Enclosed trailer fuel efficiency

Tech questions that don't fit above forums

Moderator: Team

Post Reply
Wiz_kid53
Member
Member
Posts: 70
Joined: Mon Nov 09, 2015 2:02 pm
Location:

Enclosed trailer fuel efficiency

Post by Wiz_kid53 »

I recently fell down a rabbit hole of trying to come up with something that would improve fuel economy while pulling an enclosed trailer and be collapsible, similar to the trailer tail seen some long-distance truck trailers, but with less open area to minimize drag as completely as possible.

Mostly I’m just curious what you guys would do to try and make your trailer have as little drag as possible? I’m also curious how far it could extend off the back before causing an issue with law enforcement kind of like when you have something hanging out the bed of your truck. Maybe you could add an additional brake light at the end? Let me hear your thoughts!
ijames
Expert
Expert
Posts: 849
Joined: Fri Jul 04, 2008 3:44 pm
Location: Laurel, MD

Re: Enclosed trailer fuel efficiency

Post by ijames »

I have learned a lot about improving fuel economy at https://ecomodder.com/forum/ . They have forums ranging from aerodynamics to driving techniques to lots of other stuff. One of the most prolific and helpful posters in the aerodynamics forum (https://ecomodder.com/forum/aerodynamics.html) is "aerohead". He is mostly self taught, widely read, and has a Tacoma pickup that gets at least 44 mpg. Could be more but I haven't been keeping up there for a while. Several years ago someone there posted about a GM patent from the 80's on partial tonneau covers for improved mileage so I cobbled up a plywood sheet cover going from mid-bed back to the tailgate on my 2005 duramax 2500hd extended cab short bed pickup and got 1-1.5 mpg improvement from 60 to 80 mph. I know there has been lots of discussion about optimizing the shape of the rear on semi-trailers and about the commercial add-ons like you asked about. Besides improving the rear, if you can round off where the sides meet the roof with a radius of maybe 4" (from hazy memory, might need to be 6 or 8") that also helps significantly.
Carl Ijames, chemist not engine builder
carl ddott ijames aatt verizon ddott net
miniv8
Expert
Expert
Posts: 895
Joined: Mon Sep 11, 2006 5:22 pm
Location: ICELAND

Re: Enclosed trailer fuel efficiency

Post by miniv8 »

I've been thinking about closing off the underside of our trailer with plastic sheeting. We got a V-nose already.
The bottom is all transverse beams, and from what I've read about the impact roof bars have on mpg, I'm almost surprised I cant find any information on mpg testimonials of such a modification.
Magnús Aðalvíkingur Finnbjörnsson
User avatar
BOOT
Guru
Guru
Posts: 2895
Joined: Fri Apr 09, 2010 6:23 pm
Location: Michigan

Re: Enclosed trailer fuel efficiency

Post by BOOT »

Back when I read many of those ecomodder post to better understand aero. The biggest problem some posted is most things diy that help aero often barely or don't offset the weight gain.

Now if your are pulling a heavy load already like a semi trailer for long distance then.... IDK what end of the spectrum your trailer would be on, just my 2 cents.
Channel About My diy Projects & Reviews https://www.youtube.com/c/BOOTdiy

I know as much as I can learn and try to keep an open mind to anything!

If I didn't overthink stuff I wouldn't be on speedtalk!
miniv8
Expert
Expert
Posts: 895
Joined: Mon Sep 11, 2006 5:22 pm
Location: ICELAND

Re: Enclosed trailer fuel efficiency

Post by miniv8 »

The aero kicks in at steady state commuting, I think the added weight is just along for the ride after the acceleration is done.

The aero drag goes up at the square of speed, but the weight will just increase time and distance it takes to attain that speed... if I got it correctly.

The brilliance of reducing aerodynamic drag, is the reserve horsepower. If your 400hp truck uses 150hp to maintain given speed with the trailer attached, it will have 250hp reserved for hills and passing.
Magnús Aðalvíkingur Finnbjörnsson
User avatar
BOOT
Guru
Guru
Posts: 2895
Joined: Fri Apr 09, 2010 6:23 pm
Location: Michigan

Re: Enclosed trailer fuel efficiency

Post by BOOT »

miniv8 wrote: Fri Apr 23, 2021 2:00 pm The aero kicks in at steady state commuting, I think the added weight is just along for the ride after the acceleration is done.
Yup most were commuting to work, so unless it's for mostly long trips and not more often just short trips.
Channel About My diy Projects & Reviews https://www.youtube.com/c/BOOTdiy

I know as much as I can learn and try to keep an open mind to anything!

If I didn't overthink stuff I wouldn't be on speedtalk!
JoePorting
Guru
Guru
Posts: 2997
Joined: Mon Jun 14, 2010 3:16 pm
Location: Lake Elizabeth, CA

Re: Enclosed trailer fuel efficiency

Post by JoePorting »

I've experimented with different configurations on my 2001 Silverado pickup and found the best solution for max fuel economy is a full shell. The worse is an open bed with the tail gate down. The second worse is an open bed with the tail gate up. A Tonneau cover is next best, but the best is a full shell. My thinking is that a pickup with an open bed has two low pressure areas that restrict aerodynamics, the cab and the rear tail gate area. When the tail gate is down, this increases the low pressure area behind the cab with the sides of the bed restricting air from coming in from the sides. I think the full shell works best because there is just one low pressure zone behind the truck and air from all four sides can fill the low pressure zone easily allowing the best aerodynamics of the four configurations, and I found around a 4 mpg difference between the best and worse configuration. Just my opinion.
Joe Facciano
hoodeng
HotPass
HotPass
Posts: 1092
Joined: Sat Mar 04, 2017 6:53 pm
Location: South Australia

Re: Enclosed trailer fuel efficiency

Post by hoodeng »

Years ago i remember seeing a 'Myth Busters' episode on the aero of a pickup with different configurations being tested.
What you think works as usual needs rethinking.

One thing i do remember from trailer dragging/ repair truck, don't fill the nooks and crannies with things you 'might' need, have a check list of what actually needs to be in there, make sure it is in there before you leave, and make sure it is full [fluids and gasses] or enough in to do two events. Weigh the trailer at some point on the way to a track, it is usually a boat anchor.
Under the drivers seat, toilet paper, towel, sharp knife and fork, jacket , socks and jocks, fire extinguisher, jumper leads, water, wiper blades, lighter.

Cheers.
Post Reply