Cummins 6.7L Gasoline Engine in a Ram?

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SouthTexan

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Back In February, Cummins unveiled their new fuel-agnostic strategy meaning that various engines in their line-up can be spec'd for different fuel types like natural gas, hydrogen, and yes even gasoline. To clarify, that doesn't mean that one engine can run on all of these fuel sources, but rather you can have them spec'd to run one of these fuels only and not just diesel.

From the head down, these engines will have most of the same parts as the current Cummins diesel. From the head up you will have different parts to for the various fuel types along with different fuel and air delivery systems. So essentially you will have the same reliable diesel engine components, but in gasoline form.

They said that the B6.7L will be the first to be offered in 2024. Medium duty customers will be able to spec the B6.7L to run on gasoline. I am not sure what plans Ram has for the 6.4L, but I would love to see a gasoline powered Cummins 6.7L turbo Ram HD. Not sure how they will handle the heat associated with gasoline turbo engines.

What do you think?

Cummins unveils fuel-agnostic internal combustion engine strategy

Cummins fuel-agnostic.png
 
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SouthTexan

SouthTexan

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True, but you would be able to cut quite a bit of weight an a gasoline version. The new CGI block weighs a good deal less than the old iron block bringing the current weight down to 1,070 lbs..

With a gas version you wouldn't need an iron head that the diesel uses and can use mostly aluminum which would be even more weight gone. The EGR system would be reduced in size dramatically since gas engines do not utilize the EGR system as much as diesels do. More weight savings can come from not needing as large components of the diesel's much higher pressure fuel system. You would not have a VG turbo since they cannot handle the heat of a gas engine so that would take away some of the weight as well. Although Cummins would likely go with a compound turbo set up which would add a little more weight.

All in all, I bet the gas version could be within a 100 lbs. or so from the 750 lbs. of the iron block 6.4L Hemi.

Edit: Apparently the 750 was with the old all iron 392 Hemi. The new aluminum head 6.4L weighs around 500 lbs. Man we have come a long way in weight reduction.
 
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68PowerWagon

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Oh ST what do you know about Cummins? :rolleyes: Just kidding :Big Laugh: The big issue I see there is that there is a certain party that does not want to see any of these on the roads except maybe the hydrogen. I mean I am all for some electric vehicles, the torque will be phenomenal. But our grid & infrastructure is no where near ready to take on all these electrics they want on the road. The hydrogen really peeks my interest. But I don't think we are no where near ready to have a bunch of those rolling around by 2030 either. Can those X15's put out as much HP & torque as the Cat 15? Are they pretty close in reliability? I have always heard the C15 is bad momba jomba!
 
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SouthTexan

SouthTexan

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Oh ST what do you know about Cummins? :rolleyes: Just kidding :Big Laugh: The big issue I see there is that there is a certain party that does not want to see any of these on the roads except maybe the hydrogen. I mean I am all for some electric vehicles, the torque will be phenomenal. But our grid & infrastructure is no where near ready to take on all these electrics they want on the road. The hydrogen really peeks my interest. But I don't think we are no where near ready to have a bunch of those rolling around by 2030 either. Can those X15's put out as much HP & torque as the Cat 15? Are they pretty close in reliability? I have always heard the C15 is bad momba jomba!


Currently, the max rating on the X15 is 605 hp. If my memory serves me right, the max rating on a C15 was 625 hp. The C15 was a dirty engine in regards to emissions and one of the reasons why it was able to achieve higher power numbers compared to Cummins. This is also the reason why they exited the on-highway market in 2010 because it would have taken a lot of time and money to get their engines inline with the 2010 emissions spec which would also decrease the reliability for several years until they worked the bugs out like most manufacturers had to do for the first years after the new emissions standards.

My company still sells millions of dollars of Cat parts even though they haven't made an on-highway engine in over 10 years. They are still a significant vendor of ours; behinds Cummins of course.
 

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What do you think the power output on a B6.7 gas version would be?
 
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SouthTexan

SouthTexan

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What do you think the power output on a B6.7 gas version would be?


My bet would be above 400 hp if it revs above 4,500 rpm and 600 lb-ft at around 2,500 rpm. Keep in mind that while that is less hp than the N/A V8's, a turbocharged engine does not need to make as much peak horsepower to have the same if not better performance as N/A engines. Case in point is the Ford 3.5L Ecoboost that made 365 hp back when it came out and was neck and neck with the 420 hp GM 6.2L in 0-60 sprints unloaded in every truck review and even out performed it in several towing tests especially at higher elevations.
 

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B6.7 Gasoline or Hurricane Inline-6 Twin-Turbo?
Cost vs profit. External supply vs internal supply.
 

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....

All in all, I bet the gas version could be within a 100 lbs. or so from the 750 lbs. of the iron block 6.4L Hemi.

Edit: Apparently the 750 was with the old all iron 392 Hemi. The new aluminum head 6.4L weighs around 500 lbs. Man we have come a long way in weight reduction.

And the 6.4 HEMI weight can be reduced further if the block went from cast iron to CGI.
 
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SouthTexan

SouthTexan

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B6.7 Gasoline or Hurricane Inline-6 Twin-Turbo?
Cost vs profit. External supply vs internal supply.

That depends on whether you can pass the costs to the market like they do with the diesel Cummins. If customers will pay a higher premium due to the Cummins brand(like most due for other brands), then you can defiantly make more profit with the Cummins. A gas Cummins will definitely not cost or weigh as much as the Cummins diesel. Also, I don't think a 3.0L inline 6 will last long in an HD pickup's duty cycle so that engine is likely out for the 2500 and up trucks.
 

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My bet would be above 400 hp if it revs above 4,500 rpm and 600 lb-ft at around 2,500 rpm. Keep in mind that while that is less hp than the N/A V8's, a turbocharged engine does not need to make as much peak horsepower to have the same if not better performance as N/A engines. Case in point is the Ford 3.5L Ecoboost that made 365 hp back when it came out and was neck and neck with the 420 hp GM 6.2L in 0-60 sprints unloaded in every truck review and even out performed it in several towing tests especially at higher elevations.
Tried looking up what would be even projected, didn't find anything. HP isn't everything, torque coming on lower in the RPM band would be pretty sweet.

I would be interested in one of these when they come out. Especially towing in a HD truck if the torque numbers come on at a lower RPM. Not b!tc#!n about the 6.4Hemi, it does good.
 
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SouthTexan

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And the 6.4 HEMI weight can be reduced further if the block went from cast iron to CGI.

You could, but that would also increase cost. Another thing to note that would also increase future cost with the 6.4L is homologation of their different platforms. The reason why certain vehicle manufacturers only create V engines and others(BMW) mostly only create inline engines in certain models, is because it is easier and cost effective to design the vehicles and your engine plants around one engine design.

Having to design different engine bays, driveline setups, and factories for each configuration is costly. If Ram is going to put only these inline 6 3.0L engines in their 1500's and the engine bays of these trucks(both 1500 and HD) are designed for inline engines, then it would be cost effective for them to have all inline engines in their line-up.
 

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That depends on whether you can pass the costs to the market like they do with the diesel Cummins. If customers will pay a higher premium due to the Cummins brand(like most due for other brands), then you can defiantly make more profit with the Cummins. A gas Cummins will definitely not cost or weigh as much as the Cummins diesel. Also, I don't think a 3.0L inline 6 will last long in an HD pickup's duty cycle so that engine is likely out for the 2500 and up trucks.

The gas Cummins does weigh as much as the diesel. The block is the same, the head is modified. They're not gonna cast a unique block and head for low production volume. I worked at Cummins 22 years.
 

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And the 6.4 HEMI weight can be reduced further if the block went from cast iron to CGI.

Not much. CGI only takes the graphite in grey cast iron and partially nodularizes it with adding magnesium and heat treatment. Mass is app. Tje same. The would have to cast a new block altogether to use the higher strength and ductility of CGI.
Most of the cost of engines is in the tooling. Esp. blocks and heads.
 
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SouthTexan

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The gas Cummins does weigh as much as the diesel. The block is the same, the head is modified. They're not gonna cast a unique block and head for low production volume. I worked at Cummins 22 years.


I worked for Cummins HQ as well. First in R&D, then if filtration, and finally in power generation before I went to work where I work now which is the worlds largest class 7 & 8 truck dealer group. We still deal heavily with Cummins(over $200M annually and a joint LNG tank venture) and I still have several sales contacts there.

From what I am being told, it is more than jus a modified head. It appears that the head will be aluminum which will have weight savings. There is also no need for such a large EGR system and cooler for gas engines. There are weight savings in the fuel system since the gas version does not need a CP4 pump or the large injectors and lines of the diesel. A much smaller electronic HPFP like almost all direct injected engines have these days will suffice. Then there is the weight of the emissions equipment like the DPF, SCR, and DEF system which weighs A LOT.

Removing all of this will not only cut cost, but also a lot of weight as well. According to Ram's body builder site, the weight difference between the Cummins and 6.4L truck(same tradesman and 6.4 box configuration) is around 850 lbs. Removing all the stuff above would definitely remove at least half of that weight. With as much low end power and torque that a gas turbocharged inline 6 would make, I doubt the possibly 400 lbs difference between the 6.4L and a gas Cummins would be an issue.
 
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nick112288

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So it's the same rotating assembly, gas has slightly less energy than diesel.

What's keeping this 6.7 gas engine from producing near the same hp/tq as the diesel version? I assume compression ratio difference?
 

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I worked for Cummins HQ as well. First in R&D, then if filtration, and finally in power generation before I went to work where I work now which is the worlds largest class 7 & 8 truck dealer group. We still deal heavily with Cummins(over $200M annually and a joint LNG tank venture) and I still have several sales contacts there.

From what I am being told, it is more than jus a modified head. It appears that the head will be aluminum which will have weight savings. There is also no need for such a large EGR system and cooler for gas engines. There are weight savings in the fuel system since the gas version does not need a CP4 pump or the large injectors and lines of the diesel. A much smaller electronic HPFP like almost all direct injected engines have these days will suffice. Then there is the weight of the emissions equipment like the DPF, SCR, and DEF system which weighs A LOT.

Removing all of this will not only cut cost, but also a lot of weight as well. According to Ram's body builder site, the weight difference between the Cummins and 6.4L truck(same tradesman and 6.4 box configuration) is around 850 lbs. Removing all the stuff above would definitely remove at least half of that weight. With as much low end power and torque that a gas turbocharged inline 6 would make, I doubt the possibly 400 lbs difference between the 6.4L and a gas Cummins would be an issue.


Wow - that's pretty wild they're gonna invest in a head unique to gas. Presuming they're using large sales projection forecast to justify all that new tooling.

The block is still the principal weight of the engine, along with the crank and head. Are they going to do an aluminum block, too?
 

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So it's the same rotating assembly, gas has slightly less energy than diesel.

What's keeping this 6.7 gas engine from producing near the same hp/tq as the diesel version? I assume compression ratio difference?

Physics of combustion. You can not ignite a stoichiometric air-fuel mixture until just before the piston reaches top dead center, so you're limited to how much you can jam into the cylinder.

By comparison, a diesel injects fuel in a uniform spray pattern at the same point, and the combustion flame front is more widely spread out (piston crown is bowl-shaped). Before multiple-injection diesel piezo fuel injectors, you had to squirt all the demanded fuel in a single injection. That caused a loud 'rap' as a lot of the fuel ignited simultaneously. Now we have multiple fuel injections per power stroke, such that a small bit of fuel is the pilot ignition that doesn't cause a sharp 'rap'. This starts the flame front, to which more fuel is added with subsequent fuel injections. Modern diesels are incredibly quiet as a result (and expensive as result, too!).

There are such things a gaseous fuel injectors, but last I knew they were quite expensive and only used on large, commercial gas engines on gas line pumping station engines. Otherwise, we're restricted to carbureted gaseous engines, where it's difficult to run lean and rich modes. Anyway, ingesting a flammable mixture can't be ignited until the proper time - which limits how hot you can get it beforehand - otherwise it will pre-ignite from compression heat and/or ambient temperature heat, and/or load heat.

And, of course, the power density of gaseous fuel is much, much lower than diesel fuel.

I probably didn't explain this very well, being a retired engineer.
 

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Physics of combustion. You can not ignite a stoichiometric air-fuel mixture until just before the piston reaches top dead center, so you're limited to how much you can jam into the cylinder.

By comparison, a diesel injects fuel in a uniform spray pattern at the same point, and the combustion flame front is more widely spread out (piston crown is bowl-shaped). Before multiple-injection diesel piezo fuel injectors, you had to squirt all the demanded fuel in a single injection. That caused a loud 'rap' as a lot of the fuel ignited simultaneously. Now we have multiple fuel injections per power stroke, such that a small bit of fuel is the pilot ignition that doesn't cause a sharp 'rap'. This starts the flame front, to which more fuel is added with subsequent fuel injections. Modern diesels are incredibly quiet as a result (and expensive as result, too!).

There are such things a gaseous fuel injectors, but last I knew they were quite expensive and only used on large, commercial gas engines on gas line pumping station engines. Otherwise, we're restricted to carbureted gaseous engines, where it's difficult to run lean and rich modes. Anyway, ingesting a flammable mixture can't be ignited until the proper time - which limits how hot you can get it beforehand - otherwise it will pre-ignite from compression heat and/or ambient temperature heat, and/or load heat.

And, of course, the power density of gaseous fuel is much, much lower than diesel fuel.

I probably didn't explain this very well, being a retired engineer.

I know on a diesel it's more fuel/air equals more power (I know that's an over simplification of modern diesels). Wasn't sure if on a modern electronically controlled forced induction gasoline engine if the same could be accomplished on the fly, to a certain point.

My concern is how something like the heavy, long stroke assembly of the 6.7 would compare to the comparatively lighter and higher reving gas inline 6s and v8s.
 

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I know on a diesel it's more fuel/air equals more power (I know that's an over simplification of modern diesels). Wasn't sure if on a modern electronically controlled forced induction gasoline engine if the same could be accomplished on the fly, to a certain point.

My concern is how something like the heavy, long stroke assembly of the 6.7 would compare to the comparatively lighter and higher reving gas inline 6s and v8s.

Well, if they 6.7 is used with gasoline (not natural gas or propane), it can be run up to the detonation (pre-ignition) point of gasoline. To do that properly requires at least a port fuel injector to run in stoichiometric mode, and a turbocharger / compression ratio combination that takes the combustible mixture just to the point of pre-ignition.

It still wouldn't produce near the torque or power, of course, because gasoline is less energy dense than diesel fuel, and it's propensity to pre-ignition requires a maximum cylinder pressure far lower than that with diesel fuel.
 
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