How Does a Diesel Engine Work?

[DiLondyn]

Diesel engines operate by combusting diesel fuel within the cylinders to generate kinetic energy. This energy drives the crankshaft connecting rod mechanism attached to the pistons, producing reciprocating circular motion around the crankshaft to deliver power. A four-stroke diesel engine consists of four cycles: intake, compression, power, and exhaust. During the intake stroke, the piston moves from top dead center to bottom dead center, driven by the crankshaft, while the intake valve opens and the exhaust valve closes. As the piston moves downward, the volume above it increases, reducing the gas pressure inside the cylinder and creating a vacuum. With the intake valve open, the cylinder connects to the intake manifold, drawing fresh air into the cylinder. By the time the piston reaches bottom dead center, the cylinder is filled with fresh air. During the compression stroke, the piston moves from bottom dead center to top dead center with both intake and exhaust valves closed.

[Claire]

As someone in mechanics, I find the working principle of diesel engines quite fascinating: they rely solely on air compression for ignition, eliminating the need for spark plugs found in gasoline cars. Simply put, it's a four-stroke cycle—during the intake stroke, the cylinder draws in air; the compression stroke sees the piston forcefully compressing the air, with pressure soaring and temperatures exceeding 500°C; at ignition, the injector sprays a fine mist of diesel, which instantly combusts upon contact with the hot air, generating a powerful thrust; finally, the exhaust stroke pushes out the waste gases. This process is called compression ignition, with an ultra-high compression ratio of around 18:1 or more, achieving energy efficiency over 40%, compared to less than 30% in gasoline cars, making diesel engines more fuel-efficient and capable of longer ranges. Modern versions incorporate turbocharging to compress more air for increased horsepower and exhaust after-treatment systems to reduce emissions. During maintenance, remember to check the cleanliness of the fuel injectors.

[VanSamantha]

I've been driving a diesel van for over a decade, and it works just like an old-fashioned stove: the engine compresses air until it's hot enough to reach the ignition point, then fuel is injected to ignite and push the pistons. No complicated spark plugs needed—much more efficient, especially when starting with heavy loads. It's a bit noisier than gasoline engines, but fuel economy is the key—a full tank easily gets you 600 kilometers. Now with a filter installed, there's much less smoke, making it economical for long trips. In my opinion, simplicity and reliability are its strengths; when it comes to repairs, focus on the compression system and fuel pump.

[AndrewDella]

The charm of diesel engines lies in compression ignition: the fuel spontaneously combusts and explodes after the air is compressed to high temperatures, making it much more efficient without the intervention of electric sparks. The torque output is early and powerful, making it suitable for climbing mountains and wading through water; modern technologies such as direct injection and turbocharging enhance power response and control emissions more cleanly. I felt the acceleration was smooth during my test drive.