Why Do Diesels Have More Torque Than Gasoline Engines?

Описание: Most people know Diesels make massive torque, but not everyone knows why. Torque is simply a twisting force created by a lever arm being acted upon by a perpendicular force. A 100lb force applied to a 2 foot long torque wrench, will create 200lb-ft of torque. 200lb applied to a 2 foot torque wrench would be 400lb-ft. In an engine, the throw of the crank (1/2 of the stroke) is the lever arm (think torque wrench) and the force applied to it by the connecting rod is equal to the cylinder pressure multiplied by the surface area of the piston. Increasing the piston, stroke, or cylinder pressure will increase the torque or the engine.

Gasoline cylinder pressure is limited by the auto ignition temperature of the gasoline in the intake charge. Raising the compression ratio or boost pressure will increase the cylinder temperature. If the temperature is high enough, the gasoline will auto ignite before the spark plug ignites. This is called knock or pre-ignition, and it hurts parts.

Diesel is injected at the precise moment that combustion is desired, the knock and pre-ignition are not an issue in a diesel. Therefore, Compression Ratio and Boost can be much higher in a diesel. And that, combined with the longer stroke typical seen in diesels, creates massive torque.