6.7 Cummins vs 6.6 Duramax

ShinerBock wrote:

4x4ord wrote:

This bit about natuaral torque coming from a longer stroke is bs. If the displacement remains the same that longer stroke is going to dictate a smaller bore. Torque is a reflection of the amount of heat energy released from the fuel during a power stroke. So it is a function of cylinder volume and volumetric efficiency.



Edit: besides the above the Powerstroke has a longer stroke than the Cummins...... does this mean the Powerstroke pulls like a freight train compared to a Cummins.:)

Torque = force x distance. Longer stroke = longer distance. If two engines are generating the same force to the top of that piston, but one has longer rod turning the crank, then it will have more torque.

Also, the 4.88 inch stroke of the Cummins is much longer than the 4.25 inches of the Powerstroke, and both are longer than the 4.06 inches of the Duramax.

You're right the Cummins has a longer stroke than the Powerstroke ... that was my bad. But stroke length makes no difference to torque if you keep the same displacement. Think of the pressure on the top of the piston in psi. A smaller piston with a longer stroke and or less pistons with a longer stroke means less force on that longer lever. If you think about it you'll come to realize that overall displacement and volumetric efficiency determine the amount of fuel that can be utilized per revolution which determines the torque output of an engine.