For merchants engaged in the supply of engine parts, lubricants, fuel systems, or auto parts, understanding the working principle of gasoline engines is not exclusive to technicians, but a basic skill to make good product recommendations and enhance customer trust. Whether you are a supplier of injectors, spark plugs, or a complete set of ignition system parts, understanding how this "internal combustion heart" works will determine whether you can really "speak" in front of customers.
Below, we will use popular and natural language to talk about the core working principle of gasoline engines, which is particularly suitable for suppliers to quickly establish a knowledge framework.
Four-stroke cycle: the basic rhythm of the engine
Most gasoline engines use a four-stroke working cycle, which is the four steps of "intake-compression-work-exhaust". For each complete cycle, the engine's piston will reciprocate twice and the crankshaft will rotate twice before it can output power once.
The first step is intake.
The intake valve opens, the piston moves downward, and the atmospheric pressure draws air (or combustible gas mixed with gasoline) into the cylinder.
The second step is compression.
The intake valve is closed, the piston moves upward, compressing the inhaled mixture, and the temperature and pressure rise synchronously.
The third step is to do work.
When the piston approaches the top dead center, the spark plug ignites the mixture, and the intense combustion produces high-temperature and high-pressure gas, which pushes the piston downward to complete the energy output.
The fourth step is exhaust.
The exhaust valve opens, and the piston moves upward again, pushing the burned exhaust gas out of the cylinder to prepare for the next cycle.
These four steps seem simple, but they are the "metronome" of the engine's continuous operation, and all power output and efficiency performance are determined by this.
Ignition system and fuel supply system: the "right and left hands" of gasoline engines
The biggest feature of gasoline engines is ignition combustion, that is, it does not rely on the temperature of compressed gas to spontaneously ignite, but relies on spark plugs to actively ignite.
Therefore, the ignition system has become the key nerve of the engine. It consists of spark plugs, ignition coils, distributors (or electronic control modules), etc., and is responsible for accurately releasing high-voltage electric sparks at the end of the compression stroke to ignite the mixture.
To ignite, there must be a precise fuel supply. This is inseparable from the coordination of the fuel supply system. Most modern gasoline engines use electronic injection technology, where the fuel injector atomizes the gasoline and mixes it with air in proportion to form a suitable air-fuel ratio.
From the supplier's perspective, the components involved in these two systems are particularly critical. Spark plugs, ignition coils, fuel injectors, fuel pumps, etc., are the basis for stable operation. If you are supplying these accessories, you must know their role and importance in the engine cycle.
Key differences from diesel engines: compression ignition vs. ignition
Many customers often ask: What is the difference between gasoline engines and diesel engines? The core difference lies in the combustion method.
Gasoline engines use ignition combustion, and spark plugs are required to ignite the mixture of air and gasoline.
Diesel engines use compression ignition combustion, relying on high-pressure compressed air to reach extremely high temperatures, and then injecting diesel to ignite itself, without the need for spark plugs.
In addition, diesel engines usually have a higher compression ratio, high torque but low speed, while gasoline engines have fast response, high speed, and smoother operation. These differences also determine their differences in vehicle use, engine structure, and accessories.
