4x4ord wrote:
Yes. The current model Cummins makes 343 HP at 1800 rpm ..... At what HP or torque level would you say this engine is lightly loaded while turning 1800 rpm? What about the Powerstroke ... it makes about 360 HP at 1800 rpm. I might say under 50% load but could we agree that usually under 40% load at a given rpm would constitute a light load? That percentage would be significantly lower for many aftermarket tuned engines. Bottom line is we can only guess what gear our truck should be in at any given load and rpm. The engineers who design these trucks could very easily program them to pick the right gear for fuel economy .... If they don't take fuel economy into account when they program the shifting strategy I certainly don't know why they don't but it's not because it is too complicated for them.
"Light load" is indeed too arbitrary, I prefer to look at the lands on the BSFC map, and set a lower boundary as "light load". Here's a map Shiner posted on the other post:
If we use 200-210 as the lower fuel efficiency limit, then on the old engine 480 lb-ft is our light loaded limit, and the 2019 can reach down to 400 lb-ft at certain rpm, and still achieve a favourable efficiency.
At 300 lb-ft, the engine loading is too light, and we need an upshift to load it into a favourable map land.
Wish we can find a map for the post-2019 Powerstroke. But I wouldn't be surprised if OEM transmission logic takes these maps heavily into account. For "tow haul" map, they may assume you're heavily loading the engine, and thus mileage will suffer if you purposely use that mode under a light load.
