2021 Cummins 1075 lbft peak torque at 1356 rpm

4x4ord wrote:
^^^^I guess you've probably seen this:

Nope, never have but thank you.

Probably because I really have no interest in big trucks. LOL
Or diesels in general.

But those numbers of the new diesel pickups are impressive.

The truck is governed to 68 mph, about 1300 rpm. I was averaging about 11.5 mpg.

^^^^I guess you've probably seen this:

Impressive numbers for sure.
Here's my work truck, a 2020 Volvo.
10.8L 659 cid, 1250 lb ft and 325 hp at 1700 rpm. 12-speed manual "air-shift" trans.

The scheduled oil changes for this truck is every 50,000 miles. :E

First oil change was done at 20,000 miles. Next scheduled service is at 70,000 miles.

Grit dog wrote:
Or, assuming your calculated rpm at certain speeds and certain gears, regardless of vehicle, the closer the gear splits (more available gear ratios within a certain speed range), the less of a rpm jump or drop and the greater the ability to match desired speed, and rpms (up/tq) balance.
I’d argue if your numbers are right, dropping or gaining 500-600 rpms with a single gear shift is not ideal and more available ratios will only serve to improve performance by staying ever closer to the perfect sweet spot at more given road speeds.
Does the 10 speed Ford really have 500 rpm drops between gears especially in the upper gears? If so, I’d say it doesn’t have ideal ratios for towing and maybe wasted a gear or 2 too many on upper high speed “cruising” gears.
The 6 speed is good but not ideal, talking Cummins or any other diesel pickup. The more the merrier.

There’s a reason heavy haulers have 18 speeds, besides the big engines havin a much smaller useable rpm range, it’s also to keep the truck putting out the most available power to the ground over the greatest speed range.
Or simply put, more gears the better, within reason.

I very seldom use the 18 speeds in our big trucks but it is nice to have them. Empty I will jump across 4 gears at times. Loaded I usually use every second gear until I'm cruising. If the engine is happy at 1200 rpm I keep it in that gear, if there is a bit of a wind and I need to pick the rpm up a little I'll drop 1/2 gear. If I hit a hill and I know I'm going to be dropping multiply gears I'll drop 2 gears to bring the engine rpm up to 2000 or 2100. So the gears are nice to have.

When you compare the power curves of the Cummins to the Powerstroke you can see that running at 2100 rpm with the Cummins is no big deal .... you're only giving up at the most 20 horses and if the engine slows the power is only dropping off slightly. So, it's time to downshift if the hill is slowing the truck more but it's a good place to be if the engine and hill are at an equilibrium or if the engine is gaining a bit on the hill.
The Powerstroke, on the other hand, even with a 10 speed is giving up about 65 HP by running at 2100rpm with your foot to the floor in 7th vs 2682 in 6th. So it downshifts and when the load is steady the jump in HP will cause the truck to accelerate ... so it does. And now your revving at 2800 rpm and on the verge of an upshift as soon as the hill relaxes even just a bit... and the cycle continues.

So the Powerstroke needs 10 gears to use its power band and it will beat the Cummins up the hill, but, even with its 10 gears it doesn't have the beautiful pulling characteristics of an engine with a 36% torque rise. If Ford could push the torque up to 1200 lbft @ 2000 rpm and leave the power where it is then we would have the cat by the tail.

Grit dog wrote:
Or, assuming your calculated rpm at certain speeds and certain gears, regardless of vehicle, the closer the gear splits (more available gear ratios within a certain speed range), the less of a rpm jump or drop and the greater the ability to match desired speed, and rpms (up/tq) balance.
I’d argue if your numbers are right, dropping or gaining 500-600 rpms with a single gear shift is not ideal and more available ratios will only serve to improve performance by staying ever closer to the perfect sweet spot at more given road speeds.
Does the 10 speed Ford really have 500 rpm drops between gears especially in the upper gears? If so, I’d say it doesn’t have ideal ratios for towing and maybe wasted a gear or 2 too many on upper high speed “cruising” gears.
The 6 speed is good but not ideal, talking Cummins or any other diesel pickup. The more the merrier.
There’s a reason heavy haulers have 18 speeds, besides the big engines havin a much smaller useable rpm range, it’s also to keep the truck putting out the most available power to the ground over the greatest speed range.
Or simply put, more gears the better, within reason.

7 th gear is 1:1 in the 10r140 and 6th is 1.277:1. So a downshift at 2114 rpm in 7th brings the engine speed to 2700 in 6th. 5th is 1.519 :1 so dropping from 6th at 2270 rpm would bring the engine up 2700 in 5th.

I already have the Cummins 6 speed T-shirt, hat and merit badge!

Or, assuming your calculated rpm at certain speeds and certain gears, regardless of vehicle, the closer the gear splits (more available gear ratios within a certain speed range), the less of a rpm jump or drop and the greater the ability to match desired speed, and rpms (up/tq) balance.
I’d argue if your numbers are right, dropping or gaining 500-600 rpms with a single gear shift is not ideal and more available ratios will only serve to improve performance by staying ever closer to the perfect sweet spot at more given road speeds.
Does the 10 speed Ford really have 500 rpm drops between gears especially in the upper gears? If so, I’d say it doesn’t have ideal ratios for towing and maybe wasted a gear or 2 too many on upper high speed “cruising” gears.
The 6 speed is good but not ideal, talking Cummins or any other diesel pickup. The more the merrier.
There’s a reason heavy haulers have 18 speeds, besides the big engines havin a much smaller useable rpm range, it’s also to keep the truck putting out the most available power to the ground over the greatest speed range.
Or simply put, more gears the better, within reason.

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.

Cummins12V98 wrote:

4x4ord wrote:

spoon059 wrote:

Grit dog wrote:
^ I understand the concept and terminology. I'm simply confused as to what your point is.

So is he.

:h I didn't think I was confused but now I'm beginning to think I must be.:)

Clear as the Palm Springs, CA skies today!

Cloudy day there today Ron?

4x4ord wrote:

spoon059 wrote:

Grit dog wrote:
^ I understand the concept and terminology. I'm simply confused as to what your point is.

So is he.

:h I didn't think I was confused but now I'm beginning to think I must be.:)

Clear as the Palm Springs, CA skies today!