F450 vs Ram 3500 DRW tow vehicle

4x4ord wrote:


Edit: It should be noted that the Cummins is tuned for a little higher rpm than the Powerstroke. (Powerstroke makes peak HP at 2600 rpm vs 2800 for the Cummins and peak torque at 1600 vs 17 or 1800 rpm for the Cummins). Likely the Powerstroke BSFC map would favor lower rpm.

The Cummins in the map above is not the HO Cummins. It is the standard output that reaches peak torque at 1,700 rpm. Horsepower on the top end is irrelevant here. I would wager that bore/stroke ratio would have a significant impact on where this island is for each engine.

The Cummins is a longer stroke engine(.86:1) with more of what I refer to as natural torque on the low end. Meaning that it makes a lot of low end torque without utilizing as much boost or additional fueling to alter its peak. The Powerstroke is still a long stroke engine(.91:1), but utilizes VGT to alter peak torque placement. The Duramax L5P is actually a short stroke(1.04:1) and achieves peak torque at 1,600 rpm as well. Because of this, I would be willing to bet that the Cummins would have it's island at a lower rpm range than the rest. Just my hunch.