Hi,

The short answer is yes. There are lots of factors in the design details of a diesel engine, but in general diesels have their maximum torque at a lower rpm than a similar gas engine. This is related to the fact that the combustion process in a diesel is slower and tends to provide a more constant pressure on the piston during the "power" stroke. If you operate a diesel at higher speeds, the pistions move faster and tend to "get ahead" of the expansion of the gases due to combustion. This results in a reduction of torque at higher rpms.

In a gas engine, with much faster combustion, the torque tends to increase at higher rpms where the speed of the pistion and the speed of the expanding gas is "better matched".

Having said all that, modern diesel engines do not really operate with constant pressure during the entire combustion process. In the interest of efficiency, modern diesels have the combustion process begin prior to the start of the "power stroke" resulting in an increase of pressure prior to the start of the stroke, followed by a (more or less) constant pressure expansion process. But you are correct, this design results in more usable torque at lower rpms.