Trailer Mystery

[turnbaugh]

I am still on a quest for the best tow vehicle and could use some other brains to figure this out.

I have a friend with a 2013 Dodge Ram 2500 diesel. He has a 28' trailer with a flat front. he hauls a SR, tools, tires and a golf cart.

I rented a 2013 Dodge Ram 2500 diesel. I have a 20' v nose trailer. I haul a SR, wheels, tools, tires and NO golf cart.

He gets 14 mpg. I get 9.8. Both driving highway at 65ish.

Both trailers are level on the hitch. Both are TAG.

What the heck? Any explanations?

[Matt King]

That seems low, but there are lots of variables, like wind, hills, problems with the specific truck, etc. One towing data point is hard to make a judgment on.

[racerdad2]

Your friend's truck may be 'chipped' I re-programmed my Ford. Set it on first level - tow. Better power. Better mpg by 15-20 %.

[ewcmr2]

How many miles on each truck? The Cummins take a long time to break in....

[tim gaffney]

I have a barely used 32' trailer for $8k. It has a about 10k miles. Has been sitting for 3 years now

Tim
248 802 6755

[Laird]

I recently rented (thru Enterprise) a similar Ram 2500 Cummings and towed a moderately loaded 24' (with 9' high box….extra draggy) and got 14 mpg over 2000 miles or so. That was nice compared to my old F250 V10 @ 9gph. The extra cost for DEF was a bitch at $8/gal though.

[BeerBudgetRacing]

He gets 14 mpg. I get 9.8. Both driving highway at 65ish.

My son has a co-worker that bought a trailer and car 500mi away. Went to get it and on the way home with it had 3 flat tires and couldn't get above 50mph.....

Axle bearings were shot. He was dragging a sled.....

How are your bearings?

[Daryl DeArman]

I have a friend with a 2013 Dodge Ram 2500 diesel. He has a 28' trailer with a flat front. he hauls a SR, tools, tires and a golf cart.

I rented a 2013 Dodge Ram 2500 diesel. I have a 20' v nose trailer. I haul a SR, wheels, tools, tires and NO golf cart.

He gets 14 mpg. I get 9.8. Both driving highway at 65ish.

Both trailers are level on the hitch. Both are TAG.

What the heck? Any explanations?

Yeah, one of you is better with a calculator than the other.

Things that could make a huge cumulative difference (but not 50% huge):

Axle ratios on truck.

One towing in OD, One not.

If it was a relatively short trip how you accelerated up the on ramp can suck a ton of fuel that takes awhile to bring that average back up.

Inflation and alignment on truck and trailer tires.

2WD v. 4WD.

Brakes slightly dragging on one trailer and not the other.

[turnbaugh]

Thanks for alll the comments and ideas. More data based on the questions.

Dont know the axle ratios but a good point and will check.

Both trips we used for comparison were all highway and were both over 800 miles.

The high mileage trailer is brand new and the low mileage trailer was just overhauled with all bearings and brakes checked

Would the axle ratios make a 40% difference?

[racerdad2]

What were the rpms at 65 mph on each truck ? If one has 4:10- 1 rear gear ratio for heavy towing & the other has something like 3:10 - 1 for economy, that's a big difference in cruising rpm. My 7.3 pulls well at 65 mph - 2200 rpm with 3:73 - 1 rear. If she were geared at 65 mph - 3000 rpm she'd run through the fuel pretty fast.

[Brian]

I believe the 2013 Ram 2500 with diesel only came with the 3.42 diff ratio, no other option was available for the single rear wheel trucks. Dual rear wheel had other options available.

From reading forums the 6.7 liter CTD is known for variable fuel mileage. If I was looking for a new diesel truck I would look at the new Ford. They redesigned the intake/exhaust to put the exhaust into the valley and the intakes on the outside of the heads to improve the flow to the turbo.

Brian

[Snakedriver]

HI Guys,

I bought a 2012 F25 6.7 oil burner. It gets about 18 MPG Hwy and varies with the tow load. I haul a tall flat front enclosed trailer that will pull the mileage down to about 13 or so depending on speed and hills.

I have noticed that load doesnt seem to effect MPG much. Im sure it does. Butf I believe that it is mostly an aerodynamic thing...That flat front is a big ass sail working the wrong way! I have had it go to 11 MPG when I was running around 70+ so I try to cruise around 60.

Those numbers are based on the onboard systems.

That 6.7 really is one helluva an engine.

Leo

[Daryl DeArman]

Would the axle ratios make a 40% difference?

I am not a diesel expert by any means.

My understanding is throttle position and rpm are the two major contributors to fuel consumption.

My RV has a 5.38 rear end. I get about 7MPG. If I was to change to a 3.10 axles, I would be turning 42% less rpms but my foot would be much closer to the floor at all times to push that brick through the air. I'm guessing the net gain wouldn't be much in MPG (maybe 15% at steady state level highway driving) and mileage and performance would be much worse on any hills and accelerating from a stop.

[brownslane]

I am not a diesel expert by any means.

My understanding is throttle position and rpm are the two major contributors to fuel consumption.

My RV has a 5.38 rear end. I get about 7MPG. If I was to change to a 3.10 axles, I would be turning 42% less rpms but my foot would be much closer to the floor at all times to push that brick through the air. I'm guessing the net gain wouldn't be much in MPG (maybe 15% at steady state level highway driving) and mileage and performance would be much worse on any hills and accelerating from a stop.

Daryl, the result may be the opposite; I changed my rear end ratio on my old truck from 3:23 to 3:73 and GAINED a full 5mpg when towing. The reason is that the truck was running with 30% less throttle at the same speed. As well, there was less friction internally as the truck ran cooler. Go figure! With the 3:23 my foot was buried, just on the edge of kicking down the transmission. Really beat the engine...with the higher revs the engine ran with much less effort.

[Daryl DeArman]

Daryl, the result may be the opposite; I changed my rear end ratio on my old truck from 3:23 to 3:73 and GAINED a full 5mpg when towing. The reason is that the truck was running with 30% less throttle at the same speed..

That's what I was trying to say....combination of throttle and rpms. Going with a taller gear that requires more throttle offsets any gains that the lower rpm got you. Going with a lower gear that causes more rpms without any appreciable reduction in throttle position isn't doing you any favors either.

[racerdad2]

The key with diesels is to find the sweet spot in rpm & throttle. I dropped mine from 4:10 to 3:76 and keep her at 60. The flat front end really catches the air. Running in the rain, you can see the airflow pushing out about 6' on either side. I'm fabbing a V-nose for her this winter. Will be interesting to see if she tows better & gives me a boost in mpg. She runs 12k #'s or better fully loaded. 33' is a bit much for a tag along....

[ewcmr2]

That 6.7 really is one helluva an engine.

I think that is yet to be proven... On the power stroke forums in the "high mileage" threads there are people posting with <50k! Very few seem to be over 100k. I'm guessing the power stroke fans are loving the 6.7 as compared to the 6.4. When there are more over 250k than under 100 we can really start to know id the 6.7 is a good engine.

Back on track with the Cummins thread, the old 12 valve engines get the best mileage. The newer they are the more power they make and the more fuel they burn.

[Snakedriver]

I agree...The longevity of the 6.7 remains to be seen. I have only 30K on my machine, but boy does it run. Im not a fan of all the automation in the engine, but It while its working, its working.

I hope they last. Im plaining on keeping the truck for at least 15 years or so.

Leo

[Swift17]

I have noticed that load doesnt seem to effect MPG much. .... I have had it go to 11 MPG when I was running around 70+ so I try to cruise around 60.

The key with diesels is to find the sweet spot in rpm & throttle.

So, OK - 2006 GM Crew Cab Duramax/Allison - LLY/403ci/310hp (vs. the mid year release/update LBZ/406ci/360hp - bought on "close out") tow a 20 foot tag and it's 16" on centers floor and semi rounded nose, with built-in mica cabinets/FF/Tools/EzGo/the world's heaviest scale platforms [ugh! circa 1986] and steel [ugh! again] 10 x 20 ez-up canopy).

After 140k miles, Jason's then college roommate worked at SuperChips and put a "tow tune" on the chip at their facility and post install tested

Now @ 180K truck only ...............- 22/24 mpg @ 64-68 - 70-73 down to 19/20 mpg
................. truck @ full trailer.....- 12/13 mpg @ 64-68 - 70-73 down to a solid 10 mpg

truck/trailer with all [and I mean all] racing "stuff" removed and filled with just and much lighter dresser, headboard, end tables, mirrors, mattress, small couch, four kitchen chairs & table - [daughter post grad school apt. to apt. move - Gainesville to Tampa -virtually all flat roads] NO CHANGE in mileage - driving up and then home empty, negligible change in mileage !!!

As to nose modification read a few years ago [SAE paper ?] that a "v" nose is nowhere as efficient as a "round" noses as evidenced by the "bubble front" on commercial carrier trailers and sculpted cab tops Kenworth/Peterbuilt trucks -

I wonder if a p/u bed cover vs. bed cap (which I know would help) could significantly help

[Snakedriver]

This spring I put a cap on my F250. I towed a TR4 down to FLA and noticed maybe a 1 or 2 MPH increase, but that may have been due to a number of factors.

Round vs pointy is a proven aerodynamic thing. Round is better than pointy. But I would think that pointy is cheaper than round, and better than flat.

I was also thinking outside the box...Imagine something like a big neoprene sock that would connect the rear of the truck (with cap) to the front of my flat nose trailer...That would be the best! but I think Ill just wait till I can afford a new trailer!

Leo

[Brian]

I had a vee nose on my last trailer, and got about exactly the same mileage as I would have with a flat nose, I think. I added Airtabs and picked up a decent increase, between 10 and 15%. It also reduced sway a lot. That vee nose swayed worse than any trailer I ever had. If a truck was passing you the vee nose funneled air between the trailers, created a venturi effect and the suck was amazing. Running alone the air would tumble from side to side off the point of the vee and create sway. The only thing that cured it was putting a truck camper on the truck to completely mask the front of the trailer.

Brian

[racerdad2]

I've been considering the Airtabs. Good to hear they work so well. Scratch the V nose. Add Airtabs. Add rear spoiler to back of truck topper to deflect air over the top of trailer. Ponder the round front for the trailer.... Impressed with the Chevy's mpg ! Aero drag increases dramatically above 60 mph. At 80 mph I can watch the fuel gauge drop to empty minute by minute

[Swift17]

http://www.youtube.com/watch?v=bfTv8Nt-x6o

................no warranty, expressed or implied

nor the speed of the "second" fan (cynic that I am)

[Modo]

round or streamline the back would be the best like a Honda Insight I would think, but would have to put the lights hanging out on a piece of aerotube at the extreme rear........... extra length may have to be storage only .... tuff one it is!!!! ..... how bout run the car only with minimum repair and a second trailer for long tows, open or low n streamlined, button push clamshell would be nifty, tires n tools in toiw truck, quick compete and out, saw a nice Reynard Atlantic on a open trailer at the Glen last year although trailer had tire storage hitting the air in front!!!

[brownslane]

Brian is right on point regarding Airtabs. I have them on my van, the 34 foot trailer and the motor home. 10% increase in mileage in the MH without towing. The van with the trailer is 11% better and NO SWAY at all. Remember this is a 34 foot TAG! Really nice.

And in the rain, when you cannot see down the sides of the van due to swirling air, you can now see straight down the sides. Very little turbulence behing the van at all.

In the snow, when the van (without air tabs installed) would blow all the snow off two lanes, with the tabs, it only blows the snow off about a foot on either side of the van. A LOT less turbulence. You know what the back door of the trailer looks like after a run...all covered in dust/dirt? Not with the tabs. Like 80% cleaner; this tells me there is much reduced rear turbulence.

Cheaper and more effective than a chip come to think of it.

Best, T

[Swift17]

Hey Tom .........

Great info in the post - pics of the ATs as installed possible ?

EJ

... and saw a quite a few of these on recent trip Fl/Watkins

http://www.atdynamics.com/trailertail.htm

[Daryl DeArman]

... and saw a quite a few of these on recent trip Fl/Watkins

http://www.atdynamics.com/trailertail.htm

Regarding those trailer tails, OTR drivers are getting about a 6% increase in fuel economy with them. They are a bit over $2K.

The break even is $33,333.33 in fuel cost. No big deal for an OTR driver, he will get his money back in a year or less.

You and me? Going to have to tow 80-100K miles before you save $.01.

[Modo]

trailer tails get tricky, ...... have to go to NACA shape and perfect is bout 6-7 degree falloff for perfection, ouch, why i say u might only put storage in there or, ...... push a button and three sets of tires go up and ramps come out, car too, driver jumps in and and AWAY WE GOOooooo!!!! jes keep the dern truck/tow vehicle under 2K RPM n quit dream'n LOL

[racerdad2]

Nose cone looks promising.... Any first hand experience ?

[Modo]

what the hell i a air tab, pictures or reference to pics above if i missed it ...... until then, smoke n mirrors

[Swift17]

http://www.airtab.com/video.html

Saw a couple trucks with these as well on I-95 BUT more "Newel/Provost" motor-home trailers had them ... Query: If they are so efficient then why doesn't say, Swift Trucking/Martin Brower [McDonald's Distribution]/Wal~Mart use them with the side under-the-trailer curtains that are starting to pop up on alot of OTR trucks ? There are a TON of these style trucks on the road

[DaveW]

http://www.airtab.com/video.html

Saw a couple trucks with these as well on I-95 BUT more "Newel/Provost" motor-home trailers had them ... Query: If they are so efficient then why doesn't say, Swift Trucking/Martin Brower [McDonald's Distribution]/Wal~Mart use them with the side under-the-trailer curtains that are starting to pop up on alot of OTR trucks ? There are a TON of these style trucks on the road

That is the question I have - I don't have a sway problem that is severe enough to worry about (1974 G30 Chevy Van and 1989 22' tag trailer with nose cone), so mileage improvement would be my reason to use them. With the varying small mileage improvement results I have seen, it doesn't seem to me to be worth the $200+ to do it.

[brownslane]

That is the question I have - I don't have a sway problem that is severe enough to worry about (1974 G30 Chevy Van and 1989 22' tag trailer with nose cone), so mileage improvement would be my reason to use them. With the varying small mileage improvement results I have seen, it doesn't seem to me to be worth the $200+ to do it.

Dave, I tow about 10,000 miles a year. With fuel costs almost $6 a gallon up here for the cheap stuff, I paid it back in the first year. On the 34 footer the tabs reduced the rear sway in cross-winds to almost nothing. As well, the "suck and blow" when passing or being passed by transports almost disappeared. I can tow with two fingers....instead of clutching the wheel! I got them not to save coin but to make the rig safer. Works a charm!

Even if it cost me 5% I would still use them.


Sorry for the thread drift here guys, but if I had to choose between air tabs and that stupid $500 Bully Dog, I would opt for the air tabs, hands down. Install with self-adhesive strips already applied to the tabs. Comes with a template to determine placement. Peel and stick takes half an hour to do your tow vehicle or trailer. Be sure and do the ROOF of the truck or trailer; it makes a difference!



My tabs are in their 6th year and not one has fallen off.

Tom