Cummins 6.7L Gasoline Engine in a Ram?

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

nick112288

Junior Member
Joined
Jul 3, 2022
Posts
5
Reaction score
2
Location
Lawrenceburg, IN
Ram Year
1995
Engine
5.9 Cummins
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.

And that far lower cylinder pressure is why I'm wondering how well a gas with that rotating assembly will actually perform.
 

HEMIMANN

Senior Member
Supporting Member
Military
Joined
Dec 7, 2020
Posts
6,797
Reaction score
17,079
Location
Minneapolis, MN
Ram Year
2017 2500 Laramie Crew Cab
Engine
6.4L HEMI
And that far lower cylinder pressure is why I'm wondering how well a gas with that rotating assembly will actually perform.

Like a gas motor - needs rpm to make up for lack of high cylinder pressure.
 

nick112288

Junior Member
Joined
Jul 3, 2022
Posts
5
Reaction score
2
Location
Lawrenceburg, IN
Ram Year
1995
Engine
5.9 Cummins
Like a gas motor - needs rpm to make up for lack of high cylinder pressure.
Which gets into if the gas engine will be able to spin like it needs.

That rotating assemblies weight and long stroke are a major limiting factor in how fast the 6.7 can spin.

Unless I'm completely wrong and missing something, which I'll gladly admit if you have the answer to whatever I'm missing.
 

HEMIMANN

Senior Member
Supporting Member
Military
Joined
Dec 7, 2020
Posts
6,797
Reaction score
17,079
Location
Minneapolis, MN
Ram Year
2017 2500 Laramie Crew Cab
Engine
6.4L HEMI
Which gets into if the gas engine will be able to spin like it needs.

That rotating assemblies weight and long stroke are a major limiting factor in how fast the 6.7 can spin.

Unless I'm completely wrong and missing something, which I'll gladly admit if you have the answer to whatever I'm missing.

Nope - you're doing good! Which goes back to my point that it's not usually cost-effective to convert a diesel into a sparky. The only reason we did it was for the few applications that wanted a continuous duty engine running on gaseous fuel - hog farm digester, small pipeline pumping station, etc. But there are no mass production users I am aware of.
 

nick112288

Junior Member
Joined
Jul 3, 2022
Posts
5
Reaction score
2
Location
Lawrenceburg, IN
Ram Year
1995
Engine
5.9 Cummins
Nope - you're doing good! Which goes back to my point that it's not usually cost-effective to convert a diesel into a sparky. The only reason we did it was for the few applications that wanted a continuous duty engine running on gaseous fuel - hog farm digester, small pipeline pumping station, etc. But there are no mass production users I am aware of.

Well I'm glad the questions in my head were the right ones!

At first all I could think was this will be awesome and probably blow the other 2 HD gas engines out of the water, then I started thinking wait why hasn't anyone done this before, which lead to how will a gas engine that's considerably less compression produce good power when it can't swing around as fast as a gas needs?

Not saying it won't be an awesome engine, now I'm just not as gungho and already sold on it as I was before.
 
Top