Reply
 
Thread Tools Search this Thread Display Modes
 
Old 12-16-2012, 10:13 AM   #29
Rivet Master
 
dkottum's Avatar
 
2012 25' Flying Cloud
Battle Lake , Minnesota
Join Date: Jun 2009
Posts: 7,716
When towing the Airstream, another thing that uses more fuel is the auto transmission shifting down on small, short grades on the roadway.

With our new Dodge Hemi I found keeping a speed that allows RPM above 2100 puts the engine in its higher torque range and it does not shift up and down. At 55-60 mph that means running in a lower gear, which is fine with me. Because it still uses less fuel at a constant rpm than shifting up and down for grades.

This is still dependent on wind conditions and direction.

And of course less wear on the transmission and engine.

doug k
__________________

__________________
dkottum is offline   Reply With Quote
Old 12-16-2012, 11:57 AM   #30
Rivet Master
 
2005 19' Safari
GLENDALE , AZ
Join Date: Aug 2004
Posts: 2,441
Besides reduced drag, I think driving a little slower than traffic reduces the number of vehicles that you need to pass. Keeping up with the pack leads to frequent acceleration and deceleration from cruise control settings, which consumes extra fuel.
__________________

__________________
Phoenix is offline   Reply With Quote
Old 12-16-2012, 12:53 PM   #31
Rivet Master
 
dznf0g's Avatar

 
2007 30' Classic
Oswego , Illinois
Join Date: Jul 2010
Posts: 9,409
Images: 5
Quote:
Originally Posted by SteveH View Post
I've tried driving 55 with my Duramax, and it doesn't seem to help any at all. I believe this to be because the Allison transmission coupled to the 3.73:1 rear end ratio will not go into sixth gear until about 62 MPH while in tow/haul mode.

Some of my friends say they don't drive in tow/haul, and get a little better mileage, but it's my thought that the whole truck performs better and it is easier on the transmission in tow/haul while towing the 31 footer. Otherwise, why would the engineers do it this way?

It would be nice to have a factory person chime in on this issue.
Diesel and Allison (in particular) is a completely different animal than the gas.
The server is down for its weekly maintenance right now, so I can't pull owner manuals and service info. But, the general rule of thumb is when you are at 75% of the max load for your configuration, TH should be used. Below that figure, using TW doesn't hurt anything. May cause a decrease in mileage...but it is dependent upon terrain, wind, and what you perceive as pleasing.

Obviously this 75% figure is different in every setup. Example a 1/2 ton with max tow and a 30'er will need to be in max tow FOR SURE. a 2500hd Duramax with the same trailer...probably not.
__________________
-Rich-

"If the women don't find you handsome, they should at least find you handy." - Red Green
dznf0g is offline   Reply With Quote
Old 12-16-2012, 02:04 PM   #32
Rivet Master
 
dznf0g's Avatar

 
2007 30' Classic
Oswego , Illinois
Join Date: Jul 2010
Posts: 9,409
Images: 5






Here ya go. This is for a Silverado





Tow/Haul Mode




Pressing this button at the end of the shift lever turns on and off the Tow/Haul Mode.


This indicator light on the instrument panel cluster comes on when the Tow/Haul Mode is on.
Tow/Haul is a feature that assists when pulling a heavy trailer or a large or heavy load. See Tow/Haul Mode for more information.
Tow/Haul is designed to be most effective when the vehicle and trailer combined weight is at least 75 percent of the vehicle's Gross Combined Weight Rating (GCWR). See “Weight of the Trailer” under Trailer Towing . Tow/Haul is most useful under the following driving conditions:
When pulling a heavy trailer or a large or heavy load through rolling terrain.
When pulling a heavy trailer or a large or heavy load in stop-and-go traffic.
When pulling a heavy trailer or a large or heavy load in busy parking lots where improved low speed control of the vehicle is desired.
Operating the vehicle in Tow/Haul when lightly loaded or with no trailer at all will not cause damage. However, there is no benefit to the selection of Tow/Haul when the vehicle is unloaded. Such a selection when unloaded may result in unpleasant engine and transmission driving characteristics and reduced fuel economy. Tow/Haul is recommended only when pulling a heavy trailer or a large or heavy load.
__________________
-Rich-

"If the women don't find you handsome, they should at least find you handy." - Red Green
dznf0g is offline   Reply With Quote
Old 12-16-2012, 05:49 PM   #33
Vintage Kin
 
slowmover's Avatar
 
Fort Worth , Texas
Join Date: Nov 2006
Posts: 7,603
Images: 1
Quote:
Originally Posted by Phoenix View Post
Besides reduced drag, I think driving a little slower than traffic reduces the number of vehicles that you need to pass. Keeping up with the pack leads to frequent acceleration and deceleration from cruise control settings, which consumes extra fuel.
Yes, when FE is analyzed it is vital to not only limit the number and type of acceleration and braking events, but to reduce the steering wheel inputs. It takes energy to change lanes, even when done smoothly. Over the course of 100-miles this can really add up (according to both KENWORTH & CUMMINS).

The ideal is a steady-state speed which needs next to no throttle, brake or steering input. Which may not be as desired (that old teenager programming) as what is required to get from Point A to Point B is different. The balance between time & distance can be altered by the smart driver traveling more slowly, but with adequate safety stops of a predetermined length. Planning those long days by making legs of time/distance is workable.

Alternatively,

Let's say that our TT is one we will tow for 100k in the time we own it. A 20% reduction in fuel burn over that time might be 1,200-gls. At $4/gl that is close to $5k. And if our solo miles are done in like manner the savings may be double or triple that amount.

I found I could improve my solo mpg signficantly by combining errand trips. Fewer cold starts. Few, if any, short trips. After all, most errand trips take us the same places. Second, by doing a better job of driving those remaining miles the savings in fuel underwrites more than 5k of annual vacation miles. With the same fuel budget, "free fuel" for travel.

Fixed income? Ways to maximize that. Fixed length of time available? Ways to maximize enjoyment there. Fuel is just one cost, but it closely tracks wear & tear on my combination rig drivetrain & running gear and thus stands in for more than itself.

More than one way to skin the cat.

.
__________________
1990 35' Silver Streak Sterling; 9k GVWR.
2004 DODGE Cummins 305/555; 6-manual; 9k GVWR.
Hensley Arrow. 9-cpm solo, 15-cpm towing
Sold: Silver Streak Model 3411
slowmover is offline   Reply With Quote
Old 12-16-2012, 07:54 PM   #34
Rivet Master
 
dznf0g's Avatar

 
2007 30' Classic
Oswego , Illinois
Join Date: Jul 2010
Posts: 9,409
Images: 5
And me taking that 1986 Yamaha 125cc scooter along, which gets 94.5 mpg doesn't hurt either for those errands, beach runs, sunset runs.
__________________
-Rich-

"If the women don't find you handsome, they should at least find you handy." - Red Green
dznf0g is offline   Reply With Quote
Old 12-17-2012, 10:04 AM   #35
Rivet Master
 
switz's Avatar

 
2014 31' Classic
2015 23' International
2013 25' FB International
Apache Junction , Arizona
Join Date: Sep 2012
Posts: 4,799
Images: 8
A rule of thumb from the Gas Embargo days of 1973 was a 10% reduction in fuel economy for each 5 mph increment over 55 mph. Thus at 65 mph, one could expect at least a 20% increase in the fuel burn. This statement reflects a still air environment. As Andy stated, headwinds will decrease MPG and tailwinds will increase mpg if the indicated speed is held constant.

The reason fuel savings did not materialize initially for the big trucks was the higher gears were setup for 70+ mph on the interstates. When the newer trucks came along with gears optimized for 55, then the fuel economy numbers improved.

My initial tow from the dealership in Los Angles to Phoenix at 55 mph generated a 17 mpg diesel fuel use and the engine was running at 1650 rpm on the level, right at the leading edge of the high torque band.
__________________
switz is offline   Reply With Quote
Old 12-17-2012, 10:53 AM   #36
Rivet Master
 
1988 25' Excella
1987 32' Excella
Knoxville , Tennessee
Join Date: Oct 2010
Posts: 2,165
Blog Entries: 1
"My initial tow from the dealership in Los Angles to Phoenix at 55 mph generated a 17 mpg diesel fuel use and the engine was running at 1650 rpm on the level, right at the leading edge of the high torque band. "

What model truck?

thanks
__________________
Bill M. is offline   Reply With Quote
Old 12-17-2012, 11:39 AM   #37
Rivet Master
 
switz's Avatar

 
2014 31' Classic
2015 23' International
2013 25' FB International
Apache Junction , Arizona
Join Date: Sep 2012
Posts: 4,799
Images: 8
My TV is a 2007 Mercedes ML 320 CDI diesel. The engine is 3 liters with a 7 speed automatic and air suspension. It gets 27.5 hwy and 22.5 city.
__________________
WBCCI Life Member 5123, AIR 70341, 4CU, WD9EMC

TV - 2012 Dodge 2500 4x4 Cummins HO, automatic, Centramatics, Kelderman level ride airbag suspension, bed shell

2014 31' Classic model 30 twin beds, 50 amp service, 900 watt solar system, Centramatics, Dill TPMS, disc brakes, 16" tires & wheels
switz is offline   Reply With Quote
Old 12-18-2012, 06:34 AM   #38
Vintage Kin
 
slowmover's Avatar
 
Fort Worth , Texas
Join Date: Nov 2006
Posts: 7,603
Images: 1
17 is my goal for the next trailer. We'll see . . . .
__________________
1990 35' Silver Streak Sterling; 9k GVWR.
2004 DODGE Cummins 305/555; 6-manual; 9k GVWR.
Hensley Arrow. 9-cpm solo, 15-cpm towing
Sold: Silver Streak Model 3411
slowmover is offline   Reply With Quote
Old 12-18-2012, 09:35 AM   #39
Rivet Master
 
Lumatic's Avatar

 
1971 25' Tradewind
1993 34' Excella
Currently Looking...
Estancia , New Mexico
Join Date: Feb 2005
Posts: 6,642
Images: 16
Blog Entries: 1
Quote:
Originally Posted by Inland RV Center, In View Post
A great addition to a tow vehicle, is an "Air speed indicator".


Andy
I agree the biggest fuel economy factor seems to be wind resistance. Followed by terrain features such as uphill tows.

An alternative is a manifold vacuum gauge. Tells you how much fuel you are sucking. A wind speed gauge (never used one) would not give you much useful information in situations like towing uphill. There are also mpg gauges but they cost more.

Just wondering. Has anybody played around with using an air deflector on the tow vehicle. The kind that mounts on the TV roof? How about building some kind of deflector similar to those now used on most tractor trailer combinations? Since Airstreams are somewhat aerodynamic anyway would it make a big enough difference to justify this addition?
__________________
Sail on silver girl. Sail on by. Your time has come to shine.
Lumatic is offline   Reply With Quote
Old 12-18-2012, 09:52 AM   #40
CLOUDSPLITTER "Tahawas"
 
ROBERT CROSS's Avatar

 
2003 25' Classic
Zanadude Nebula , WNY
Join Date: Jun 2007
Posts: 11,153
Images: 1
"Just wondering. Has anybody played around with using an air deflector on the tow vehicle. The kind that mounts on the TV roof? How about building some kind of deflector similar to those now used on most tractor trailer combinations? Since Airstreams are somewhat aerodynamic anyway would it make a big enough difference to justify this addition?"

Yep.....

but it didn't add anything, then again....it didn't subtract either.

Bob
__________________
ROBERT CROSS is offline   Reply With Quote
Old 12-18-2012, 10:00 AM   #41
Rivet Master
 
Lumatic's Avatar

 
1971 25' Tradewind
1993 34' Excella
Currently Looking...
Estancia , New Mexico
Join Date: Feb 2005
Posts: 6,642
Images: 16
Blog Entries: 1
Quote:
Originally Posted by ROBERT CROSS View Post
Yep.

Bob
I've wondered the same about camper shells. From what I have read they either don't make any difference or cause lower mpgs.
__________________
Sail on silver girl. Sail on by. Your time has come to shine.
Lumatic is offline   Reply With Quote
Old 12-18-2012, 01:21 PM   #42
CLOUDSPLITTER "Tahawas"
 
ROBERT CROSS's Avatar

 
2003 25' Classic
Zanadude Nebula , WNY
Join Date: Jun 2007
Posts: 11,153
Images: 1
Quote:
Originally Posted by Lumatic View Post
I've wondered the same about camper shells. From what I have read they either don't make any difference or cause lower mpgs.

I can see where a properly designed cap could actually improve mpg.


Bob
Attached Thumbnails
Click image for larger version

Name:	truck-bed-cap-470-0608.jpg
Views:	64
Size:	26.1 KB
ID:	174868  
__________________

__________________
ROBERT CROSS is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



Virginia Campgrounds

Reviews provided by




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 01:53 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.

Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.