Cummins 6.7L Gasoline Engine in a Ram?

[ShinerBock]

Haven't been on this forum in a while so I am not sure if this has been discussed in the past few months.

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 propane, 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 on one of these fuels only and not just diesel.

These engines will share 80% of their parts. From the head down these engines will be mostly the same 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 with its fuel-agnostic strategy 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 in a 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 6.7-liter gas engine part of new fuel agnostic strategy

[ShinerBock]

I don't think this thing has to create as much horsepower as the naturally aspirated engines. Just look at the 3.5L Ecoboost in comparison to the big V8 offerings. When it came out, it only made 365 horsepower and even today it makes 375 hp yet it can out tow or keep up with the 400+ hp V8's especially at altitude. Heck, the 365 hp version was even very close to the 420 hp 6.2L in the GM in an unloaded 0-60 sprint at sea level in every test of these two engines.

So it wouldn't have to make as much peak horsepower as the V8's as long as it is making more low end torque(which means more low end horsepower) than the other V8's. With even moderate boost, I would wager that this engine could make 600 lb-ft at 2,500 rpm which equates to 285 hp at that rpm. Adversely the Ford 7.3L makes about 450 hp at 2,500 which equates to 215 hp at that rpm. That 60 hp difference at that low rpm is a huge deal especially when you are towing. Will it use more fuel at this rpm, of course, because it is making more power than the 7.3L and more power means more fuel used.

The other thing that people don't discuss when talking peak horsepower numbers is that those numbers are way out in the rpm range where it can only be used in the lower gears which limits the speed you have to be at to use that peak horsepower. Also, for most transmissions, if you are in that higher rpm range for peak horsepower in higher gears, then the torque converter is unlocked(since being locked would put the engine out of its rpm range) meaning you aren't sending all that peak horsepower to the wheels and most of that power is being converted to heat in the torque converter.

For a towing application, I would take more low end torque at an rpm where the horsepower is usable in more gears than 50-75 more horsepower above 5,000 rpm where the horsepower is only usable in lower gears.

[ShinerBock]

larry barnhart wrote:
good to have you back shiner. chevman

Thank you, sir!

[C_Schomer]

The Cummins B and C engines were developed in the 70s for multifuel Third World tractor engines. They built them so stout because they didn’t know what kind of crappy fuel would be used in them. This is far from new territory for Cummins.
50 more years of technology will be interesting to see. Craig

[blt2ski]

Sounds like what International did back in the day. But opposite. Their gas V8 motors were test mukes per say for when they would then turn into diesels.
The IDI 6.9/7.3 iirc was an MV404/443. The small version blew up gas cranks, but did well as a diesel.
Toyota did something similar with some 4 bangers in the past too.
As noted, being as some parts are a bit heavier duty, in some commercial applications, ie an MDT, generator, tractor etc, this design of a motor can make sense. It might not make sense in the light duty truck market.
On the other hand, an I4 version in the class 2B/3 truck relm could work well.

Marty

[rjstractor]

Bionic Man wrote:

rjstractor wrote:

Bionic Man wrote:
How would it not burn more fuel when it has twice the displacement?

When I mentioned "naturally aspirated engines in pickups", I was referring to the V8s used in HD pickups produced by Ford, Stellantis and GM. Those engines are all roughly the same size as the 6.7L B-series Cummins, not twice the displacement. A modern engine's fuel usage is based more on power output, not displacement, especially under high loading. We'll have to wait and see what the specs end up being on these new engines. If they are less fuel efficient than the current gas pickup engines they will fail.

That still doesn’t make sense to me. Adding a turbo effectively increases displacement. When the turbo is spooling it would absolutely use more fuel than a NA similarly sized engine.

I guess the Cummins engineers will have to sort that out if they want this engine to succeed. 😉

[Bionic_Man]

rjstractor wrote:

Bionic Man wrote:
How would it not burn more fuel when it has twice the displacement?

When I mentioned "naturally aspirated engines in pickups", I was referring to the V8s used in HD pickups produced by Ford, Stellantis and GM. Those engines are all roughly the same size as the 6.7L B-series Cummins, not twice the displacement. A modern engine's fuel usage is based more on power output, not displacement, especially under high loading. We'll have to wait and see what the specs end up being on these new engines. If they are less fuel efficient than the current gas pickup engines they will fail.

That still doesn’t make sense to me. Adding a turbo effectively increases displacement. When the turbo is spooling it would absolutely use more fuel than a NA similarly sized engine.

[rhagfo]

The biggest issue I see with making the 6.7 a gas engine is moving mass! It is a big bore, long stroke engine. Not really designed to turn high rpm’s needed to produce HP and Torque.

[rjstractor]

Bionic Man wrote:
How would it not burn more fuel when it has twice the displacement?

When I mentioned "naturally aspirated engines in pickups", I was referring to the V8s used in HD pickups produced by Ford, Stellantis and GM. Those engines are all roughly the same size as the 6.7L B-series Cummins, not twice the displacement. A modern engine's fuel usage is based more on power output, not displacement, especially under high loading. We'll have to wait and see what the specs end up being on these new engines. If they are less fuel efficient than the current gas pickup engines they will fail.

[Bionic_Man]

rjstractor wrote:

FishOnOne wrote:

Bionic Man wrote:
Wouldn’t the fuel economy of a 6.7 turbo gas engine make almost unaffordable?

Maybe it doesn't have a turbo.

I would think it would have to be turbocharged to achieve power levels comparable to current naturally aspirated gas engines used in pickups. Otherwise it will have to be able to run at 5500 rpm or more. Maybe a Cummins B can do that but I doubt it. JMO, but I think it will be direct-injected and have smallish twin turbos. It will rev higher and have less torque than the diesel version, but have the same HP at lower RPM (more torque) compared with current normally aspirated gas V8s. There's no reason it should burn more gas than today's gas engines unless they crank up the boost to try and get 600 hp out of it.

How would it not burn more fuel when it has twice the displacement?

To me, that’s the biggest problem of the gas turbo charged engines. At least the small displacement versions get respectable mpg solo, but put a trailer behind them and they drop like a rock. My ExMAX gets only slightly worse mpg towing my 7000 pound wake boat than my 3000 pound fishing boat.

Towing a 17’ Crestliner at 70 MPH with some wind yesterday I got less than 10 MPG. I can’t imagine what twice the displacement would return.

[rjstractor]

FishOnOne wrote:

Bionic Man wrote:
Wouldn’t the fuel economy of a 6.7 turbo gas engine make almost unaffordable?

Maybe it doesn't have a turbo.

I would think it would have to be turbocharged to achieve power levels comparable to current naturally aspirated gas engines used in pickups. Otherwise it will have to be able to run at 5500 rpm or more. Maybe a Cummins B can do that but I doubt it. JMO, but I think it will be direct-injected and have smallish twin turbos. It will rev higher and have less torque than the diesel version, but have the same HP at lower RPM (more torque) compared with current normally aspirated gas V8s. There's no reason it should burn more gas than today's gas engines unless they crank up the boost to try and get 600 hp out of it.

[FishOnOne]

Bionic Man wrote:
Wouldn’t the fuel economy of a 6.7 turbo gas engine make almost unaffordable?

Maybe it doesn't have a turbo.

[Bionic_Man]

Wouldn’t the fuel economy of a 6.7 turbo gas engine make almost unaffordable?

[FishOnOne]

ShinerBock wrote:

Cummins12V98 wrote:
My question who would buy such an expensive Gas Engine???

With today's prices, I am not surprised anymore on what people will pay for stuff. Many will lay down $11k to go from a base trim package to a premium without batting an eye.

Although I don't think this would be nearly as expensive as the Cummins diesel. You would not need a lot of the emissions equipment which would reduce a lot of cost and weight. You would also not need iron heads, a VG turbo, as large of an EGR and fuels system. So there could be a lot of cost and weight savings in a gas version.

It sounds like there's a lot of common parts on these engine configurations so there was engineering cost savings, tooling savings, and I suspect all these engine configurations will be produced on the same assembly line as the diesel engine so that should equate to more savings.

So overall less investment and operations costs to bring these engine configurations to the market should mean a less expensive engine.

[FishOnOne]

Just another example for the future of diesel.

[thomas201]

I bought a herd of Kubota diesel engines converted to casing head gas, to power pump jacks on oil wells. Honda gasoline engines just self destructed. They did not have enough cooling in the heads. They were designed with the evaporation of gasoline in mind for some cooling. If your ran them at max horsepower, they just could not cut it.

So, they might have a market, but I don't think it would be real big. Interesting though, assuming you get Cummins support. Would truck owners buy a gas engine, at diesel engine prices???