Saving diesel fuel

[sailer]

I hear lots of people want to put a 6" or 7" pipe under there monte but if you do that you are restricking a lot of air going under the unit ,, it only has about 16" at the most and keystone says on the new cap of 06 most air goes under the unit to lift it so its lite on the road,,. well guess what , if you block off 7" of air you are now down to 11" or less of air so you are now restricting about 40% of the air or ,, its a drag behind you,, those tubes belong in the unit or on the back but thats no good either as now you make a drag of air caught on the back so more diesel to pull it down the rd ..
i think you have to think of these items as some like to carry ladders etc under the unit , thats ok in the camp grd but not on the rd john

[dsprik]

Interesting point, John...

[ole dude]

Can you put those air deflection thingys underneath?





naaahhh

[HamRad]

Sailer,

I am not knowledgeable about air flow but it seems to me that you would have to be traveling very fast to get enough "lift" from air around the trailer. The "explanation" from the Keystone folks sounds strange to me. Maybe if one had the "chrome plated slotted tailgate" then enough air would be directed under the trailer to make it fly!

It is an interesting thought but I suspect adding the carrying tubes has little effect on the air flow.

HamRad

[Pete Hanson]

I have to believe that the air turbulance created by the TV does a lot more harm to mpg than a little tube mounted under the Monty. Expecting enough lift from airflow under the 10,000+ lb. rig to "lighten the load" sounds like a lot of sales talk to me more than reality. It would be interesting to see the aerodynamics model that Keystone would use to back that up.

[skypilot]

The most aerodynamic thing would be to put an air dam that just barely clears the ground. Air going under the unit still has to hit the axles and the other stuff hanging out down there. Think of race cars and high end sports cars -- the air dams used up front and around the wheel fairings are for more than good looks, they keep that air from getting under there and increasing drag. (or so I was taught in my early years just after the horseless carriage came into being )

[dieselguy]

I'm with skypilot ... a rug tube under the belly probably doesn't do any more for resistance than the axle tubes. A fiver is like traveling with 2 4X8 sheets of plywood standing straight up on top of your bed rails ... not too aerodynamic. I've read where the wind traveling around the back of your unit actually creats a tremendous amount of drag depending on the design of your end caps. If you're trying to reduce wind resistance, I'd be looking into any devices that smooth out your draft.

[bigmurf]

What about the spare tire then?g

[Ozz]

I think we should turn this dilemma over to the 'Mythbuster' guys, remember, the tailgate down, versus up, was proved to be a non-factor.

[skypilot]

On another thread we had some members who had added some type of vortex generators on their rigs. I showed that to my 'big boss' and he put some on his 5er late last week. He is currently on a trip to OK and TX this and next week. Hopefully he is keeping track of mileage and we'll see if they did him any good. Definitely not scientific but practical I guess.

These things (plastic and they go on the trailing edges of your unit) are designed to disturb the air and cause it to fill in behind your trailer more uniformly -- reduces drag and all. I know how and why they work on aircraft; can't imagine us going fast enough to get much effect on vehicles but never know till we see actual results ..

[richfaa]

My shinny new Ford has a air dam up front that marketing says directs airflow under the truck thereby improving MPG. I would hate to see what the MPG is without the airdam as it is not all that good with it??

[TLightning]

These things are so heavy and have so much parasite drag, I really don't think anything can help mileage except reducing speed, reducing load, reducing uphill driving, and reducing head wind.

[sailer]

Well the tow rig has a lot to do with it.. if you buy the rite truck for what you are towing its great but if you buy a tow rige that has a very heavy load built in as if you load tooo much fuel at 9.6 lbs per gal its a drag ,,, if you buy a snow plow rig its 1100 lbs to the front end , if you buy a camper pack and don't have a camper , its no good on the mpg so even if the price is great and the truck is free , you will pay in mpg so who are we kidding , it was a good deal, well it belongs up north in some const office to plow snow and take people to the job sit , not pull a monta ,, if you can't get 10.6 or 11.00 pluse all the time its wrong and you will pay for it in mpg and truck payments or trade it john

[richfaa]

Well the Ford is a much heaver truck than the other two and we pay in MPG for that. Diesel fuel weighs @7.15 lbs per US gallon.(it varies a bit depending on blend) The snow plow package does not include the actual snow plow but is bigger springs and beefed up front end. The camper package is the same for the rear suspension. Snow plow package has a 6K front axle rating and the camper package has a 9K rear axle rating on my 08 F-350. Both of those packages add little weight to the all over truck. We are now pulling the 3400 anchor up I-75 from Florida and the on-board PC reads 10.8 and we were in those rolling GA hills yesterday.. We do the Cumberland gap today. We turned 10K miles on the truck yesterday.Allegedly it should pick up a bit on MPG..

[rvfirefighter]

I have been a fulltimer for almost 8 years. I pulled a 2000 Montana 3250RL for 5 years with a 2000 F350 dually diesel truck I bought new. I now have a 2005 3670RL Montana that I pull with the same truck. I have pulled these units over 100.000 miles all over the U.S. including Alaska. I added a 50 gal. tank to the bed of truck 3 years back and fill it whenever I find diesel at a good price. I added air bags to my suspension to assist with the load of fuel.
During all this pulling the only difference that seems to make a difference in fuel mileage is pulling against the wind or elevation changes out west.
I have gotten between 11 and 13 MPG. for all these years. I have over 135,000 miles on my truck.

[bigmurf]

Rich: You just lost me, I-75 crossing the Cumberland Gap ? Grew up there but I can't make it work. I-75 crosses Jellico mountain (by the BIG cross next to the porno store)

[richfaa]

You are correct. I ran old RT 25 many times when in the military ..things stick in your mind.
(you mean the adult store.??. I think it is nice that they have stores for adults so there will not be screaming kids around and you can buy adult games like monopoly and nice gifts for the wife....why they even have videos for adults..no cartoons.But Helen won't let me stop??


Visitors traveling on Interstate 75 in Kentucky should exit on Highway 25E at Corbin. Cumberland Gap is located 50 miles south of Corbin on 25E.

Visitors traveling on Interstate 75 in Tennessee should exit on Highway 63 at Jacksboro/La Follette. Proceed east on Highway 63 to Highway 25E then north on Highway 25E approximately 2 miles to Cumberland Gap National Historical Park.

The big Ford 6.4 Ate Jellico grade for lunch..Helen was driving and she did not even notice..

[Jim Jarvis]

quote:Originally posted by richfaa

You are correct. I ran old RT 25 many times when in the military ..things stick in your mind.
(you mean the adult store.??. I think it is nice that they have stores for adults so there will not be screaming kids around and you can buy adult games like monopoly and nice gifts for the wife....why they even have videos for adults..no cartoons.But Helen won't let me stop??


Visitors traveling on Interstate 75 in Kentucky should exit on Highway 25E at Corbin. Cumberland Gap is located 50 miles south of Corbin on 25E.

Visitors traveling on Interstate 75 in Tennessee should exit on Highway 63 at Jacksboro/La Follette. Proceed east on Highway 63 to Highway 25E then north on Highway 25E approximately 2 miles to Cumberland Gap National Historical Park.

The big Ford 6.4 Ate Jellico grade for lunch..Helen was driving and she did not even notice..

Out of curiosity Rich, now that you have some miles behind you, how do you rate your V10 vs the diesel? Notice any diff pulling the hills?

[richfaa]

Was just talking about that over dinner tonite. We have run this same route with both the 05 V-10 and the 08 6.4L pulling the same 3400. Only difference in the trucks besides the motor was the 08 is a 4X4. There is of course a big difference Example we pulled the Jellico grade effortlessly with both trucks.However with the 6.4L if I was running 55 mph behind a 18 wheeler that was loaded and slowing on the grade with the 6.4L I can pull around him throttle up to 65/70 or faster with no efort.. the Big block gas motor will not do that..the diesel is doing what the diesel does best..To be fair when we throttle up the diesel the boost is running 36/38 and the EGT is 1170/1200. We are back to 55 as soon as we are around the 18 wheeler.The MPG between the two is not all that great..We did 8.8 average today 10.8 yesterday.On the average that is about 2MPG better than the V-10.. Pulling the hills the diesel shines..other than that... little difference...just my experience..

Helen was driving over the jellico grade north bound. I never said a word as she was keeping the speed limit. At one point I did tell her to "mind the EGT"s as she was pushing 1250 Degrees..she backed off a bit and all was well. They are both good motors..For what we are doing now the diesel does a better job.

[sreigle]

2 mpg is not much but 10 is 25 percent better than 8. Back when diesel and gasoline were nearly the same cost per gallon, that would represent a significant cost savings. With diesel now so much more costly per gallon than gasoline (why????) that difference is not so big in $$. My 6.0 diesel got 30 to 40 percent better mileage than my 1999 V10. This Dodge does better than the 6.0 in mileage by quite a bit but still the dollar savings on fuel is nowhere near as big as it used to be.