6.7 Cummins vs 6.6 Duramax

ShinerBock wrote:

RCMAN46 wrote:
"They also operate at lower engine rpms, which lowers the piston speed. Pretty much an irrelevant negative on the I-6!"

If you are comparing the Cummins with the Duramax then you are dead wrong.


Here are the facts.

The Cummins makes its peak torque at 1800 rpm
The Duramax makes its peak torque at 1600 rpm

The Cummins makes its max horsepower at 2800 rpm.
The Duramax makes its max horsepower at 2800 rpm.

So much for the popular belief that the I6 Cummins operates at a lower rpm than the v8 Duramax.

So the statement that the Cummins operates at a higher piston speed holds true when comparing to the Duramax.

While I have been trying to stay away from this pissing match thread, there is more to this than peak torque/horsepower at wide open throttle where hardly any one drives at. The RPM peak torque is achieved at wide open throttle is mainly dictated by electronically controlled VG turbos anyways. However, under normal driving conditions there is what I refer to as natural torque and boost assisted torque and makes a bug difference in how the truck drives when not at wide open throttle.

Due to the longer stroke of the Cummins, it makes more natural low end torque without the assistance of the turbo. This is why people always say a Cummins pulls like a train because it generates so much torque at low revs under normal driving conditions. This is also why Pickuptrucks.com and a few of the other review sites have said that the Cummins feels least phased by loads compared to the other two under normal driving conditions especially under 1,600 rpm.

The short stroke Duramax on the other hand utilizes the turbo more to achieve its torque at low rpm under normal driving conditions. Giver here the throttle and it will blow the doors off of the Ram, but it feels likes it has less torque under 1,600 rpm versus the Cummins in normal driving conditions until the turbos are spooled. When I was driving my cousins L5P, you did not get the same torque pull feel until higher rpms as you did on my truck at just 1,400 rpm.

Not trying to dis the Duramax because it is a great engine and is very quick at wide open throttle in stock form versus the other two if that is what you are after, but it does feel like it has less torque at low rpms in normal driving conditions versus the Cummins regardless of when it's turbo is programmed to achieve peak torque at wide open throttle. Drive and tow with both back to back and you will see what mean. My brother even says the same about his old 2012 PSD versus his current 2014 CTD and my father in law with his 2018 PSD versus my CTD.

This bit about natuaral torque coming from a longer stroke is bs. If the displacement remains the same that longer stroke is going to dictate a smaller bore. Torque is a reflection of the amount of heat energy released from the fuel during a power stroke. So it is a function of cylinder volume and volumetric efficiency.



Edit: besides the above the Powerstroke has a longer stroke than the Cummins...... does this mean the Powerstroke pulls like a freight train compared to a Cummins.:)

Me Again wrote:

memtb wrote:


If it floats, flies, or rolls....it was meant to be raced!

And you speed shift your RAM manual tranny, NOT!

I never said that I “race” my truck.....only defended those that want to to do so! It’s really “not” that complicated! For most people!:S

RCMAN46 wrote:
"They also operate at lower engine rpms, which lowers the piston speed. Pretty much an irrelevant negative on the I-6!"

If you are comparing the Cummins with the Duramax then you are dead wrong.


Here are the facts.

The Cummins makes its peak torque at 1800 rpm
The Duramax makes its peak torque at 1600 rpm

The Cummins makes its max horsepower at 2800 rpm.
The Duramax makes its max horsepower at 2800 rpm.

So much for the popular belief that the I6 Cummins operates at a lower rpm than the v8 Duramax.

So the statement that the Cummins operates at a higher piston speed holds true when comparing to the Duramax.

While I have been trying to stay away from this thread, there is more to this than peak torque/horsepower at wide open throttle where hardly any one drives at. The RPM peak torque is achieved at wide open throttle is mainly dictated by electronically controlled VG turbos anyways. However, under normal driving conditions there is what I refer to as natural torque and boost assisted torque and makes a bug difference in how the truck drives when not at wide open throttle.

Due to the longer stroke of the Cummins, it makes more natural low end torque without the assistance of the turbo. This is why people always say a Cummins pulls like a train because it generates so much torque at low revs under normal driving conditions. This is also why Pickuptrucks.com and a few of the other review sites have said that the Cummins feels least phased by loads compared to the other two under normal driving conditions especially under 1,600 rpm.

The short stroke Duramax on the other hand utilizes the turbo more to achieve its torque at low rpm under normal driving conditions. Giver here the throttle and it will blow the doors off of the Ram, but it feels likes it has less torque under 1,600 rpm versus the Cummins in normal driving conditions until the turbos are spooled. When I was driving my cousins L5P, you did not get the same torque pull feel until higher rpms as you did on my truck at just 1,400 rpm.

Not trying to dis the Duramax because it is a great engine and is very quick at wide open throttle in stock form versus the other two if that is what you are after, but it does feel like it has less torque at low rpms in normal driving conditions versus the Cummins regardless of when it's turbo is programmed to achieve peak torque at wide open throttle. Drive and tow with both back to back and you will see what mean. My brother even says the same about his old 2012 PSD versus his current 2014 CTD and my father in law with his 2018 PSD versus my CTD.

memtb wrote:


If it floats, flies, or rolls....it was meant to be raced!

And you speed shift your RAM manual tranny, NOT!

SweetLou wrote:
Has any one considered recalls on ea brand or the maintenance costs for EGR or other servicing? It would play into my decisions, but at the end of the day, a lot goes into buying a new truck not just what they can out pull or if they get off the line quicker. That one still amazes me why they think racing an almost 8000 lb truck is even relevant.

If it floats, flies, or rolls....it was meant to be raced!

SweetLou wrote:
Has any one considered recalls on ea brand or the maintenance costs for EGR or other servicing? It would play into my decisions, but at the end of the day, a lot goes into buying a new truck not just what they can out pull or if they get off the line quicker. That one still amazes me why they think racing an almost 8000 lb truck is even relevant.

They are not really racing 8,000lb trucks. You hook 32,000lbs on the back and then race 40,000lb rigs!

Has any one considered recalls on ea brand or the maintenance costs for EGR or other servicing? It would play into my decisions, but at the end of the day, a lot goes into buying a new truck not just what they can out pull or if they get off the line quicker. That one still amazes me why they think racing an almost 8000 lb truck is even relevant.

I have owned both. Both served me well. Power wise if buying new it doesn't matter anymore. You could hook either to a 30ft trailer and floor the go peddle and turn it into a 34 footer. If I was buying new I'd go with the ram cummins. They have improved the pickup itself a lot in the last few years. My chevy duramax 2002 was much quieter, the ride was better, it drove better and over all had a much nicer cab then what I have now, a 2006 Ram cummins. With that said I like the cummins enough better that I would buy it again. However if anyone is giving away any one of the big 3 with the diesel engine I'll be happy to take it. I'm pretty sure any new one will probably outlast me :)

Cummins12V98 wrote:
Here is another thing to consider. What does CUMMINS do??? They build engines!

They sell the 6.7 to RAM but they also sell the same engine to others for Medium Duty applications. "True medium duty"

GM's D Max is used by what other Medium Duty Manufacturers? "Crickets"

Same goes for the Medium Duty AISIN transmission as it's used in many other MD applications.

"ALLISON" (GM Built), who else uses that trans for MD applications? "Crickets"

Well let's add another thing to chew on. Simply look around out on the Highways. What brand DOMINATES the "Independently Owned" RV and HotShot hauling market. RAM, there is simply no comparison.

Oh, they use them a lot to haul Fords. ;)

how many people buy a 3/4 or 1 ton truck for PERSONAL use and put 200K + miles of towing heavy loads on it let alone, 500K or so? Yes there are some, but most won't see enough miles or load to make a reliability difference on what the engine and transmission was designed for.

All three engines, transmissions and bodies are plenty fine and reliable.

I know owners of Dodge,Ford and GM that have put 250K + miles and had no reliability issues, just normal service by the book.

Drive them all and pick which one YOU (and DW) like the best.

I happen to prefer the Duramax, but a good camping buddy has a Dodge and when I ride in it, it is also a fine rig and has some things I like better than the duramax and things he likes in mine better than the Dodge. Likewise for the neighbor that has a new Ford with the scorpion engine.

Or son get a new work truck every 100K miles or so, has had a dodge, and ford a GM and his personal truck is my old 2004.5 Duramax. He has likes and dislikes about all 3. Depends on what one wants.

Groover wrote:

Grit dog wrote:

SidecarFlip wrote:
I like them all so long as they smoke....

I'll drink to that! Roll coal brotha!

I sincerely hope that you too are joking. I was raised that when something I do offends others I needed to reconsider my ways, especially if that is the only reason for doing it.

Well if you think I’m (anyone ) is doing it just to offend you, you’re placing far too much self importance on the situation.
I was serious btw. I don’t go around intentionally blacking out intersections and rollin coal on people standing at the crosswalk, but your opinion of it is of little, make that no concern to me.