2021 Cummins 1075 lbft peak torque at 1356 rpm

Bionic Man wrote:
It’s not all about speed up a hill (especially a hill that very few on this forum ever drive).

RAM needs to change transmission to improve driving dynamics and efficiency. And I’m not sure there is a formula or chart for you to create that will show that.

We know from the Cummins bsfc map peak efficiency is a small window from 1500 - 2000 rpm, and roughly 50% to 75% of peak torque output.

What I'll try is running the model with the engine restricted to 75% torque (say, 800 lb-ft), and forced upshift at 2100 rpm. I bet that's where the 10 spd shines.

To be fair, 43,500 lbs would be a bit much. I'll try 26,000 lbs, 8k truck and 18k toy hauler.

4x4ord wrote:
Comparing the acceleration or even hill climbing traits of a 3.31 10 speed to that of a 4.10 6 speed really needs to be shown in light of comparing the fuel economy in high gear between the two set ups. In order to obtain similar cruising fuel economy the two transmissions would have to be set up with similar final drive ratios .... with final drives equal the advantage of the 10 speed would be revealed comparing acceleration and heavy pulling performance.

Agreed. I was just showing the 6 spd can be tuned for all out performance.

Since the Aisin and 10 speed have similar top gear ratios, by using 4.10 the Aisin would give up a lot on empty cruising mpg.

At the end of the day, there's no denying more gears ARE better, all else being equal.

4x4ord wrote:

Bionic Man wrote:

Cummins12V98 wrote:
" 6 spd vs 10 spd would make very little difference in flat out performance."

I have said this for a LONG time.

You also sang the praises of the 68RFE. Until you moved to the Aisin.....

More gears makes little difference to a 420 hp 1075 lbft engine. My guess is Ram will go to a transmission with more gears and boost the peak Hp to make use of those gears.

It’s not all about speed up a hill (especially a hill that very few on this forum ever drive).

RAM needs to change transmission to improve driving dynamics and efficiency. And I’m not sure there is a formula or chart for you to create that will show that.

RoyJ wrote:
Here's a fun question, what if we "sand-bagged" the PSD with an Aisin 6 speed?

The be fair, I used a 4.10 rear end vs the 3.31 on the 10 speed. Surprise the overall 1st gear ratio becomes nearly identical, so performance is strictly down to gear gap:



The thrust tells us something really interesting:



The Aisin is only able to hit 3rd gear, but the final thrust (and therefore overall gear ratio) is almost an exact match to 4th on the 10 speed. This means given enough time (big enough hill), the Aisin truck will reach the same speed.

Sure enough, my raw data says @ 200 seconds, the Aisin truck hits 44.7 mph, @ 2752 rpm and 475 hp. That's 1 mph faster.

At 190 seconds into the race, the 10 speed has covered 3493 meters, and the Aisin 3494. So the Aisin passed the 10 spd by 3 feet at 3 min 10 sec. It was quite a bit behind at the start.

Comparing the acceleration or even hill climbing traits of a 3.31 10 speed to that of a 4.10 6 speed really needs to be shown in light of comparing the fuel economy in high gear between the two set ups. In order to obtain similar cruising fuel economy the two transmissions would have to be set up with similar final drive ratios .... with final drives equal the advantage of the 10 speed would be revealed comparing acceleration and heavy pulling performance.

RoyJ wrote:
Here's a fun question, what if we "sand-bagged" the PSD with an Aisin 6 speed?

The be fair, I used a 4.10 rear end vs the 3.31 on the 10 speed. Surprise the overall 1st gear ratio becomes nearly identical, so performance is strictly down to gear gap:



The thrust tells us something really interesting:



The Aisin is only able to hit 3rd gear, but the final thrust (and therefore overall gear ratio) is almost an exact match to 4th on the 10 speed. This means given enough time (big enough hill), the Aisin truck will reach the same speed.

Sure enough, my raw data says @ 200 seconds, the Aisin truck hits 44.7 mph, @ 2752 rpm and 475 hp. That's 1 mph faster.

At 190 seconds into the race, the 10 speed has covered 3493 meters, and the Aisin 3494. So the Aisin passed the 10 spd by 3 feet at 3 min 10 sec. It was quite a bit behind at the start.

Comparing the acceleration or even hill climbing traits of a 3.31 10 speed to that of a 4.10 6 speed really needs to be shown in light of comparing the fuel economy in high gear between the two set ups. In order to obtain similar cruising fuel economy the two transmissions would have to be set up with similar final drive ratios .... with final drives equal the advantage of the 10 speed would be revealed comparing acceleration and heavy pulling performance.

Bionic Man wrote:

Cummins12V98 wrote:
" 6 spd vs 10 spd would make very little difference in flat out performance."

I have said this for a LONG time.

You also sang the praises of the 68RFE. Until you moved to the Aisin.....

More gears makes little difference to a 420 hp 1075 lbft engine. My guess is Ram will go to a transmission with more gears and boost the peak Hp to make use of those gears.

Cummins12V98 wrote:
" 6 spd vs 10 spd would make very little difference in flat out performance."

I have said this for a LONG time.

You also sang the praises of the 68RFE. Until you moved to the Aisin.....

Here's distance vs time for both trucks:



Conclusion - if you have a 10 spd racing against your buddy with a 6 speed, time the race to 70 sec, you'll be at 1143m, with him at 1102m. Then say "told ya should've waited, beat your by 120 feet"

If you have the 6 spd, race him to 190 sec, where you pass him and say "told ya a 10 spd is waste of money" ;)

Here's a fun question, what if we "sand-bagged" the PSD with an Aisin 6 speed?

The be fair, I used a 4.10 rear end vs the 3.31 on the 10 speed. Surprise the overall 1st gear ratio becomes nearly identical, so performance is strictly down to gear gap:



The thrust tells us something really interesting:



The Aisin is only able to hit 3rd gear, but the final thrust (and therefore overall gear ratio) is almost an exact match to 4th on the 10 speed. This means given enough time (big enough hill), the Aisin truck will reach the same speed.

Sure enough, my raw data says @ 200 seconds, the Aisin truck hits 44.7 mph, @ 2752 rpm and 475 hp. That's 1 mph faster.

At 190 seconds into the race, the 10 speed has covered 3493 meters, and the Aisin 3494. So the Aisin passed the 10 spd by 3 feet at 3 min 10 sec. It was quite a bit behind at the start.