Lesson Notes By Weeks and Term v4 - SHS 1

Lesson Video

This page supports the lesson note with a companion video and a short classroom-ready summary.

For class groups and homework, share this lesson page so learners also get the summary, objectives, and full lesson context.

Performance objectives

• Identify the main components of petrol and diesel engines.
• Explain the operational differences between them.
• Compare the construction of spark ignition and compression ignition engines.
• Understand the pros and cons of each engine type in Ghana.

Lesson summary

Welcome, future technicians and engineers! Almost every day in Ghana, we see cars, tro-tros, buses, and trucks moving people and goods. Have you ever wondered why a big cargo truck sounds so different from a small taxi? Or why they use different fuels at the filling station? The answer lies in the "heart" of the vehicle: the engine. Today, we will explore the two most common types of engines—petrol and diesel—to understand how they are built and how they work differently. This knowledge is the foundation for anyone who wants to understand, repair, or even design the vehicles that power our country.

Lesson notes

A. Introduction to the Internal Combustion Engine (ICE)

Both petrol and diesel engines are types of Internal Combustion Engines (ICE). Internal: This means the fuel is burned *inside* the engine itself (in a cylinder). Combustion: This is the rapid burning of fuel, which creates a high-pressure gas that pushes a piston down. Engine: A machine that converts this chemical energy (from burning fuel) into mechanical energy (to turn the wheels).

The goal of both engines is the same: to create a controlled explosion that pushes a piston. However, *how* they achieve this explosion is very different. Petrol Engine: Also known as a Spark Ignition (SI) Engine. It uses a spark plug to ignite a pre-mixed air-fuel mixture. Diesel Engine: Also known as a Compression Ignition (CI) Engine. It compresses air until it becomes extremely hot, and then injects fuel, which ignites instantly from the heat. B. Key Constructional Differences

Let's look at the physical parts that make these engines different. Imagine we have two engine blocks side-by-side, one from a Toyota Corolla (petrol) and one from a Ford Ranger (diesel).

Evaluation guide

• Explain the constructional and operational differences between petrol and
• diesel engines
• Problem based Learning: Display a dismantled engine for the learners to identify
• the various components and their precise positions in the spark ignition (SI) and

Reference guide

• :
• Whiteboard/Chalkboard and markers/chalk.
• Charts or large diagrams showing a cross-section of a petrol engine and a diesel engine.
• (If available, as suggested by NaCCA exemplar) A dismantled engine block, a spark plug, a fuel injector, a piston.
• Video clips showing the four-stroke cycle for both engine types (optional, can be shown via a projector/laptop).
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