Why Diesel Engines Produce Higher Torque than Gas Engines
Torque is the measure of force that causes an object to rotate about an axis. On car engines, it is the force that spins the engine crankshaft, and to the driver, it feels like the “guts” of the motor, or the “pulling” force when trying to climb steep hills. Although gasoline internal combustion engines are generally more powerful compared to diesels, the latter play at a wholly different league when it comes to generating torque.
So why is it that diesel engines, although less powerful than their gasoline counterparts, have noticeably higher torque?
Diesel engines don’t use sparks to ignite the air-fuel mixture inside the combustion chamber. Instead, they rely on high compression ratios that will cause it to ignite due to the high pressure that builds up in the closed chamber (thermodynamics). This makes diesel engines work in a more cumbersome fashion, so they can’t reach high revs as easily as gas engines do. However, the force pushing the piston rod down resulting in the spinning of the crankshaft is significantly larger, precisely thanks to this method of ignition.
Another element that adds to this effect is the energy density of diesel fuel, which is higher than that of gasoline. We must also not forget that turbochargers are often paired with diesel engines, compressing more air inside the combustion chamber, magnifying the “energy density” effect. This means that with every combustion event, there’s more energy that is released and transformed in kinetic force.
This force has the form of regressive movement on the piston, which is then transformed into spinning action on the crankshaft. Because the stroke length in diesel motors is generally longer than that of gas engines, more torque is generated for the same amount of force. Remember, torque equals force multiplied by distance, so the longer the stroke, the higher the torque value.