended service schedules protect yourself by service your vehicle regularly.
Common Problems:
- Neglected regular maintenance resulting in premature engine failure
- cooling system neglect causing overheating resulting in premature engine failure