2021 Cummins 1075 lbft peak torque at 1356 rpm
Apparently the 2021 Cummins makes its peak torque of 1075 lbft at 1356 rpm. Are you still impressed?
Forum Discussion
I'll try explaining what I'm trying to get at again: I think the Ford uses the lower rpm range of its power band from about 2200 to 2700 rpm. This doesn't make best use of its higher power or provide for smooth shift points.
Say a Ford dually with a heavy load starts climbing a hill at 70 mph in 7th gear at 2700 rpm. As the hill slows the truck from 70 mph to 57 mph, the slowing engine develops about 13% more torque (from 920 @ 2700 rpm to 1018 @ 2200 rpm). At this point the transmission drops to 6th gear. When the transmission shifts to 6th, the engine revs from 2200 rpm and 1018 lbft to 2800 rpm and 880 lbft. In 7th gear the output shaft of the transmission was turning 2200 rpm and was delivering 1018 lbft of torque.... after the shift the output shaft of the transmission is still turning 2200 rpm but is now delivering 1124 lb ft of torque (880 lbft x 1.277 6th gear ratio). So as the truck slows in 7th gear, the transmission output shaft torque slowly rises 13%, then it shifts to 6th and boom there is an instant 10% jump in torque. The Ford would be even worse if it only had 6 gears.
With the Cummins and even though it only has 6 gear ratios this doesn't happen. The engine slows from 2700 to 2200 and the torque rises from 818 lbft to 968 lbft ... about 18%, then it shifts to third and the engine rpm revs to about 2926 rpm. So the torque on the transmission output shaft goes from 2200 rpm and 968 lbft before the shift to 2200 rpm and 987 lbft (742 lbft x 1.33 gear ratio) after the shift... about a 2% increase in torque.
If the Ford was tuned to shift at higher rpms it would behave a little more like the Cummins. Maybe it's not a big deal but I thought it was worth noting.
Edit: bottom line is, I’ve heard some of you Cummins guys talk about wanting more gears but you don’t need them. I think if I was going to be pulling heavy trailers on long steep grades I’d rather have the Cummins with a 6 speed than a more powerful, gear hunting, Powerstroke and 10 speeds.
Say a Ford dually with a heavy load starts climbing a hill at 70 mph in 7th gear at 2700 rpm. As the hill slows the truck from 70 mph to 57 mph, the slowing engine develops about 13% more torque (from 920 @ 2700 rpm to 1018 @ 2200 rpm). At this point the transmission drops to 6th gear. When the transmission shifts to 6th, the engine revs from 2200 rpm and 1018 lbft to 2800 rpm and 880 lbft. In 7th gear the output shaft of the transmission was turning 2200 rpm and was delivering 1018 lbft of torque.... after the shift the output shaft of the transmission is still turning 2200 rpm but is now delivering 1124 lb ft of torque (880 lbft x 1.277 6th gear ratio). So as the truck slows in 7th gear, the transmission output shaft torque slowly rises 13%, then it shifts to 6th and boom there is an instant 10% jump in torque. The Ford would be even worse if it only had 6 gears.
With the Cummins and even though it only has 6 gear ratios this doesn't happen. The engine slows from 2700 to 2200 and the torque rises from 818 lbft to 968 lbft ... about 18%, then it shifts to third and the engine rpm revs to about 2926 rpm. So the torque on the transmission output shaft goes from 2200 rpm and 968 lbft before the shift to 2200 rpm and 987 lbft (742 lbft x 1.33 gear ratio) after the shift... about a 2% increase in torque.
If the Ford was tuned to shift at higher rpms it would behave a little more like the Cummins. Maybe it's not a big deal but I thought it was worth noting.
Edit: bottom line is, I’ve heard some of you Cummins guys talk about wanting more gears but you don’t need them. I think if I was going to be pulling heavy trailers on long steep grades I’d rather have the Cummins with a 6 speed than a more powerful, gear hunting, Powerstroke and 10 speeds.
