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 > Ram 2500 CTD and GM 2500 Dmax up the Ike.

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4x4ord

Alberta

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Posted: 06/16/21 07:46am Link  |  Quote  |  Print  |  Notify Moderator

Bionic Man wrote:

If the standard output Cummins was able to maintain speed, wouldn't it be reasonable to assume that the HO Cummins would use a similar amount of fuel, as it would not need to make more power to do the same speed?

Honestly I'm surprised these trucks are able to do those speeds up the hill. My 350/800 Cummins won't pull my 12,000 pound 5er eastbound to the tunnel at the speed limit. I'm somewhere between 35-40 MPH at the very top. My best friend's 2013 PSD pulling a very similar trailer is the exact same. Does the higher profile of the RV really make that much of a difference?


At 40 mph the added wind drag that might be on a 12000 lb high profile fiver is negligible compared to a 12000 lb equipment trailer. At 75 mph the difference in drag might be a factor. When you’re foot to the floor doing 35 - 40 mph your using all the power your engine can make and yet the power required to overcome drag at that speed is going to fall between 30 and 40 hp no matter what kind of trailer your pulling.


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Groover

Pulaski, TN

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Posted: 06/16/21 08:28am Link  |  Quote  |  Print  |  Notify Moderator

4x4ord wrote:

Bionic Man wrote:

If the standard output Cummins was able to maintain speed, wouldn't it be reasonable to assume that the HO Cummins would use a similar amount of fuel, as it would not need to make more power to do the same speed?

Honestly I'm surprised these trucks are able to do those speeds up the hill. My 350/800 Cummins won't pull my 12,000 pound 5er eastbound to the tunnel at the speed limit. I'm somewhere between 35-40 MPH at the very top. My best friend's 2013 PSD pulling a very similar trailer is the exact same. Does the higher profile of the RV really make that much of a difference?


At 40 mph the added wind drag that might be on a 12000 lb high profile fiver is negligible compared to a 12000 lb equipment trailer. At 75 mph the difference in drag might be a factor. When you’re foot to the floor doing 35 - 40 mph your using all the power your engine can make and yet the power required to overcome drag at that speed is going to fall between 30 and 40 hp no matter what kind of trailer your pulling.


That does seem to be awfully slow. I went through the pass a few years ago in my motorhome equipped with 300/600 detuned Cummins and running about 28,000lbs GCWR. I may not have been doing the speed limit but I don't remember being particularly slow either.

Cummins12V98

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Posted: 06/16/21 09:13am Link  |  Quote  |  Print  |  Notify Moderator

Groover wrote:

14-3" high?!

My motorhome is 17" shorter and I have to dodge things with it on back roads fairly often. And that is a LOT of air drag. I don't understand why they don't make low side pickup beds for 5ers so that the front room can be lowered. Every inch counts when you are that high.


Oops dang dyslexic tendencies. 13'-4"


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BackOfThePack

Fort Worth

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Posted: 06/24/21 04:56am Link  |  Quote  |  Print  |  Notify Moderator

Faster in the quarter-mile than my ‘04?

Higher “Average MPG” than against same?

Faster braking 60-0 than against same?

3rd Gen trucks were grossing combined-rig 32K-lb in oilfield hotshot loads for 300k mile service (lease roads more than just “difficult), so today’s aren’t really towing more.

OTOH, a MY-2022 semi tractor gets significantly better MPG & HP from an engine of the same displacement than the MY-2005 version. Software, tires and aero have all improved. Tractor isn’t lighter, has genuine comfort improvements.

— Higher pickup sales price with no significant compensatory improvements in 17-years.

— Per-mile average diesel pickup ownership/operational costs (CPM) went thru the roof over this period.

— Doesn’t do more work in total — nor does the same at a lower cost.

But it matters a trivially stupid grade ascent speed test?


.

* This post was edited 06/24/21 05:14am by BackOfThePack *


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wintersun

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Posted: 06/24/21 04:38pm Link  |  Quote  |  Print  |  Notify Moderator

Not a good test at all by these fellows. Far better are the ones done by mrtrailer.com where all aspects are evaluated. A key reason for paying for a diesel engine is the availability of the exhaust brake and how effective and easy this key feature is depends on the manufacturer.

Good example of a good testing evaluation is this one from 2011
https://mrtrailer.com/puchurtlocker2.htm

There are also differences under the skin that the approach of these guys ignores completely. For example the frame of the 2500/3500 Chevy trucks was made much stronger for their 2011 and later trucks but Ram did not do this until 2013 for their 3500 trucks and not until 2014 for their 2500 trucks. Ford did not increase the strength of their heavy duty truck frames until 2016.

Engine reliability also varies from make to make and from year to year and who wants the "best" truck in a test when later they find that it is requiring frequent or very expensive repairs to keep it on the road.

Also towing features are changing greatly year to year including special modes for backing up a trailer, trailier TPMS, and multiple cameras and crash avoidance with coverage of the lanes on the sides of the trailer in addition to that of the truck. Ford appears to be ahead as of 2020 but no telling what will be available in the 2022 models from the big three pickup manufacturers.

Factory trailer brake controllers vary from one make to the next and some are great and others are not purchased as their owners prefer third party ones.

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