What are the 2 types of diesel engines?

While there are multiple ways to categorize diesel engines, two fundamental distinctions are commonly used:

1. Based on the number of strokes they complete per cycle:

  • Four-stroke diesel engines: This is the most common type, used in the vast majority of trucks, cars, and other applications. These engines complete the combustion process in four distinct strokes:
    • Intake stroke: Air is drawn into the cylinder.
    • Compression stroke: The air is compressed, raising its temperature.
    • Combustion stroke: Fuel is injected, ignites spontaneously due to the heat, and pushes the piston down.
    • Exhaust stroke: Burned gases are expelled from the cylinder.
  • Two-stroke diesel engines: These are less common and primarily used in smaller applications like generators and lawnmowers. They complete the entire combustion process in just two strokes:
    • Intake/compression stroke: Air is drawn in, the piston compresses the air, and fuel is injected.
    • Combustion/exhaust stroke: The fuel ignites, pushing the piston down, and then the exhaust gases are expelled.

2. Based on their fuel injection system:

  • Indirect injection (IDI) diesel engines: In these engines, fuel is injected into a pre-combustion chamber where it mixes with air and ignites. This design is generally used in older engines or smaller engines with lower power requirements.
  • Direct injection (DI) diesel engines: With DI engines, fuel is injected directly into the main combustion chamber. This allows for more precise control over the combustion process, leading to better efficiency, performance, and lower emissions compared to IDI engines.
    • Common rail direct injection (CRDI) diesel engines: This is a specific type of DI engine where the fuel is stored in a common rail at high pressure and then injected into each cylinder individually. CRDI engines offer even greater control and precision compared to standard DI engines, resulting in further improvements in efficiency, performance, and emissions.

It’s important to note that these categorizations are not mutually exclusive. For example, a four-stroke diesel engine can be either an IDI or a DI engine. The specific type of engine used in a particular application will depend on various factors such as power requirements, emissions regulations, and cost considerations.