FishOnOne wrote:
ShinerBock wrote:
FishOnOne wrote:
SweetLou wrote:
Cummins12V98 wrote:
"When towing, whatever gear keeps engine rpm between 1,800 and 2,000 rpm will give the best fuel mileage and power because that is the rpm window where the Cummins 6.7-liter makes peak torque.
I tow at 60 with rpm's about 1,750. Just right! That's with 4.10's. At 70 I am about 2,000.
With my last DRW I had 3.42's. I would tow in 5th at same rpm's as above, just right!
Exactly right
Exactly wrong.
The 6.7 cummins only makes it's peak torque at wide open throttle and full boost at that rpm and I'm pretty sure no one drives down the highway at wide open throttel.
Fish, I believe you are misunderstanding what is being said here. Generally, engines are more efficient under load around the rpm that they make peak torque. This is actually true for most engines. They are not saying to drive around at WOT.
I guess I'm having a hard time wrapping my head around this. Diesel engines make peak power at WOT and full boost, and typically are most fuel efficient at minimum boost. I'm not sure how that can happen at the same ~ rpms.
It is not about making peak torque. They are just talking about the rpms at which it makes that peak torque.
This is basically what 4x4Ford have been arguing. Towing my 13k 5ver at 65mph would put be at in 6th which is the yellow line below. The red line is about where I am in 5th gear. As you can see, under medium to heavy loads for my gear ratio, I am closer to or actually in the "sweet spot" they were talking about which happens to be around where my engine makes peak torque.
