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Open Roads Forum  >  Tow Vehicles

 > Cummins 6.7L Gasoline Engine in a Ram?

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FishOnOne

The Great State of Texas

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Posted: 04/30/22 12:52pm Link  |  Quote  |  Print  |  Notify Moderator

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.


'12 Ford Super Duty FX4 ELD CC 6.7 PSD 400HP 800ft/lbs
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rjstractor

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Posted: 04/30/22 01:31pm Link  |  Quote  |  Print  |  Notify Moderator

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.

Bionic Man

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Posted: 04/30/22 07:02pm Link  |  Quote  |  Print  |  Notify Moderator

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.


2012 RAM 3500 Laramie Longhorn DRW CC 4x4 Max Tow, Cummins HO, 60 gallon RDS aux fuel tank, Reese 18k Elite hitch
2003 Dodge Ram 3500 QC SB 4x4 Cummins HO NV5600 with Smarty JR, Jacobs EB (sold)
2002 Gulf Stream Sea Hawk 29FRB with Honda EV6010

rjstractor

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Posted: 04/30/22 07:23pm Link  |  Quote  |  Print  |  Notify Moderator

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.

rhagfo

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Posted: 04/30/22 07:23pm Link  |  Quote  |  Print  |  Notify Moderator

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.


Russ & Paula the Beagle Belle.
2016 Ram Laramie 3500 Aisin DRW 4X4 Long bed.
2005 Copper Canyon 293 FWSLS, 32' GVWR 12,360#

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Bionic Man

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Posted: 04/30/22 07:54pm Link  |  Quote  |  Print  |  Notify Moderator

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.

rjstractor

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Posted: 05/01/22 09:12am Link  |  Quote  |  Print  |  Notify Moderator

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. [emoticon]

blt2ski

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Posted: 05/01/22 09:41am Link  |  Quote  |  Print  |  Notify Moderator

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


92 Navistar dump truck, 7.3L 7 sp, 4.33 gears with a Detroit no spin
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C Schomer

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Posted: 05/01/22 07:51pm Link  |  Quote  |  Print  |  Notify Moderator

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

ShinerBock

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Posted: 05/02/22 06:35am Link  |  Quote  |  Print  |  Notify Moderator

larry barnhart wrote:

good to have you back shiner. chevman


Thank you, sir!


2014 Ram 2500 CTD
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