Good Sam Club Open Roads Forum: 2021 Cummins 1075 lbft peak torque at 1356 rpm
Open Roads Forum Already a member? Login here.   If not, Register Today!  |  Help

Newest  |  Active  |  Popular  |  RVing FAQ Forum Rules  |  Forum Posting Help and Support  |  Contact  

Search:   Advanced Search

Search only in Tow Vehicles

Open Roads Forum  >  Tow Vehicles

 > 2021 Cummins 1075 lbft peak torque at 1356 rpm

Reply to Topic  |  Subscribe  |  Print Page  |  Post New Topic  | 
Page of 15  
Prev  |  Next
Cummins12V98

on the road

Senior Member

Joined: 06/03/2012

View Profile


Offline
Posted: 01/04/21 07:44pm Link  |  Quote  |  Print  |  Notify Moderator

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.


[emoticon] I didn't think I was confused but now I'm beginning to think I must be.[emoticon]


Clear as the Palm Springs, CA skies today!


2015 RAM LongHorn 3500 Dually CrewCab 4X4 CUMMINS/AISIN RearAir 385HP/865TQ 4:10's
37,800# GCVWR "Towing Beast"

"HeavyWeight" B&W RVK3600

2016 MobileSuites 39TKSB3 highly "Elited" In the stable

2007.5 Mobile Suites 36 SB3 29,000# Combined SOLD

Me Again

Sunbird(Wa)/snowbird(Az)

Senior Member

Joined: 09/26/2012

View Profile



Good Sam RV Club Member

Offline
Posted: 01/04/21 08:03pm Link  |  Quote  |  Print  |  Notify Moderator

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.


[emoticon] I didn't think I was confused but now I'm beginning to think I must be.[emoticon]


Clear as the Palm Springs, CA skies today!


Cloudy day there today Ron?


2015 RAM 3500 CC SB SRW Our Rig New 2017 Bighorn 3575el. Commuter trailer 2019 Laredo 225MK. Retired and enjoying it!


4x4ord

Alberta

Senior Member

Joined: 12/23/2010

View Profile



Posted: 01/04/21 09:02pm Link  |  Quote  |  Print  |  Notify Moderator

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.

* This post was last edited 01/05/21 04:23am by 4x4ord *   View edit history


2017 F350 SRW Platinum short box 4x4.
B&W Companion
2008 Citation Platinum XL 34.5

Grit dog

Black Diamond, WA

Senior Member

Joined: 05/06/2013

View Profile


Offline
Posted: 01/04/21 11:17pm Link  |  Quote  |  Print  |  Notify Moderator

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.


"Yes Sir, Oct 10 1888, Those poor school children froze to death in their tracks. They did not even find them until Spring. Especially hard hit were the ones who had to trek uphill to school both ways, with no shoes." -Bert A.

Me Again

Sunbird(Wa)/snowbird(Az)

Senior Member

Joined: 09/26/2012

View Profile



Good Sam RV Club Member

Offline
Posted: 01/05/21 06:51am Link  |  Quote  |  Print  |  Notify Moderator

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

4x4ord

Alberta

Senior Member

Joined: 12/23/2010

View Profile



Posted: 01/05/21 09:11am Link  |  Quote  |  Print  |  Notify Moderator

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.

4x4ord

Alberta

Senior Member

Joined: 12/23/2010

View Profile



Posted: 01/05/21 09:52am Link  |  Quote  |  Print  |  Notify Moderator

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.

specta

utah

Senior Member

Joined: 06/18/2001

View Profile



Posted: 01/05/21 10:02am Link  |  Quote  |  Print  |  Notify Moderator

[image]

[image]

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. [emoticon]

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


Kenny
2011 Chevy 2500 HD 6.0L 4wd
Regular cab. The best looking trucks.
1995 Lance 945 Onan QG 2500 LP
6580 lb truck 10540 fully loaded


4x4ord

Alberta

Senior Member

Joined: 12/23/2010

View Profile



Posted: 01/05/21 10:20am Link  |  Quote  |  Print  |  Notify Moderator

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

[image]

specta

utah

Senior Member

Joined: 06/18/2001

View Profile



Posted: 01/05/21 11:23am Link  |  Quote  |  Print  |  Notify Moderator

4x4ord wrote:

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

[image]


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.

Reply to Topic  |  Subscribe  |  Print Page  |  Post New Topic  | 
Page of 15  
Prev  |  Next

Open Roads Forum  >  Tow Vehicles

 > 2021 Cummins 1075 lbft peak torque at 1356 rpm
Search:   Advanced Search

Search only in Tow Vehicles


New posts No new posts
Closed, new posts Closed, no new posts
Moved, new posts Moved, no new posts

Adjust text size:




© 2021 CWI, Inc. © 2021 Good Sam Enterprises, LLC. All Rights Reserved.