2021 Cummins 1075 lbft peak torque at 1356 rpm

4x4ord wrote:

RoyJ wrote:
Referring back to those BSFC maps I posted, if we want the absolute best mpg, then there's only a small windows (dark blue), between 1500 and 1950 rpm, and 55% to 90% torque output.

That's where a 10 spd would be beautiful.

Roy I think the 3.31 rear end and 5th gear with the Aisin would be hard to beat when towing heavy and when towing light or running empty 6th with 3.31 gears is tough to beat. To bad they did away with 3.31 gears.

4x, this sounds just like a Kaytegism.
IE: It makes no sense. If what you said is true, you’re suggesting the mfg of said vehicle is completely back asswards in their axle offerings. Well, them and every other person who knows generally deeper gears pull better and offer greater fuel efficiency when towing heavy.

4x4ord wrote:

blofgren wrote:
The low RPM massive torque while pulling with the Cummins is one of the things I noticed right away when I bought my truck over having 2 Ford PSD's. I need to hit a considerable hill while towing before having to downshift my truck out of 6th gear, and it is only on really tough pulls that I need to go down another gear from 5th.

The other thing I've noticed is that the Cummins never sounds like it's working hard, even when pulling heavy. I'm quite sold on the inline 6! :B

If you like the way your 2013 Cummins pulls you'd be extremely impressed with the 2020 Powerstroke

I'm sure I would but it will never happen!

I want to show why we don't want 4.10 with a 10 spd, unless you're towing heavy every single day, like a semi tractor.



Cross reference with the BSFC map:



If you're empty, you'd have to drive <70 mph to be in the rpm of peak fuel efficiency. BUT, and that's a big but, at those speeds, even in 10th, you'd never load the engine high enough to be in the peak efficiency zone.

At 70mph we turn 1986 rpm. We need to develop 700 lb-ft with the new engine at that rpm to be at peak fuel efficiency. That's 265 hp. On flat ground, we'll need a 53' semi trailer to need that much hp!

4x4ord wrote:
^^^^ It would be nice to see the bsfc map for the 2021 Cummins. You are right that keeping the torque high and rpm low saves fuel for the heavy trucks that pull hard all day. How or where are you seeing more gears helping the Ram pickup get better fuel economy? Where on that map would you like to see a pickup truck engine run while towing a 16k - 18k trailer down the highway?

Let's build an imaginary pickup heavy hauler. 2021 Cummins dually, 10 spd Ford transmission. We'll have to assume that bsfc map applies to the new engine, with the same torque curve, just shifted up to 1458 N-m.

235/80r17 tires turn 654 rpm @ 60 mph. Let's start with 3.31 gears, here's the rpm in each gear from 45 - 75 mph:



This is where the beauty of the 10 spd shows - at every given speed we can put the engine into the rpm where peak bsfc occurs (~1500 - 2000 rpm). 6th & 7th @ 45mph, 7th or 8th @ 50, 7th & 8th @ 55, 8th & 9th @ 60, 8th & 9th & 10th @ 65, 9th & 10th @ 70, and also 9th & 10th @ 75.

The BEST part is we have 2 to 3 gears to choose and still stay within the optimal RPM. This means we can also pick the gear depending on load to get the engine torque into the optimal range.

Grit dog wrote:
^ Totally agree. And therein lies the best age old argument for a manual trans that ever existed!
I'm smarter than a computer! FWIW, I still believe some of us are when it comes to shifting, as good as the autos have gotten.
One thing to consider is, one can still play big trucker with the little +/- button on the shifter.
Of course we're splitting hairs now. 4speeds, not enough to use a diesel engine most effectively. 5speeds like the torqshift and Alli was a huge improvement. 6 speeds adds the top empty haul @ss across the prairie bobtail gear. 8 to 10 speeds is having your cake and eating it too and 10 is getting a little busy for even a relatively high revving diesel like a pickup truck. I personally think its a couple too many cogs in a gasser truck or car. 8 is the sweet spot for V8 gassers IMO.

If I was strictly using a pickup for towing (not in the city) and hauling, I would still prefer a manual for the exact reason you just mentioned. BUT, based on years of ownership of the last light truck manual trans made (G56 in a Dodge), it is short at least 1 gear maybe 2, to be ideal for heavy work.

Well Grit Dog the biggest issues is that nowadays automatics are stronger than manual transmissions. I will say there are days I miss rowing the gears in our 2001 Ram 2500, but will add towing with the HO/Aisin combination sure is sweet.
The biggest issue with offering a pickup with a manual today is warranty cost! You would have bad drivers tearing up clutches and drive-trains.
To be able to have a clutch able to handle power it would need to be a dual or triple disk clutch.

RoyJ wrote:
Referring back to those BSFC maps I posted, if we want the absolute best mpg, then there's only a small windows (dark blue), between 1500 and 1950 rpm, and 55% to 90% torque output.

That's where a 10 spd would be beautiful.

Roy I think the 3.31 rear end and 5th gear with the Aisin would be hard to beat when towing heavy and when towing light or running empty 6th with 3.31 gears is tough to beat. To bad they did away with 3.31 gears.

^^^^ It would be nice to see the bsfc map for the 2021 Cummins. You are right that keeping the torque high and rpm low saves fuel for the heavy trucks that pull hard all day. How or where are you seeing more gears helping the Ram pickup get better fuel economy? Where on that map would you like to see a pickup truck engine run while towing a 16k - 18k trailer down the highway?

Referring back to those BSFC maps I posted, if we want the absolute best mpg, then there's only a small windows (dark blue), between 1500 and 1950 rpm, and 55% to 90% torque output.

That's where a 10 spd would be beautiful.

Those of you that are looking at the difference in # of gears as a strictly performance issue are missing the boat. Its also about overall driving experience. Running lower RPMs over many miles (not necessarily up the Ike) is simply more relaxing, not to mention the advantage it offers in fuel economy.

I have an 8 speed in my Grand Cherokee EcoDiesel, and the 10 speed in the Expedition MAX. They are both GREAT transmissions. Neither have a problem hunting for gears, and the overall lower RPMs they run just improves the driving experience. I have no doubt that the 10 speeds in the SuperDuty and GM HDs are the same way. RAM is missing the boat here.

^ Totally agree. And therein lies the best age old argument for a manual trans that ever existed!
I'm smarter than a computer! FWIW, I still believe some of us are when it comes to shifting, as good as the autos have gotten.
One thing to consider is, one can still play big trucker with the little +/- button on the shifter.
Of course we're splitting hairs now. 4speeds, not enough to use a diesel engine most effectively. 5speeds like the torqshift and Alli was a huge improvement. 6 speeds adds the top empty haul @ss across the prairie bobtail gear. 8 to 10 speeds is having your cake and eating it too and 10 is getting a little busy for even a relatively high revving diesel like a pickup truck. I personally think its a couple too many cogs in a gasser truck or car. 8 is the sweet spot for V8 gassers IMO.

If I was strictly using a pickup for towing (not in the city) and hauling, I would still prefer a manual for the exact reason you just mentioned. BUT, based on years of ownership of the last light truck manual trans made (G56 in a Dodge), it is short at least 1 gear maybe 2, to be ideal for heavy work.