It appears that Cummins is doing the same thing to their 6.7L engines that they have been doing with the larger on highway engines for the past few years by making a performance version and an efficient version of the same engine. The performance versions of their engines have higher power levels at the expense of lower compression ratio to keep NOx levels within standards. The efficient versions generally have higher compression ratios at the expense of power. For those that do not know, compression ratio has a direct correlation with an engines efficiency and how much NOx it produces at a given power output. Essentially the more power you produce, the more NOx you create so to combat this you have to lower compression ratio which reduces efficiency. With the 2019 Cummins, the 400 hp "performance" version with the Aisin comes with a 16.2:1 compression ratio(down from 17.3:1 from 2007-2018) while the 370 hp "efficient" version with the 68RFE comes with a 19.0:1 compression ratio. However, it appears Ram is not calling them performance or efficient version like Cummins does with their other engines. There are no official reviews on the fuel mileage difference, but I would wager it is around a 1-2 mpg(could be more) difference between the two which is similar to the difference percentage wise in the larger engines. Maybe Ram/Cummins is finally listening to many people here who have stated that these trucks make plenty of power for what the average consumer tows, and to start focusing on making the engine more efficient instead of increasing power/towing ratings at the expense of efficiency. What do you think? If you had a choice and towed less than 20k lbs, would you choose the 400 hp/1,000 lb-ft performance version at the expense of 1-2 mpg or go with the 370 hp/850 lb-ft at the expense of 30 hp and 150 lb-ft and higher than 20k tow rating?

All hinges on the fluctuating price of fuel. With the current trend of states jacking up fuel taxes (especially on diesel) to finance their dwindling coffers, 1-2 mpg might become a big deal down the road.

I'd take the more efficient option. My Cummins is rated 370/800 and I've never encountered a situation where I thought I needed any additional power.

I would take the efficiency one as well and just modify and tune it for more power afterwards to get the best of both worlds. If Ram added the 8HP to the efficient version then I would be very tempted to sell mine and get one. I would love to see the fuel mileage that thing gets deleted.

IdaD wrote:I'd take the more efficient option. My Cummins is rated 370/800 and I've never encountered a situation where I thought I needed any additional power.Mine is rated at 325/610 and I certainly could use more going up the Rockies. It just creates heat an wear though; probably safer to back it down.I'd buy the more efficient option. A 10% hit in power is nothing. Both will do the job, one will just do it faster.

ShinerBock wrote:It appears that Cummins is doing the same thing to their 6.7L engines that they have been doing with the larger on highway engines for the past few years by making a performance version and an efficient version of the same engine. The performance versions of their engines have higher power levels at the expense of lower compression ratio to keep NOx levels within standards. The efficient versions generally have higher compression ratios at the expense of power. For those that do not know, compression ratio has a direct correlation with an engines efficiency and how much NOx it produces at a given power output. Essentially the more power you produce, the more NOx you create so to combat this you have to lower compression ratio which reduces efficiency. With the 2019 Cummins, the 400 hp "performance" version with the Aisin comes with a 16.2:1 compression ratio(down from 17.3:1 from 2007-2018) while the 370 hp "efficient" version with the 68RFE comes with a 19.0:1 compression ratio. However, it appears Ram is not calling them performance or efficient version like Cummins does with their other engines. There are no official reviews on the fuel mileage difference, but I would wager it is around a 1-2 mpg(could be more) difference between the two which is similar to the difference percentage wise in the larger engines. Maybe Ram/Cummins is finally listening to many people here who have stated that these trucks make plenty of power for what the average consumer tows, and to start focusing on making the engine more efficient instead of increasing power/towing ratings at the expense of efficiency. What do you think? If you had a choice and towed less than 20k lbs, would you choose the 400 hp/1,000 lb-ft performance version at the expense of 1-2 mpg or go with the 370 hp/850 lb-ft at the expense of 30 hp and 150 lb-ft and higher than 20k tow rating?Interesting that you post this today, as a lunch today at our Veteran's Habitat for Humanity build I was sitting next to a guy that has a 2016 2500 RAM and he quoted non towing best mileage numbers 1-2 MPG better than my 2015 3500 HO gets. Chris

Performance/Efficiency versions of Cummins 6.7L

FishOnOne
Nomad
Jul 06, 2019
That's interesting cummins didn't update their part numbers yet. I wonder if they updated the part numbers for their short block or long block yet.
ShinerBock
Explorer
Jul 06, 2019
FishOnOne wrote:
ShinerBock wrote:
Travlingman wrote:
ShinerBock wrote:
FishOnOne wrote:
ShinerBock wrote:
Both engines can easily and reliably make well over factory power levels

I hear this statement from time to time but I have to ask why did Cummins change the internals to handle the 1,000 ft/lbs. I would have expected no internal changes if this were true.

What internals were changed? My Cuumins Quckserve shows the same internals. The main thing that changed was a CGI block to shave weight and a CP4 to increase fuel pressure to allow more power while meeting emissions. CGI blocked allows you to use less material due to it being a stronger material pound for pound so less can be used while having the same strength similar to how less "high strenght" material is being used in the frames.

The other reason for these changes may also be for future performance gains similar to how Cummins made to the 5.9L and 6.7L over the years by only changing engine tuning, fuel systems, heads, and turbo without changing any internals.

If it wasn't for these emissions requirements and future CAFE regulations coming to HD trucks that are bring mpg requirements to these truck classes. There are plenty of current 6.7L engines making well over 1,000 lb-ft with hundreds of thousands of miles on the clock.

Here are some changes according to their press release:

The new Cummins I6 is now 60 lbs lighter than before, according to Ram. A new cast-iron cylinder head includes new exhaust valves and springs, and new rocker arms. Pistons are redesigned and include new low-friction rings and connect to the crankshaft via newly design forged connecting rods and new bearings. An all-new exhaust manifold houses an improved variable-geometry turbocharger that can deliver up to 33 psi of boost pressure.
New Ram

I show the same part numbers on my Quickserve when comparing a 2016 engine serial number to a 2019 engine serial number on everything under the head(which is what is classified as internals) aside from the block. Any changes made was to reduce internal friction to decrease parasitic engine losses, not to increase strength to handle the added power.

As I told Roy in our other debate, the internals of the 6.7L can and has handled more than 1,000 lb-ft torque that the Ram puts out even in other stock applications. One example is the marine version of the 6.7L that shares the exact same internals and puts out 550 hp/1,250 lb-ft.

Also, the 6.7L computer controlled turbo has always been able to deliver up to 33 psi and can deliver even more, but the stock tune would not allow it to go that high.

According to Lead Engineer - Cummins Truck Engines quite a bit has changed to support the 1000ft/lbs upgrade:
1. CGI block
2. Stronger crank shaft
3. Stronger connecting rods
4. Stronger main bearing caps with larger bolts
5. Stronger flex plate
6. Larger piston wrist pin

Link

According to my Quickserve, the part numbers are to same which they will generally change part numbers if anything has been changed.

Also, the 2018 and below internals already handles well over 1,000 lb-ft(1,250 lb-ft to be exact) in other applications such as the marine version. The only difference between the marine QSB 6.7L and the on road ISB 6.7L is injectors, turbo, head, and the lack of EGR. All internals are the same as what is in the pick up truck version.
FishOnOne
Nomad
Jul 06, 2019
ShinerBock wrote:
Travlingman wrote:
ShinerBock wrote:
FishOnOne wrote:
ShinerBock wrote:
Both engines can easily and reliably make well over factory power levels

I hear this statement from time to time but I have to ask why did Cummins change the internals to handle the 1,000 ft/lbs. I would have expected no internal changes if this were true.

What internals were changed? My Cuumins Quckserve shows the same internals. The main thing that changed was a CGI block to shave weight and a CP4 to increase fuel pressure to allow more power while meeting emissions. CGI blocked allows you to use less material due to it being a stronger material pound for pound so less can be used while having the same strength similar to how less "high strenght" material is being used in the frames.

The other reason for these changes may also be for future performance gains similar to how Cummins made to the 5.9L and 6.7L over the years by only changing engine tuning, fuel systems, heads, and turbo without changing any internals.

If it wasn't for these emissions requirements and future CAFE regulations coming to HD trucks that are bring mpg requirements to these truck classes. There are plenty of current 6.7L engines making well over 1,000 lb-ft with hundreds of thousands of miles on the clock.

Here are some changes according to their press release:

The new Cummins I6 is now 60 lbs lighter than before, according to Ram. A new cast-iron cylinder head includes new exhaust valves and springs, and new rocker arms. Pistons are redesigned and include new low-friction rings and connect to the crankshaft via newly design forged connecting rods and new bearings. An all-new exhaust manifold houses an improved variable-geometry turbocharger that can deliver up to 33 psi of boost pressure.
New Ram

I show the same part numbers on my Quickserve when comparing a 2016 engine serial number to a 2019 engine serial number on everything under the head(which is what is classified as internals) aside from the block. Any changes made was to reduce internal friction to decrease parasitic engine losses, not to increase strength to handle the added power.

As I told Roy in our other debate, the internals of the 6.7L can and has handled more than 1,000 lb-ft torque that the Ram puts out even in other stock applications. One example is the marine version of the 6.7L that shares the exact same internals and puts out 550 hp/1,250 lb-ft.

Also, the 6.7L computer controlled turbo has always been able to deliver up to 33 psi and can deliver even more, but the stock tune would not allow it to go that high.

According to Lead Engineer - Cummins Truck Engines quite a bit has changed to support the 1000ft/lbs upgrade:
1. CGI block
2. Stronger crank shaft
3. Stronger connecting rods
4. Stronger main bearing caps with larger bolts
5. Stronger flex plate
6. Larger piston wrist pin

Link
wilber1
Explorer
Jul 05, 2019
wilber1 wrote:
mich800 wrote:
wilber1 wrote:
ShinerBock wrote:
Cummins12V98 wrote:
I will bet towing them side by side they will get similar mileage. No way 1-2 mpg different. Running solo maybe.

The larger efficiency engines get better fuel mileage than the performance versions even when towing. An engine with a higher compression ratio will be more efficient than the same engine with a lower compression ratio at all engines speeds and loads due to its higher thermal efficiency.

This higher efficiency is represented as a percentage so a 20% increase for example of a higher number will be be greater numerically than a 20% increase of a lower number. For example, a 20% increase of 15 mpg is 18 mpg while a 20% increase of 10 mpg is 12 mpg.

Nissan's variable compression ratio engine uses high compression/low boost for economy and switches to low compression/ high boost for power.

Googled it. Looks like it changes the stroke. Looks complicated. What is the durability track record in a high performance application?

Looks complicated but it depends on how well it is engineered and assembled. Today's engines in general are far more complex than those of 30 years ago, make much more power for their size and are much more reliable to boot.
wilber1
Explorer
Jul 05, 2019
mich800 wrote:
wilber1 wrote:
ShinerBock wrote:
Cummins12V98 wrote:
I will bet towing them side by side they will get similar mileage. No way 1-2 mpg different. Running solo maybe.

The larger efficiency engines get better fuel mileage than the performance versions even when towing. An engine with a higher compression ratio will be more efficient than the same engine with a lower compression ratio at all engines speeds and loads due to its higher thermal efficiency.

This higher efficiency is represented as a percentage so a 20% increase for example of a higher number will be be greater numerically than a 20% increase of a lower number. For example, a 20% increase of 15 mpg is 18 mpg while a 20% increase of 10 mpg is 12 mpg.

Nissan's variable compression ratio engine uses high compression/low boost for economy and switches to low compression/ high boost for power.

Googled it. Looks like it changes the stroke. Looks complicated. What is the durability track record in a high performance application?

Looks complicated but it depends on how well it is engineered and assembled. Today's engines in general are far more complex than those of 30 years ago, make much more power for their size, and are much more reliable to boot.
mich800
Explorer
Jul 05, 2019
wilber1 wrote:
ShinerBock wrote:
Cummins12V98 wrote:
I will bet towing them side by side they will get similar mileage. No way 1-2 mpg different. Running solo maybe.

The larger efficiency engines get better fuel mileage than the performance versions even when towing. An engine with a higher compression ratio will be more efficient than the same engine with a lower compression ratio at all engines speeds and loads due to its higher thermal efficiency.

This higher efficiency is represented as a percentage so a 20% increase for example of a higher number will be be greater numerically than a 20% increase of a lower number. For example, a 20% increase of 15 mpg is 18 mpg while a 20% increase of 10 mpg is 12 mpg.

Nissan's variable compression ratio engine uses high compression/low boost for economy and switches to low compression/ high boost for power.

Googled it. Looks like it changes the stroke. Looks complicated. What is the durability track record in a high performance application?
mich800
Explorer
Jul 05, 2019
wilber1 wrote:
ShinerBock wrote:
Cummins12V98 wrote:
I will bet towing them side by side they will get similar mileage. No way 1-2 mpg different. Running solo maybe.

The larger efficiency engines get better fuel mileage than the performance versions even when towing. An engine with a higher compression ratio will be more efficient than the same engine with a lower compression ratio at all engines speeds and loads due to its higher thermal efficiency.

This higher efficiency is represented as a percentage so a 20% increase for example of a higher number will be be greater numerically than a 20% increase of a lower number. For example, a 20% increase of 15 mpg is 18 mpg while a 20% increase of 10 mpg is 12 mpg.

Nissan's variable compression ratio engine uses high compression/low boost for economy and switches to low compression/ high boost for power.

Interesting, how to they vary compression?
wilber1
Explorer
Jul 05, 2019
ShinerBock wrote:
Cummins12V98 wrote:
I will bet towing them side by side they will get similar mileage. No way 1-2 mpg different. Running solo maybe.

The larger efficiency engines get better fuel mileage than the performance versions even when towing. An engine with a higher compression ratio will be more efficient than the same engine with a lower compression ratio at all engines speeds and loads due to its higher thermal efficiency.

This higher efficiency is represented as a percentage so a 20% increase for example of a higher number will be be greater numerically than a 20% increase of a lower number. For example, a 20% increase of 15 mpg is 18 mpg while a 20% increase of 10 mpg is 12 mpg.

Nissan's variable compression ratio engine uses high compression/low boost for economy and switches to low compression/ high boost for power.
ACZL
Explorer
Jul 05, 2019
Like Tim Taylor from Home Improvement would say..." More Power!" Tho I own a Powerstroke, if I was to go w/Ram, I'd opt for the Aison and biggest Cummins (stock) I could. Just my opinion.
ShinerBock
Explorer
Jul 05, 2019
Travlingman wrote:
ShinerBock wrote:
FishOnOne wrote:
ShinerBock wrote:
Both engines can easily and reliably make well over factory power levels

I hear this statement from time to time but I have to ask why did Cummins change the internals to handle the 1,000 ft/lbs. I would have expected no internal changes if this were true.

What internals were changed? My Cuumins Quckserve shows the same internals. The main thing that changed was a CGI block to shave weight and a CP4 to increase fuel pressure to allow more power while meeting emissions. CGI blocked allows you to use less material due to it being a stronger material pound for pound so less can be used while having the same strength similar to how less "high strenght" material is being used in the frames.

The other reason for these changes may also be for future performance gains similar to how Cummins made to the 5.9L and 6.7L over the years by only changing engine tuning, fuel systems, heads, and turbo without changing any internals.

If it wasn't for these emissions requirements and future CAFE regulations coming to HD trucks that are bring mpg requirements to these truck classes. There are plenty of current 6.7L engines making well over 1,000 lb-ft with hundreds of thousands of miles on the clock.

Here are some changes according to their press release:

The new Cummins I6 is now 60 lbs lighter than before, according to Ram. A new cast-iron cylinder head includes new exhaust valves and springs, and new rocker arms. Pistons are redesigned and include new low-friction rings and connect to the crankshaft via newly design forged connecting rods and new bearings. An all-new exhaust manifold houses an improved variable-geometry turbocharger that can deliver up to 33 psi of boost pressure.
New Ram

I show the same part numbers on my Quickserve when comparing a 2016 engine serial number to a 2019 engine serial number on everything under the head(which is what is classified as internals) aside from the block. Any changes made was to reduce internal friction to decrease parasitic engine losses, not to increase strength to handle the added power.

As I told Roy in our other debate, the internals of the 6.7L can and has handled more than 1,000 lb-ft torque that the Ram puts out even in other stock applications. One example is the marine version of the 6.7L that shares the exact same internals and puts out 550 hp/1,250 lb-ft.

Also, the 6.7L computer controlled turbo has always been able to deliver up to 33 psi and can deliver even more, but the stock tune would not allow it to go that high.

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Performance/Efficiency versions of Cummins 6.7L

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