Ram 2500
Why is the Ram 2500 crewcab longbed with 6.7 Cummins, even though it's only 6 cylinders has more towing power than the similarly equipped Ford F250 powerstroke diesel, the same displacement at 6.7 bu...
Forum Discussion
Flashman wrote:
Can't argue that - but notice how all the Semis are straight 6s - and torque is of prime consideration for them.
Semi's mainly use inline six engines due to how simple they are to work on, how simple they are to design(resize), their natural balance, and the design of a straight six favors torque due to the longer stroke that can be achieved versus a V8 design in the given space of a semi's engine bay.
It's mainly about the bore/stroke ratio as to when an engine gets it's peak torque. An oversquare engine is considered a short stroke, and has a larger bore that its piston stroke. These types of engines favor high revs to make their torque due to their short throw which more rpms creates higher horsepower numbers. An undersquare engine is considered a long stroke, and has a stroke that is longer than its bore. These types of engines make their peak torque really early with a very long throw, but do not favor high revs which means they usually do not create that much horsepower compared to a short stroke. Due to their tall and narrow design, inline six's are able to have a longer stroke that a V8 in the long and narrow engine bay of a Semi truck. The V8 would have a shorter stroke in order to fit which would mean higher rpm torque. Higher rpm torque is not ideal for towing.
On a side note the Cummins and Powerstroke 6.7L are both long stroke(undersquare) engines, but the Duramax 6.6L is a short stroke(oversquare).
