2021 Cummins 1075 lbft peak torque at 1356 rpm

lenr wrote:
So, this is the second thread that I have followed recently where the higher torque rise of the Cummins engine is discussed as a good thing. I have tried to think through why that is good, and all I can come up with is that it reduces the need to shift to a lower gear as load increases. In the days of manual transmissions shifting was something to be considered. With automatic transmissions, no big deal. As said above a downshift in a 3 or 4 speed transmission was a big jump in RMP, and again something to be minimized. Modern automatics are highly reliable and can shift without a reduction of longevity. The 8 to 10 speed transmissions exist to achieve the best ratio for given load and speed, so they need to shift to accomplish that. In my Ford with its less torque rise and a 6R140 transmission, gear hunting is not a problem, but if gear hunting starts, locking out a gear or switching to Tow-Haul mode solves it. Also, in a torque wars world where all the engines are similar at low end torque, I am fine with the engine having less torque rise since that means more HP at the top end. Top end HP is what accelerates my rig up to speed the fastest and pulls the mountain the fastest in whatever gear the transmissions determines. The Ford 6.7 consistently excels in HP while keeping up with the competition in torque.

To see the benefit of torque rise, you'd have to look at the BSFC (brake specific fuel efficiency) curve / maps.

Hi torque rise is another way of saying near-constant hp within an rpm range. If you can "lug" an engine down to 2200 rpm and make the same hp as 2800 rpm, you often do so with better fuel efficiency. Here's a map (Shiner's) of the older engine:



This is why all big trucks (like that 2020 Volvo) are shifting towards low rpm / high torque, over revving it out like an old Detroit.