Lesson Notes By Weeks and Term v4 - SHS 2
INTRODUCTION TO ENGINE TECHNOLOGY
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INTRODUCTION TO ENGINE TECHNOLOGY
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Subject: Applied Technology
Class: SHS 2
Term: 1st Term
Week: 1
Grade code: 2.1.1.LI.3
Strand code: 1
Sub-strand code: 1
Content standard code: 2.1.1.CS.1
Indicator code: 2.1.1.LI.3
Theme: AUTOMOTIVE TECHNOLOGY
Subtheme: INTRODUCTION TO ENGINE TECHNOLOGY
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The internal combustion engine, found in most cars, 'troskis', and trucks we see on Ghanaian roads from Accra to Bolgatanga, generates an immense amount of heat. If this heat is not controlled, the engine will quickly overheat, get damaged, and leave the vehicle stranded. This lesson explores the brilliant system designed to keep the engine at its perfect operating temperature: the pressurized water-cooling system. Understanding this system is crucial for anyone who wants to drive, maintain, or repair a vehicle, helping to prevent costly breakdowns and ensure safety on our roads.
A. The Purpose of the Engine Cooling System An engine produces power by burning fuel (petrol/diesel) in a series of controlled explosions. This process creates extremely high temperatures (over 2000°C) inside the cylinders. Problem: If left uncontrolled, this heat would cause the engine's metal parts to expand, warp, or even melt. The engine oil would break down and stop lubricating properly. This leads to catastrophic engine failure. Solution: The cooling system's job is not to make the engine cold, but to keep it at its most efficient operating temperature (typically between 85°C and 105°C). B. The Pressurized Water-Cooling System: Components and Operation
This is the most common type of cooling system in modern vehicles. It circulates a special liquid called coolant through the engine to absorb heat and then dissipates that heat into the air.
Key Components: Radiator: A large heat exchanger, usually at the front of the car. It has many thin tubes and fins that allow air to pass through and cool the hot coolant flowing inside. Coolant (or "Water"): A mixture of distilled water and antifreeze/anti-corrosion chemicals. It absorbs heat well and prevents rust inside the engine. Water Pump: A belt-driven pump that continuously circulates the coolant through the system. Radiator Fan: Pulls air through the radiator, especially when the car is moving slowly or stopped in traffic (like in a 'go-slow' in Kaneshie). It can be driven by the engine belt or an electric motor. Hoses: Flexible rubber tubes that connect the components and carry the coolant. Thermostat: A temperature-sensitive valve that controls the flow of coolant to the radiator. (We will study this in detail). Radiator Pressure Cap: A special cap that seals the system and allows it to build pressure. (We will also study this in detail). Coolant Passages (Water Jackets): Channels built into the engine block and cylinder head that allow coolant to flow around the hot parts.
How it Works (The Coolant's Journey): Cold Engine: When you first start the car, the thermostat is closed. The water pump circulates coolant only within the engine block and cylinder head (through a bypass hose). This allows the engine to warm up quickly to its efficient operating temperature. A cold engine is inefficient and produces more pollution. Hot Engine: As the engine reaches its operating temperature (e.g., 90°C), the thermostat opens. The water pump now pushes hot coolant from the engine, through the top hose, into the radiator. As the coolant flows down through the radiator tubes, the fan and the airflow from the moving car remove heat from it. The cooled liquid collects at the bottom of the radiator. The water pump pulls this cooled coolant from the radiator's bottom hose and sends it back into the engine to absorb more heat. This cycle repeats continuously to maintain the correct temperature.