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Why Are Big Vehicles Typically Fitted with Diesel Engines

Why Are Big Vehicles Typically Fitted with Diesel Engines

When you decide to buy a car, you commonly have the option between a diesel and a gasoline engine. Lately, there have been hybrid and electric options as well, but they still comprise a fractionally small market in the world.

However, if you want to buy a big vehicle, like a bus or a truck, or even a boat, you are almost exclusively limited to diesel engines. Have you ever wondered why? Diesel engines are very durable and energy-efficient, and engine manufacturers guarantee for them for a long time, like the Cummins warranty that they give for all their engines.

The Purpose of the Vehicle

The main factor the vehicle manufacturers use to choose between the diesel and the gasoline engine is the purpose of the vehicle. Larger vehicles tend to be heavier as well as carry much more load. That means that you will need a larger or stronger engine.

However, if you look at the specifications of comparable diesel and gasoline engines, the numbers are not always on the side of the diesel engine. So, what is the catch?

Torque Matters

The secret of the diesel engine is the torque, or the moment of force. In essence, it determines how well the power of the engine is transferred to the wheels. This allows the vehicle to accelerate. Diesel engines almost invariantly have much larger torque than comparable gasoline engines.

More importantly, diesel engines are capable of achieving huge amounts of torque at low revs. This is particularly important to trucks and farm machinery like tractors. They don’t need to gain much speed fast, but they do need a lot of moving capability fast. That is why diesel engines are designed differently than gasoline engines.

How Is Greater Torque Achieved?

More torque is generated by the offset of the crankshaft. This offset is a lot bigger in the diesel engine, which enables the engine to have a longer stroke. With the longer stroke also comes much greater compression of the ignition.

However, the crankshaft is not the only thing that gives the diesel the well-known torque. It also comes from the way it controls the power output. Unlike a gasoline engine with throttle plates, a diesel engine controls the power by the amount of fuel which is fed to the engine. If you idle a diesel engine, it will hardly consume any fuel.

What that means is that you can get a lot of power just by adding a lot of fuel, regardless of your speed and RPMs. However, that does come with a drawback of having very limited RPMs in every gear, since the maximum torque is achieved at low RPMs. That explains the multitude of gears in trucks and tractors.

If Given the Choice, What Should I Get?

To put it as simply as possible, diesel engines are built for strength, like a bull, whereas gasoline engines are built to gain speed fast, like a cheetah. Depending on the needs of the vehicle, the best engine will be installed.

Passenger cars have the choice between diesel and gasoline engines options because people’s driving styles and driving needs are different. Some prefer the economical and durable diesel engine, while others prefer the speed and the responsiveness of a gasoline engine.

Your diesel engine will require regular maintenance, just like any other piece of machinery. When choosing a company to trust with your engine, make sure that you take into account their previous work and experience.

Propulsion Controls Engineering is a company with over four decades of experience with diesel engines, including many contracts from the US Navy. Contact PCE for any further information you may need.

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Phone: (619) 235-0961
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