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Old 03-25-2014, 06:48 PM   #15
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Quote:
Originally Posted by crewstx View Post
I recently purchased a RAM 3500 DRW with a 3.73 rear end. I am only getting about 14-15 MPG at 65 W/O any load and about 8 MPG towing a Montana fifth wheel on level road. Is this all I should expect. My old 5.9 2007 got about 21 unloaded and 11 MPG pulling the same fifth wheel.

What type of mileage are others getting and what do they have is data I would like to get.

Is there any way to improve the mileage besides trading truck?
was your old 07 a 2500 or SRW 3500 truck? Both would move though the air easier than a Larger heavier Truck.
And what are the power output differences?
There is only so much HP in a gallon of fuel. More HP is more fuel.
is this Montana 5er the one that got you the 11MPG in the old truck?
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Old 03-26-2014, 12:34 AM   #16
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crewstx:

We test drove the early production 2013 RAM 3500 DRW and liked it a lot. They are very nice trucks with great capability and power. We were shopping for a pickup that could handle our 2006 Artic Fox (purchased used) and the way this early 2013 RAM was optioned, it had inadequate payload capability for the camper. We ended up with a 2013 F350 DRW 4X4 CrewCab Camper Package that had plenty of margin on the 4600 lb. payload requirement (I still had to have custom overloads made to get the ride height level - worth every penny). The RAM was otherwise my first choice.

While they are not the same truck, I have discovered the following:

My mileage has improved from 15 unloaded (60 on the level) new to almost 19 in the same conditions with just under 18K on it. Seems the engine gets better with age. This includes the effects of an active regen every 300 miles or so which consumes about 1 quart of diesel to heat the oxygen in the exhaust stream and thereby burn off the accumulated particulate matter (soot). Using cruise control provides the best possible mileage. We get around 12 with camper on, unless it's windy when I've seen single digit numbers.

We've done a lot of research on clean diesels (forgive me for I am a rocket scientist, now retired except for the occasional consulting work) and have turned that research in a small company that we're trying to get off the ground in our retirement, just for fun and entertainment. We are a supporter of the IRV2 forum, and enjoy trying to provide answers to RVer's questions.

Check out our other posts on the subject of DEF, EGR, DPF, and clean diesels for all the details, but here are some things to consider:

The SCR system on all the new diesels (which consume DEF) allow much more efficient combustion (less EGR, higher combustion pressures, MORE BOOST) so in principle they should consume less fuel.

Diesel Particulate Filters DPF have little effect on back pressure, based on seeing the insides of several at the 2013 Diesel Emissions Conference. Turbochargers fully expand the exhaust gas on diesels, resulting in very low static pressures in the exhaust. DPFs are continually improving, and the recent addition of catalysts to make passive regen more effective will use even less diesel to aide combustion of carbon particles in the DPF.

I believe the Cummins in your RAM has active regen similar to the Ford. I also believe it is similar to the Ford in that delayed injection of fuel in the cylinder is used to add heat to the exhaust. This can (in unusual circumstances) result in oil dilution due to washdown in a COLD cylinder.

Chev/GMC Duramax may have come up with a better approach: they added a 9th fuel injector after the turbocharger to add fuel and create heat. Of course it another part that can fail...

Interestingly, the primary culprit in DPF long term life is the residual engine lubricating oil in the cylinder that burns with the diesel. The particulate matter from lubricating oil combustion does not burn off well in the DPF, and converts to ash. Using the oil specified in the owner's manual (low ash causing content) can be important to DPF life.

I'm kind of a half full glass kind of person (especially if it a Red Solo cup with a nice beverage in it which reminds me it's time for a refill) so here is my closing thought on the subject:

The new trucks are INCREDIBLE: quiet, capable, and powerful, easily driven with amazing safety features, and have had 93-98% of the particulate matter and NOx eliminated from the exhaust. Yes, my friend's 2002 7.3 gets better mileage and is just as capable (and he does not need to add DEF). But I'd rather have the 2013.

Thanks for listening, and as always, send questions on clean diesels our way.

Erich
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Old 03-26-2014, 03:51 PM   #17
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Originally Posted by FiveStarDEF View Post
crewstx:


I believe the Cummins in your RAM has active regen similar to the Ford. I also believe it is similar to the Ford in that delayed injection of fuel in the cylinder is used to add heat to the exhaust. This can (in unusual circumstances) result in oil dilution due to washdown in a COLD cylinder.

Chev/GMC Duramax may have come up with a better approach: they added a 9th fuel injector after the turbocharger to add fuel and create heat. Of course it another part that can fail...


Erich
Cummins also uses a 7th injector in the exhaust. Ford is the only one to fire a fuel pulse during the exhaust stroke. Im on the fence on what is better. I have seen more than expected failures in the exhaust mounted injector from carbon build up. The International 6.4L that Ford used in the Superduty had a significant oil grow syndrome from regen but the 6.7L Ford designed engine does not seem to have any oil grow affects from firing during the exhaust stroke like the 6.4L did.
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Old 03-26-2014, 06:07 PM   #18
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jamesrxx951:

Thanks for correcting my error on how the RAM Cummins adds heat during a regen cycle, I'll add the information to our library, and look for additional information on how the RAM Cummins works. The information I has was from a Cummins report on engines that are used in vehicles other than RAMs. I assumed that the same solution would be used on all their engines. Most of the information we have is on the 6.7 Ford system that we own.

Regarding late fuel injection on the 6.7 Ford: I'm on my second oil change (do them myself) and have not found any dilution at all. Since I had never owned a diesel until June 2013, all my previous oil changes (over 100 in the last 20 years) have been on gas engines, mostly MOPARs (slant sixes and V8s up to the 2 X 440s in our boat) and Chev 6s and V8s. I was surprised at how black the used oil is in the diesel vs. the oil from my gas engines. I understand this is normal.

I've found DPF designs that use electrical heaters to oxidize the particulate matter in my research. They are intended (I believe) for installations that have access to higher voltage than 12 or 24 VDC (like a large genset). This seems like a good idea on the surface, but energy is energy, and that is what makes burning fuel in the exhaust a reasonable approach.

Thanks again for adding to our knowledge!

Erich
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Old 03-26-2014, 06:52 PM   #19
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Originally Posted by FiveStarDEF View Post
jamesrxx951:

Thanks for correcting my error on how the RAM Cummins adds heat during a regen cycle, I'll add the information to our library, and look for additional information on how the RAM Cummins works. The information I has was from a Cummins report on engines that are used in vehicles other than RAMs. I assumed that the same solution would be used on all their engines. Most of the information we have is on the 6.7 Ford system that we own.

Regarding late fuel injection on the 6.7 Ford: I'm on my second oil change (do them myself) and have not found any dilution at all. Since I had never owned a diesel until June 2013, all my previous oil changes (over 100 in the last 20 years) have been on gas engines, mostly MOPARs (slant sixes and V8s up to the 2 X 440s in our boat) and Chev 6s and V8s. I was surprised at how black the used oil is in the diesel vs. the oil from my gas engines. I understand this is normal.

I've found DPF designs that use electrical heaters to oxidize the particulate matter in my research. They are intended (I believe) for installations that have access to higher voltage than 12 or 24 VDC (like a large genset). This seems like a good idea on the surface, but energy is energy, and that is what makes burning fuel in the exhaust a reasonable approach.

Thanks again for adding to our knowledge!

Erich
Electric heating would require a lot of energy to create the high temps for DPF cleaning. I did not know there was systems like that in place other than for DPF cleaning at a dealer. Those Kilns they use are high amp and high voltage.

I found a few sources of the 7th injector so im pretty sure Ford is the only one that does not use a dedicated exhaust injector.

Cummins Engine Maintenance, Service and Repair in FL, GA and TN

6.7L Cummins Emissions System Overview
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