Difference in Engine? : Ram 850 ft.lb. 3500 vs. 800 ft lb. Torque 2500

[cooperns1943]

I am rephrasing this question previously submitted for possible better clarity. When I shopped last year for my new truck, comparing 2015 Ram 2500 6.7L vs 2015 Ram 3500 6.7L it seemed I could not get clear answers from the dealerships. What differences have been made to the engine of the 850 ft. lb. torque HP Ram 3500 vs. the 800 ft. lb. torque Ram 2500? Could it be difference in computer programming of the engine or a larger turbo, or higher rate of the injectors or a combination? After driving both trucks I feel very little difference. Appreciate knowledgeable responses.

 

[SnoKing]

Just computer programming I believe, however it is not the torque difference, but the transmission(Aisin) used behind the 850 engine that is the real difference. Snoking

 

[Bob V]

The Aisin is advertised as a more efficient transmission than the 68RFE so at least some of the extra torque will be from less power loss through the transmission. I believe nether trans will give full torque until 4th (direct) gear. It might not be immediate power increase but slowly add power to protect the drivetrain. In a way, the full computer control on the new engines give the manufacturer lots of ways to "cheat" output ratings.

 

[SnoKing]

Factory torque and HP ratings are at the crank! So the transmission does not play into the higher rating. Snoking

 

[Joseph Donnelly]

Agreed, ratings are at the crankshaft. Also Cummins told us during the 2013 plant tour that the difference in ratings comes from software in the ecm. Mechanically the engines are the same, coated piston skirts, etc. Freightliner engines don't have the coated pistons.

 

[SnoKing]

Also, maybe someone knows the paralytic loss for the Aisin and the 68RFE? I would think they are similar. SNOKING

 

[AH64ID]

Programming.

A larger turbo isn't needed since there is only a small hp difference in the upper rpms where airflow would be a bigger issue.

15hp at 2800 rpms is only 28 ft/lbs different at rated rpm.
65 ft/lbs at 1700rpm is 21hp more on the HO.

As you can see the difference isn't all the much hp, just makes a difference in ratings at useable rpms.

 

[SnoKing]

If the truth is known, it might have been as simple as removing a little torque management!

 

[AH64ID]

If the truth is known, it might have been as simple as removing a little torque management!

I don't think so, torque management is a different beast altogether.

 

[rynosback]

The 2015 3500 TD Aisin is rated at 865. It was 850 in 2014 and then the remapped the turbo and fuel system.
Pair an available AISIN six-speed heavy-duty automatic transmission with our available 6.7L Cummins® Turbo Diesel I6 engine and benefit from our Best-in-Class 865 pound-feet of torque+.

 

[Jim W]

Also, maybe someone knows the paralytic loss for the Aisin and the 68RFE? I would think they are similar. SNOKING

When I worked at Caterpillar we always used 20% loss of engine crank HP and LB-FT of torque through the powertrain components to calculate usable HP and torque for the hydraulic pump drives and wheel HP and LB-Ft of torque for draw bar pull.

This is what I always have use also on my truck to figure out what the rear wheel HP and LB-FT of torque is. I have never put the truck on a dynamometer to double check the numbers but this is close.

Jim W.

 

[AH64ID]

My NV5600 had a 15% drop when I dyno'd it. I have heard similar numbers for a auto with the tq converter locked.