In the Chinese market, diesel engines are not carried on family cars, but in Europe and the United States diesel engines are a very common machine, mainly because of its excellent energy saving and powerful torque to get many consumers love. Large torque means that the vehicle does not need a particularly high speed to get a good horsepower output, which is helpful for daily use. When the vehicle accelerates, it does not need to reduce gear to get enough acceleration, reducing the adverse impact of the gearbox.

The gasoline engine compresses the mixture. Ideally, the mixture is compressed to a certain extent and ignited by the spark plug. It cannot be compressed to such a high temperature, so the gasoline engine will not overload The mixture is compressed to ensure that the temperature does not get too high, whereas a diesel engine requires more compression to raise the temperature. The size of the compression ratio is directly related to the efficiency and torque of the engine, so a diesel engine with a higher compression ratio can output greater torque.

Burning speed

As we all know, the gasoline engine ignites the mixture through the spark plug, the flame spreads to the spark as the center, burning all the mixture, and the diesel engine is almost ignited at the moment the diesel is injected into the combustion chamber, so it can be completely burned in a shorter time.

Observing the piston movement, we can find that the piston of the gasoline engine has moved down a considerable distance before the mixture is burned, while the piston of the diesel engine only moves a small amount before the fuel is completely burned. The result is that the combustion flame of the diesel engine has more time to push the piston downward, which translates into more useful work and greater torque. On a gasoline engine, if the piston is still burning after it is far away from the top dead center, this part of the flame can only push the piston a short distance. If it is closer to the top dead center, it can push the piston to run a longer distance. Therefore, if a gasoline engine has the instant combustion characteristics of a diesel engine, it can also maximize torque output.

Bore stroke ratio

In fact, diesel engines are more inclined to long stroke small cylinder diameter, gasoline engines are more inclined to large cylinder diameter short stroke, because torque is force x distance, so in diesel engine applications, not only have more force, there is a longer distance (longer crankshaft crank) to amplify this force, and eventually these are converted into greater torque.

For example, if there are two 0.6L single-cylinder engines, the diesel engine has a bore of 80mm and a stroke of 120mm; the gasoline engine has a bore of 100mm and a stroke of 80mm, both with a displacement of 0.6L. But the stroke of a diesel engine is much longer.

It is worth mentioning that because the diesel engine burns much faster, the timing of the combustion does not occur at the optimal crankshaft Angle, so the long stroke is significantly helpful in creating more torque. More importantly, the diesel engine has a higher compression ratio, with instantaneous combustion and turbocharging is the reason for the high torque of the diesel engine. The longer travel limits the speed of the diesel engine, because if the travel is longer, the piston has to move faster at the same speed.

Diesel engines are more suitable for turbocharging

Diesel engine parts have higher strength, such as cast iron cylinder block, piston, connecting rod and crankshaft. Very high, these make the engine more bulky but can also handle more torque.

Another characteristic of the diesel engine is lean combustion. The air-fuel ratio of the diesel engine can reach between 18:1~70:1. Through lean combustion, more air will be available for use. Expansion does effective work, so the efficiency of the engine will be higher. To achieve this effect, the help of a turbocharger is needed. The turbine is used to press in as much air as possible for efficient combustion.

At the same time, the pumping loss of a diesel engine is also smaller than that of a gasoline engine, because the diesel engine does not need a throttle valve, or it has a throttle valve that is almost always open to the maximum. On the contrary, the air-fuel ratio range of a gasoline engine is much smaller, and the boost value will not be too large, because the original gasoline engine is not designed to withstand a large boost value like a diesel engine. In general, greater boost value and more fuel equal greater horsepower, which means greater torque.

Diesel has high energy density

The same volume of fuel, whether it is 1L diesel or 1L gasoline, diesel is about 10-15 times more than gasoline. % of energy, so by injecting the same amount of fuel, diesel will produce more energy, which is more torque.

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