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Open Roads Forum  >  Tow Vehicles

 > 2021 Cummins 1075 lbft peak torque at 1356 rpm

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4x4ord

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Posted: 12/29/20 05:15pm Link  |  Quote  |  Print  |  Notify Moderator

Apparently the 2021 Cummins makes its peak torque of 1075 lbft at 1356 rpm. Are you still impressed?


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Lwiddis

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Posted: 12/29/20 05:33pm Link  |  Quote  |  Print  |  Notify Moderator

Most definitely!


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Posted: 12/29/20 05:34pm Link  |  Quote  |  Print  |  Notify Moderator

Well heck yeah, are you? I think Cummins can play hopscotch with Ford on this platform till around 1250 ft-lbs or maybe even 1300 ft-lbs of torque. They probably can go higher w a different tranny.

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Posted: 12/29/20 05:44pm Link  |  Quote  |  Print  |  Notify Moderator

4x4ord wrote:

Apparently the 2021 Cummins makes its peak torque of 1075 lbft at 1356 rpm. Are you still impressed?


Yep, that CP3 pump going in the 2021's is the bomb!


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Cummins12V98

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Posted: 12/29/20 06:07pm Link  |  Quote  |  Print  |  Notify Moderator

4x4ord what's your next truck now???


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Posted: 12/29/20 06:42pm Link  |  Quote  |  Print  |  Notify Moderator

4x4ord wrote:

Apparently the 2021 Cummins makes its peak torque of 1075 lbft at 1356 rpm. Are you still impressed?


Ram also increased their HP to 430


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4x4ord

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Posted: 12/30/20 12:01am Link  |  Quote  |  Print  |  Notify Moderator

MikeRP wrote:

Well heck yeah, are you? I think Cummins can play hopscotch with Ford on this platform till around 1250 ft-lbs or maybe even 1300 ft-lbs of torque. They probably can go higher w a different tranny.


I'm disappointed to hear that the 1075 torque rating is at such a low rpm. Here's why: When the 400 HP @ 2800 rpm and 1000 lbft @ 1800 rpm Cummins came out it had a power curve designed to pull and the numbers were meaningful. If you think of the 2019 Ram coming to a hill and you put your foot into it the transmission drops a couple of gears the engine rpm jumps to 2800 rpm and you've got 400 horsepower and 750 lbft of torque at the flywheel. As the hill starts to get steeper the engine pulls down and for every 100 rpm that is lost the crankshaft torque rises about 25 lbft so that by the time the engine slows to 2100 rpm it is still making 370 HP (and about 925 lbft of torque). At 2100 engine rpm the transmission can downshift to third and the power jumps back up to 400 horses. So, the Cummins engine doesn't really have much need for any more than a 6 speed transmission to make very good use of its power. For 2021, the 1075 lbft at 1356 rpm is strictly a rating to gain bragging rights and has absolutely nothing to do with how the engine will perform. In my opinion it is a number that Ram talked Cummins into giving them to gain bragging rights. It ends up being meaningless because it is so far outside of the operating rpm of the engine. It tells us that at 1356 rpm the engine is only capable of 277 HP. More than likely the torque curve of the 2021 is almost identical to that of the outgoing engine at the lower rpm of the engine's operating range. The big news really is that the CP3 pump is back for 2021. The fact that the power rating is up to 430 HP for 2021 is of some significance I guess.

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Posted: 12/30/20 02:23am Link  |  Quote  |  Print  |  Notify Moderator

4x4ord wrote:

MikeRP wrote:

Well heck yeah, are you? I think Cummins can play hopscotch with Ford on this platform till around 1250 ft-lbs or maybe even 1300 ft-lbs of torque. They probably can go higher w a different tranny.


I'm disappointed to hear that the 1075 torque rating is at such a low rpm. Here's why: When the 400 HP @ 2800 rpm and 1000 lbft @ 1800 rpm Cummins came out it had a power curve designed to pull and the numbers were meaningful. If you think of the 2019 Ram coming to a hill and you put your foot into it the transmission drops a couple of gears the engine rpm jumps to 2800 rpm and you've got 400 horsepower and 750 lbft of torque at the flywheel. As the hill starts to get steeper the engine pulls down and for every 100 rpm that is lost the crankshaft torque rises about 25 lbft so that by the time the engine slows to 2100 rpm it is still making 370 HP (and about 925 lbft of torque). At 2100 engine rpm the transmission can downshift to third and the power jumps back up to 400 horses. So, the Cummins engine doesn't really have much need for any more than a 6 speed transmission to make very good use of its power. For 2021, the 1075 lbft at 1356 rpm is strictly a rating to gain bragging rights and has absolutely nothing to do with how the engine will perform. In my opinion it is a number that Ram talked Cummins into giving them to gain bragging rights. It ends up being meaningless because it is so far outside of the operating rpm of the engine. It tells us that at 1356 rpm the engine is only capable of 277 HP. More than likely the torque curve of the 2021 is almost identical to that of the outgoing engine at the lower rpm of the engine's operating range. The big news really is that the CP3 pump is back for 2021. The fact that the power rating is up to 430 HP for 2021 is of some significance I guess.


Your point is valid IF hp was unchanged. With 430 hp, the torque at every given rpm will be higher compared to the 2020 model.

The ability to lug down to 1356 rpm is probably for fuel economy, where a given hill can be climbed at 277 hp and maintain peak bsfc. Modern semis use similar strategy, with some developing peak torque at sub-1000 rpm.

I wonder why they specified a CP4 in the first place. First thought was emissions / injection pressure, but obviously they found a workaround

4x4ord

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Posted: 12/30/20 07:02am Link  |  Quote  |  Print  |  Notify Moderator

^^^^ You may be right that developing peak torque down at 1356 rpm may indicate the new power curve has potential for better fuel economy. It will be interesting to see if that’s the case. But, imagine pulling a heavy high profile trailer into a stiff wind or up a slight grade were 277 hp is required, Your right foot would be through the floor board and you’re in 6th gear at 1356 rpm. I can’t imagine a 430 hp engine being programmed to ever run down at such a low rpm at full throttle when it is only capable of 277 hp at that rpm. You are probably right though, the 2021 will likely hold onto the top gears a little longer to make use of the torque at lower rpms for fuel efficiency. The big diesels in the semis do create maximum torque at very low rpm but they are still producing close to maximum power at that rpm as well. The Cummins x15 for instance can be ordered with 400 to 500 hp at an engine rpm of 1700. It has a peak torque of 1850 rpm. If that peak torque is produced at 1000 rpm the engine is still putting out up to 88% of rated power. Even with the 500 hp engine a torque rating at 1000 rpm is at about 60% of rated engine speed.... so it is a meaningful number.

valhalla360

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Posted: 12/30/20 07:38am Link  |  Quote  |  Print  |  Notify Moderator

Technologically...sort of...I mean semi engines have been able to beat that for many years.

In practical terms, once you can drag a 20k lb trailer up a steep grade without losing any speed or the engine struggling...it becomes mostly about who bought the bigger codpiece.


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