</font><font color="blue" class="small">( We agree diesel engines by design produce higher torques than gasoline engines, what about steam engines? )</font>
For same cylinder diameter (or piston diameter), same stroke and same amount of fuel per stroke - the torques from engines to engines change only according to fuel type. So, diesel fuel will create higher torque than gasoline due to its higher combustion temperature, hence higher pressure, hence higher force onto piston head, hence higher torque. But the steam isn't flammable and the pressure difference which will create the force onto the piston of a steam engine is created externally - meaning that you can heat the steam outside much much and it can apply much more force/torque than the diesel. But if you heat the steam outside not much, its torque of steam will be less than that of diesel. I mean the torque of steam engine can vary much from very low values to very high values because steam pressure is externally supplied/controlled unlike the diesel and gasoline engines.