Introduction of four-stock engine and its contains about How the Four-Stroke Engine Works, Key Components, Advantages, Disadvantages, Otto Cycle

 

A "four-stock engine" seems to be a typo or misunderstanding — the correct term is likely a "four-stroke engine." Here's a quick explanation:

What is a Four-Stroke Engine?

A four-stroke engine is an internal combustion engine that completes a power cycle in four strokes of the piston:

1. Intake Stroke: The intake valve opens, and the piston moves down, drawing in an air-fuel mixture.

2. Compression Stroke: The piston moves up with valves closed, compressing the mixture.

3. Power Stroke: The spark plug ignites the mixture, and the explosion pushes the piston down — this is where power is generated.

4. Exhaust Stroke: The exhaust valve opens, and the piston moves up again, expelling exhaust gases.

 

These engines are common in cars, motorcycles, and lawn equipment.

How the Four-Stroke Engine Works (Detailed)

1. Intake Stroke

• Action: Piston moves down.

• Valves: Intake valve opens, exhaust valve stays closed.

• What Happens: Air-fuel mixture enters the combustion chamber from the carburetor or fuel injector.

2. Compression Stroke

• Action: Piston moves up.

• Valves: Both valves are closed.

• What Happens: Mixture is compressed, increasing its potential energy.

3. Power Stroke (Combustion)

• Action: Piston is forced down by the explosion.

• Valves: Remain closed.

• What Happens: A spark (from the spark plug) ignites the compressed mixture. This explosion generates power to drive the crankshaft.

4. Exhaust Stroke

• Action: Piston moves up again.

• Valves: Exhaust valve opens, intake valve stays closed.

• What Happens: Burnt gases are expelled from the chamber through the exhaust valve.

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Key Components of a Four-Stroke Engine

• Piston

• Cylinder

• Crankshaft

• Camshaft

• Valves (Intake and Exhaust)

• Spark Plug

• Connecting Rod

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Advantages of Four-Stroke Engines

• Fuel Efficiency: Better than two-stroke engines.

• Durability: Longer life due to less wear.

• Lower Emissions: Cleaner combustion.

• More Torque: Especially at low speeds.
  

Disadvantages

• More Complex: More parts, like valves and camshafts.

• Heavier: Not ideal for lightweight equipment.

• More Expensive to manufacture and maintain.

   

  Four-Stroke Engine – Advanced Overview

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  1. Cycle Timing and Crankshaft Movement

  Each stroke happens over 180° of crankshaft rotation, so the full cycle takes 720° (2 full revolutions):

• Intake: 0–180°

• Compression: 180–360°

• Power: 360–540°

• Exhaust: 540–720°

This means power is produced once every two revolutions, which is why four-stroke engines have smoother, more controlled power delivery compared to two-strokes.

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 Valve Timing and Overlap

Modern engines use camshafts to open and close valves in sync with piston movement. Timing can be:

• Fixed (older engines)

• Variable Valve Timing (VVT) — used in modern cars to optimize performance and fuel economy at different RPMs (e.g., Honda VTEC, Toyota VVT-i)

Valve Overlap

A brief period when both intake and exhaust valves are open—used to improve exhaust scavenging and airflow at higher RPMs.

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 Thermodynamics Behind the Engine (Otto Cycle)

Four-stroke petrol engines operate on the Otto Cycle:

1. Isentropic Compression (Compression Stroke)

2. Constant Volume Heat Addition (Spark Ignition)

3. Isentropic Expansion (Power Stroke)

4. Constant Volume Heat Rejection (Exhaust Stroke)

This model helps engineers analyze efficiency and heat loss.

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 Types of Four-Stroke Engines (Based on Application)

Type	Used In	Notes
Single-cylinder	Motorcycles, generators	Simple and lightweight
Inline-4	Most cars, small trucks	Common, good balance of power and cost
V6, V8, V12	Performance/sports cars	More power, smoother operation
Boxer (Flat)	Subaru, Porsche	Low center of gravity
Diesel Four-Strokes	Trucks, trains, ships	Higher compression, no spark plugs

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Real-World Applications

• Cars: Virtually all standard gasoline-powered cars use four-stroke engines.

• Motorcycles: Both two- and four-stroke, but four-stroke is more common in street bikes.

• Lawn Equipment: Four-stroke is gaining popularity for lower emissions.

• Aircraft (piston): Certified aircraft often use air-cooled four-stroke engines.

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Innovations in Four-Stroke Engines

• Turbocharging / Supercharging: Increases power output by forcing more air into the cylinder.

• Hybrid Assist: Combines four-stroke ICEs with electric motors (Toyota Prius).

• Direct Injection: Fuel is injected directly into the cylinder, improving combustion.

• Cylinder Deactivation: Temporarily shuts off cylinders under low load for better fuel economy.

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