How Diesel Engines Differ From Gasoline Engines

Initially, it may seem that the difference between gasoline engines and diesel engines is the fuel. The differences, however, go beyond fuel and into the inner workings of the engines themselves. Both gasoline and diesel engines are internal combustion engines that turn fuel into mechanical energy. This energy is created by small explosions that move pistons up and down, which in turn rotates the wheels via the crankshaft. The difference between diesel and gasoline engines is how these small explosions are created. This difference creates varying levels of power.

Internal combustion engines work on the principle of pistons and strokes. Pistons are worked up and down by the combustion of fuel in the cylinder, which pushes the piston down. The end of the piston is connected to a crankshaft, which translates the linear energy to rotational energy. This energy is then transferred to the transmission, which turns the wheels and provides the torque that is needed to drive faster, go uphill, drive through snow, etc.

The strokes are the vertical movements of the piston. Most gasoline and diesel engines work in four strokes. The first stroke goes down and pulls air into the chamber, and the second stroke goes up and compresses the air. As the second stroke hits the top, it prompts a small explosion, and the piston is pushed down into the third stroke. The fourth stroke pushes the exhaust that is created by the combustion out through the exhaust valve, and the whole process starts over with the intake of fresh air. Both gasoline and diesel engines work in this way. The difference is in how the combustion occurs.

Diesel engines ignite fuel by compressing air. Compressed air is higher in temperature than non-compressed air and is enough to ignite the fuel. Gasoline engines inject fuel and air at the same time, using spark plugs, which diesel engines usually do not have. In gasoline engines, compressed air is injected into the cylinder and further compressed by the second stroke of the piston. The fuel is then injected, and combustion occurs as the fuel comes in contact with warmer air. Diesel engines require different fuel because gasoline is highly flammable and compressed air would ignite the gasoline before the top of the second stroke. The energy from the combustion would push the piston down as it was on its way up, and the force might destroy the engine.

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