Need help with thinking thru towing improvements

So the top 4R pic is my old towing setup and I would avg around 14-15mpg at highway speeds etc. Since moving to a tacoma my mpg has been crushed where I get btwn 9.7 -11.5mpg at the same speeds and towing to the same places.

The green line represents what I feel is the cause, the air having a chance to slam into the teardrop vs maybe clear it a bit better. My main reference for this is one morning I headed to the desert at 7 am before any headwind picked up etc.... I was getting in the 12's. I made it half way and biked, then in the afternoon I continued my journey and it dipped into the 9's for the rest of the trip as the wind had started. I NEVER saw it go this low in the 4R. The irony is the tacoma gets considerably better mpg without towing than the 4R did.

So my question, would I regain some MPG with using a bed cap/topper, soft or hard (NOT tonneau)? I am basing this on keeping the wind up higher before it hits the teardrop. Additional thoughts?

 

Comparing one vehicle to another as far a mpg while towing is difficult at best, there are too many variables. (Yes I’m aware of all the similarities between the two vehicles) Anytime you tow no matter how light or heavy the trailer you are going to experience lower mpg. Teardrops are pretty light so I’m surprised you are getting as low of mpg as you are. Out of curiosity how much does your tear drop weigh????
I doubt the problem is due to aerodynamics. Teardrop trailers are actually very aerodynamic. I think putting a shell on your truck won’t improve mpg at all. It may even make it worse due the the added weight.
First thing I notice is your tires. They do not look like what came from the factory. If those are after market tires that are bigger, taller, wider, and/or heavier than stock , that may be your problem right there.
Also how are you determining your mpg? The most accurate way is to fill the tank, drive, fill the tank again and divide the miles into the number of gallons it took. I may be wrong but it doesn’t sound like that’s what you are doing.
Anyway there are lots of possible reasons for your poor mpg but I doubt it is due to wind resistance and I doubt a camper shell will improve your mpg.

 

Adding a soft toneau is going to be the best bet for not adding weight but improving fuel mileage. Find one that can roll up tight front if you need to put stuff in the box.

With my setup, I get up to a 20% drop in fuel efficiency when towing loaded for camping.

 

I would go ahead and add some air bags with some Daystar cradles. This will at least get your truck riding level and and still give you full articulation of your suspension.

Not quite sure why your MPGs are that low either. I have a pretty large slide in camper that acts like a wall in a head wind. At worst I was getting about 10mpg and best I'm around 15mpg. One thing that helped were the tires I went with. Since I needed E-rated, I chose to go a little skinner which shaved about 6-7lbs per tire compared to my SL while keeping the same height. It may have only given me an extra mile or two but it helps.

 

^^
Interesting facts observed:

Non-OEM Tires (the ones that came with) that can weigh down the vehicle/also affect gearing?
Factoring MPG based (the manual way) on total miles traveled divided by gallons.

 

Other than a 3rd gen Tacoma being physically able to pull a trailer. I doubt if Toyota invested any amount of time or resources into the truck bring able to tow, or tow anything well. Toyota certainly didn't take any time looking at MPGs while towing. How many times do you see a thread complaining about shift points and low end torque. The overwhelming response to that is always the 3.5 was designed to improve gas mileage. Not mpgs while loaded or towing a trailer, even a trailer that weighs less than what the Tacoma is capable of towing.

Toyota may have spent more time and resources on how well or efficiently the 2nd and 3rd gen Tundra can tow.

The best improvement for towing is to use a truck that isn't a 3rd gen Tacoma, although they can tow a trailer. They are not the best at doing so. Toyota did not engineer them for it.

 

Have you had an ECU update. This has helped with shifting and MPG is slightly improved.

 

Biggest issue is the stock gearing in the automatic. Swap to 4.88s and it’s gonna be better.

topper might help a little but I’ve never really noticed much if any difference personally

 

and side note, I'm aware of the myth busters episode, not sure how much tha

the teardrop is btwn 1800 - 2000lbs. What would you relate it to if not aero for my scenario on the same day when I was in the 12's in the morning then 9's in the afternoon once the headwind started? I was going 70+ mph both times on similar terrain in the same vehicle. As for calculating.... I'm just going off the dash. oh and as for tires, no they aren't stock but I had heavy KO2's on the 4R and these are 6ply duratrac's which are def lighter than the BFG.

 

interestingly I also towed with the new Tundra and that was down from 21mpg without towing to 13mpg towing this same trailer

 

no mod to the ECU (yet)

 

ok, yea that's one thing I'm thinking

 

I have to slightly disagree with @Sprig regarding the aerodynamics of a TD. The rear of a TD is about as aero as you could hope for. The front of a TD is not at all. In an ideal world you would have a nice smooth transition between the tow vehicle and trailer... think semi trucks and what they do to minimize the gap between the cab and trailer. You want the shortest tongue and a TD that closely matches in size/shape with the tow vehicle punching the hole through the air. The teardrop shape in and of itself would be aerodynamically awesome if it were not behind a tow vehicle.

@RevelTaco I think you're on the right track regarding the difference in height between the Tacoma and TD. Adding a canopy, even something like a soft topper, would very likely improve your mileage in this case as it would help cut down on the size of the gap between your truck and TD. I don't think that a tonneau would do much to help. Other things that help: Nothing on the roof. Nothing on the sides. People love bolting stuff onto the top and sides of their trucks and trailers. It's no big deal when you're putzing along a forest road but it becomes hugely inefficient at highway speeds. To put it into perspective, the side rearview mirrors on vehicles are estimated to contribute to between 2% and 7% of the total aerodynamic drag of a vehicle.

I know from experience that on the highway I take a bigger MPG hit from having a canoe on my truck than I do from hitching up my TD.

 

Yea I had the spare mounted on the top of the TD…. Thought taking it down would help but it didn’t so I feel
That it means the air is just slamming into the front. I want some type of bed cover anyway and I think a soft topper is my best option as regardless the bikes will be locked as I know a thief can break into whatever they want and I like the use of the bed a good bit.

 

Even without the trailer in tow head winds grossly effect mpg. It’s expected your mpg will decrease if you’re bucking headwinds. Driving against head winds is like continually driving up a grade or hill. Look at your truck itself, not exactly aerodynamic. It’s far less aerodynamic than your trailer.
Again you can’t really compare the difference in mpg between the 4R and Taco, there are too many variables, too many differences, too many unknowns.
The way you are figuring mpg is not really inaccurate.
I still think the tires are a factor in your poor mpg. Besides weight , size and height are important factors.
But hey, if you want to spend a couple thousand on a camper shell, go ahead on. If it improves your mpg (which I doubt) it would be slight. It would probably take 10 years to reach the break even point

 

Yea I’ve definitely been running the numbers and even with just using the dash values, it’s like $35 extra for most trips so not bad. But how could it be the tires if when I’m not towing I still get 21mpg going 75-80mph? I wouldn’t get the topper JUST for the mpg, I want something to cover the bed for storage options. And yea the headwind makes sense, which is why I further feel the wind slamming into the TD is causing an issue

 

Note, installing a hard topper will add considerable dead weight. I don't know what a soft topper weighs but it should have aerodynamics when towing your camper.

 

I haven’t seen a need for bags (yet) as it only lowers it 1” in the rear. I did have bags on the 4R but that was because my prior TD had a much heavier tongue weight

 

Got it, think it was the way it looked from the picture and the green line.

 

I tow a 3500lb boat and trailer. The boat except the windshield is quite aerodynamic. When I tow my boat my mpg drops to 9 to 11 mpg depending on various factors. If I’m fighting a headwind it gets obviously worse. If I’m driving on long grades or in the mountains it’s even worse. 70 mph and above it gets worse yet.
Wouldn’t hurt to try an ecu tune, different tires may help, driving slower my help. Figuring your mpg based on miles driven and actual gallons used may provide a more accurate mpg.
Bottom line I think your mpg while towing or not towing is just what it is. I really don’t think anything you do is going to make a real cost effective difference. Just enjoy your truck and teardrop as it is. I stopped figuring my mpg while towing. I figure it is what it is, don’t really want to know any longer. I just concentrate on having fun with the truck and boat. Good luck, enjoy the hell out of your teardrop.