Engine Operation 4stroke
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UNI-KL MALAYSIA FRANCE INSTITUTE AUTOMOTIVE MAINTENANCE TECHNOLOGY SUBJECT: Engine Fundamental
TITLE: Engine Operation – Four stroke cycle
Four Stroke Gasoline Engine •
Engine provides the rotating power to drive the wheels through the transmission and driving axles. Automobile engines (gasoline and diesel) classified as internal combustion.
•
Its require air/fuel mixture enters into cylinder in correct time and compress it before spark plug ignite the air fuel mixture.
•
Reciprocating motion must be converted to a rotary motion before it can drive the wheels. This change is accomplished by connecting the piston to a crankshaft with a connecting rod. One end move up and down and the other end move in circle with crankshaft. Engine's power is transfer through the drive train to the wheels.
•
To allow the burnt air/fuel mixture out so a fresh mixture can enter and the engine can continue to run, engines are fitted with valves. At least two valves per cylinder, intake and exhaust. The valve will open and close by camshaft that driven by the crankshaft in specific ratio.
•
When the action of the valves and the spark plug is properly timed to the movement of the piston, the combustion cycle takes place in four strokes of the piston: the intake stroke, the compression stroke, the power stroke, and the exhaust stroke.
•
The up and down movement of the piston on all four strokes is converted to a rotary motion by the crankshaft. It takes two full revolutions of the crankshaft to complete the four stroke cycle.
•
Piston moves by the pressure produced during combustion only about half a stroke or one quarter of crankshaft revolution. This why a flywheel is needed to keep the pistons in motion during the rest of the four-stroke cycle and to compress the air/fuel mixture just before combustion.
INTAKE STROKE •
Piston move downward from TDC to BDC.
•
Intake valve opens.
•
These movements generate a partial vacuum in the cylinder.
•
It causes the atmospheric pressure to push air fuel mixture flow into cylinder through the open intake valve.
•
As the piston reaches BDC, the reduction in pressure stops.
•
Intake of air/fuel mixture slow down, but it’s not stop until the intake valve closes.
•
Intake valve closes after the piston has reached BDC.
•
This delayed closing of the valve increases the volumetric efficiency of the cylinder by packing as much air and fuel into it as possible.
UNI-KL MALAYSIA FRANCE INSTITUTE AUTOMOTIVE MAINTENANCE TECHNOLOGY SUBJECT: Engine Fundamental
TITLE: Engine Operation – Four stroke cycle
COMPRESSION STROKE • Piston move upward from BDC to TDC •
Both intake and exhaust valve are closed
•
Air fuel mixture trapped in the cylinder
•
Upward movements of the piston compress the air/fuel mixture and heat it up.
•
The volume of the cylinder with the piston at BDC compared to the volume of the cylinder with the piston at TDC determines the compression ratio of the engine.
POWER STROKE •
Piston move downward from TDC to BDC
•
Both intake and exhaust valve still closed
•
Several degree before piston reach TDC in compression stroke, spark plug ignites the compressed air fuel mixture
•
Burning fuel rapidly expands, creating a very high pressure against the top of the piston.
•
This drives the piston down toward BDC. The downward movement of the piston is transmitted through the connecting rod to the crankshaft.
EXHAUST STROKE • Piston move upward from BDC to TDC •
Intake valve still closed
•
Exhaust valve opens just before the piston reaches BDC on the power stroke
•
Pressure within the cylinder causes the exhaust gas to rush past the open valve and into the exhaust system.
•
Movement of the piston from BDC pushes most of the remaining exhaust gas from the cylinder.
•
As the piston nears TDC, the exhaust valve begins to close as the intake valve starts to open.
•
The exhaust stroke completes the four-stroke cycle
•
Opening of the intake valve begins the cycle again and this cycle occurs in each cylinder and is repeated over and over, as long as the engine is running.
UNI-KL MALAYSIA FRANCE INSTITUTE AUTOMOTIVE MAINTENANCE TECHNOLOGY SUBJECT: Engine Fundamental
TITLE: Engine Operation – Four stroke cycle
Four Stroke Diesel Engine •
Diesel Engine invented by Dr. Rudolph Diesel, a German engineer.
•
Used as power plant in heavy duty trucks, construction equipment, farm equipment, buses and marine applications.
•
During the late 1970s and early 1980s, many predicate small diesel engines would replace gasoline engines in passenger vehicles.
•
Diesel engines and gasoline engines share several similarities. They have a number of components in common, such as the crankshaft, pistons, valves, camshaft, water pump, oil pumps and they both are available in four stroke.
•
Diesel engine (compression-ignition engine) is easily recognized by the absence of an ignition system. Instead of relying on a spark for ignition, a diesel engine uses the heat produced by compressing air in the combustion chamber to ignite the fuel. The systems used in diesel powered vehicles are essentially the same as those used in gasoline vehicles.
•
Fuel injection is used on all diesel engines. Injectors spray pressurized fuel into the cylinders just as the piston is completing its compression stroke. The heat of the compressed air ignites the fuel.
•
Glow plug used to warm the precombustion chamber (indirect injection) when the engine is cold because without these plugs compression ratios cannot heat cold air enough to cause combustion.
•
Diesel combustion chambers are different from gasoline combustion chambers because diesel fuel bums differently.
•
Three types of combustion chambers are used in diesel engines 1.
Open combustion chamber (direct injection) - combustion chamber located' directly inside the piston. Diesel fuel is injected directly into the center of the chamber.
2.
Precombustion chamber (indirect injection) - second chamber connection to the main combustion chamber. On the power stroke, fuel is injected into the small chamber. Combustion is started there and then spreads to the main chamber. This design allows lower fuel injection pressures and simpler injection systems on diesel engines.
3.
Turbulence combustion chamber - designated to create an increase in air velocity or turbulence in the combustion chamber. The fuel is injected into the turbulent air and bums more completely
UNI-KL MALAYSIA FRANCE INSTITUTE AUTOMOTIVE MAINTENANCE TECHNOLOGY SUBJECT: Engine Fundamental
TITLE: Engine Operation – Four stroke cycle
OPERATION
Intake stroke •
Piston move downward from TDC to BDC.
•
Intake valve opens.
•
These movements generate a partial vacuum in the cylinder.
•
It causes the atmospheric pressure to push fresh air flow into cylinder through the open intake valve.
•
As the piston reaches BDC, the reduction in pressure stops.
•
Intake of fresh air slow down, but it’s not stop until the intake valve closes.
•
Intake valve closes after the piston has reached BDC.
•
This delayed closing of the valve increases the volumetric efficiency of the cylinder by packing as much air and fuel into it as possible.
Compression Stroke •
Piston move upward from BDC to TDC
•
Both intake and exhaust valve are closed
•
Fresh air trapped in the cylinder
•
Upward movements of the piston compress the fresh air and heat it up.
•
The volume of the cylinder with the piston at BDC compared to the volume of the cylinder with the piston at TDC determines the compression ratio of the engine.
UNI-KL MALAYSIA FRANCE INSTITUTE AUTOMOTIVE MAINTENANCE TECHNOLOGY SUBJECT: Engine Fundamental
TITLE: Engine Operation – Four stroke cycle
Power Stroke •
Piston move downward from TDC to BDC
•
Both intake and exhaust valve still closed
•
Several degree before piston reach TDC in compression stroke, fuel injector sprayed the diesel fuel and ignites the compressed fresh air
•
Burning fuel rapidly expands, creating a very high pressure against the top of the piston.
•
This drives the piston down toward BDC. The downward movement of the piston is transmitted through the connecting rod to the crankshaft.
Exhaust Stroke •
Piston move upward from BDC to TDC
•
Intake valve still closed
•
Exhaust valve opens just before the piston reaches BDC on the power stroke
•
Pressure within the cylinder causes the exhaust gas to rush past the open valve and into the exhaust system.
•
Movement of the piston from BDC pushes most of the remaining exhaust gas from the cylinder.
•
As the piston nears TDC, the exhaust valve begins to close as the intake valve starts to open.
•
The exhaust stroke completes the four-stroke cycle
•
Opening of the intake valve begins the cycle again and this cycle occurs in each cylinder and is repeated over and over, as long as the engine is running.
TITLE: Engine Operation – Four stroke cycle
Four Stroke Gasoline Engine •
Engine provides the rotating power to drive the wheels through the transmission and driving axles. Automobile engines (gasoline and diesel) classified as internal combustion.
•
Its require air/fuel mixture enters into cylinder in correct time and compress it before spark plug ignite the air fuel mixture.
•
Reciprocating motion must be converted to a rotary motion before it can drive the wheels. This change is accomplished by connecting the piston to a crankshaft with a connecting rod. One end move up and down and the other end move in circle with crankshaft. Engine's power is transfer through the drive train to the wheels.
•
To allow the burnt air/fuel mixture out so a fresh mixture can enter and the engine can continue to run, engines are fitted with valves. At least two valves per cylinder, intake and exhaust. The valve will open and close by camshaft that driven by the crankshaft in specific ratio.
•
When the action of the valves and the spark plug is properly timed to the movement of the piston, the combustion cycle takes place in four strokes of the piston: the intake stroke, the compression stroke, the power stroke, and the exhaust stroke.
•
The up and down movement of the piston on all four strokes is converted to a rotary motion by the crankshaft. It takes two full revolutions of the crankshaft to complete the four stroke cycle.
•
Piston moves by the pressure produced during combustion only about half a stroke or one quarter of crankshaft revolution. This why a flywheel is needed to keep the pistons in motion during the rest of the four-stroke cycle and to compress the air/fuel mixture just before combustion.
INTAKE STROKE •
Piston move downward from TDC to BDC.
•
Intake valve opens.
•
These movements generate a partial vacuum in the cylinder.
•
It causes the atmospheric pressure to push air fuel mixture flow into cylinder through the open intake valve.
•
As the piston reaches BDC, the reduction in pressure stops.
•
Intake of air/fuel mixture slow down, but it’s not stop until the intake valve closes.
•
Intake valve closes after the piston has reached BDC.
•
This delayed closing of the valve increases the volumetric efficiency of the cylinder by packing as much air and fuel into it as possible.
UNI-KL MALAYSIA FRANCE INSTITUTE AUTOMOTIVE MAINTENANCE TECHNOLOGY SUBJECT: Engine Fundamental
TITLE: Engine Operation – Four stroke cycle
COMPRESSION STROKE • Piston move upward from BDC to TDC •
Both intake and exhaust valve are closed
•
Air fuel mixture trapped in the cylinder
•
Upward movements of the piston compress the air/fuel mixture and heat it up.
•
The volume of the cylinder with the piston at BDC compared to the volume of the cylinder with the piston at TDC determines the compression ratio of the engine.
POWER STROKE •
Piston move downward from TDC to BDC
•
Both intake and exhaust valve still closed
•
Several degree before piston reach TDC in compression stroke, spark plug ignites the compressed air fuel mixture
•
Burning fuel rapidly expands, creating a very high pressure against the top of the piston.
•
This drives the piston down toward BDC. The downward movement of the piston is transmitted through the connecting rod to the crankshaft.
EXHAUST STROKE • Piston move upward from BDC to TDC •
Intake valve still closed
•
Exhaust valve opens just before the piston reaches BDC on the power stroke
•
Pressure within the cylinder causes the exhaust gas to rush past the open valve and into the exhaust system.
•
Movement of the piston from BDC pushes most of the remaining exhaust gas from the cylinder.
•
As the piston nears TDC, the exhaust valve begins to close as the intake valve starts to open.
•
The exhaust stroke completes the four-stroke cycle
•
Opening of the intake valve begins the cycle again and this cycle occurs in each cylinder and is repeated over and over, as long as the engine is running.
UNI-KL MALAYSIA FRANCE INSTITUTE AUTOMOTIVE MAINTENANCE TECHNOLOGY SUBJECT: Engine Fundamental
TITLE: Engine Operation – Four stroke cycle
Four Stroke Diesel Engine •
Diesel Engine invented by Dr. Rudolph Diesel, a German engineer.
•
Used as power plant in heavy duty trucks, construction equipment, farm equipment, buses and marine applications.
•
During the late 1970s and early 1980s, many predicate small diesel engines would replace gasoline engines in passenger vehicles.
•
Diesel engines and gasoline engines share several similarities. They have a number of components in common, such as the crankshaft, pistons, valves, camshaft, water pump, oil pumps and they both are available in four stroke.
•
Diesel engine (compression-ignition engine) is easily recognized by the absence of an ignition system. Instead of relying on a spark for ignition, a diesel engine uses the heat produced by compressing air in the combustion chamber to ignite the fuel. The systems used in diesel powered vehicles are essentially the same as those used in gasoline vehicles.
•
Fuel injection is used on all diesel engines. Injectors spray pressurized fuel into the cylinders just as the piston is completing its compression stroke. The heat of the compressed air ignites the fuel.
•
Glow plug used to warm the precombustion chamber (indirect injection) when the engine is cold because without these plugs compression ratios cannot heat cold air enough to cause combustion.
•
Diesel combustion chambers are different from gasoline combustion chambers because diesel fuel bums differently.
•
Three types of combustion chambers are used in diesel engines 1.
Open combustion chamber (direct injection) - combustion chamber located' directly inside the piston. Diesel fuel is injected directly into the center of the chamber.
2.
Precombustion chamber (indirect injection) - second chamber connection to the main combustion chamber. On the power stroke, fuel is injected into the small chamber. Combustion is started there and then spreads to the main chamber. This design allows lower fuel injection pressures and simpler injection systems on diesel engines.
3.
Turbulence combustion chamber - designated to create an increase in air velocity or turbulence in the combustion chamber. The fuel is injected into the turbulent air and bums more completely
UNI-KL MALAYSIA FRANCE INSTITUTE AUTOMOTIVE MAINTENANCE TECHNOLOGY SUBJECT: Engine Fundamental
TITLE: Engine Operation – Four stroke cycle
OPERATION
Intake stroke •
Piston move downward from TDC to BDC.
•
Intake valve opens.
•
These movements generate a partial vacuum in the cylinder.
•
It causes the atmospheric pressure to push fresh air flow into cylinder through the open intake valve.
•
As the piston reaches BDC, the reduction in pressure stops.
•
Intake of fresh air slow down, but it’s not stop until the intake valve closes.
•
Intake valve closes after the piston has reached BDC.
•
This delayed closing of the valve increases the volumetric efficiency of the cylinder by packing as much air and fuel into it as possible.
Compression Stroke •
Piston move upward from BDC to TDC
•
Both intake and exhaust valve are closed
•
Fresh air trapped in the cylinder
•
Upward movements of the piston compress the fresh air and heat it up.
•
The volume of the cylinder with the piston at BDC compared to the volume of the cylinder with the piston at TDC determines the compression ratio of the engine.
UNI-KL MALAYSIA FRANCE INSTITUTE AUTOMOTIVE MAINTENANCE TECHNOLOGY SUBJECT: Engine Fundamental
TITLE: Engine Operation – Four stroke cycle
Power Stroke •
Piston move downward from TDC to BDC
•
Both intake and exhaust valve still closed
•
Several degree before piston reach TDC in compression stroke, fuel injector sprayed the diesel fuel and ignites the compressed fresh air
•
Burning fuel rapidly expands, creating a very high pressure against the top of the piston.
•
This drives the piston down toward BDC. The downward movement of the piston is transmitted through the connecting rod to the crankshaft.
Exhaust Stroke •
Piston move upward from BDC to TDC
•
Intake valve still closed
•
Exhaust valve opens just before the piston reaches BDC on the power stroke
•
Pressure within the cylinder causes the exhaust gas to rush past the open valve and into the exhaust system.
•
Movement of the piston from BDC pushes most of the remaining exhaust gas from the cylinder.
•
As the piston nears TDC, the exhaust valve begins to close as the intake valve starts to open.
•
The exhaust stroke completes the four-stroke cycle
•
Opening of the intake valve begins the cycle again and this cycle occurs in each cylinder and is repeated over and over, as long as the engine is running.
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