10 mpg. Unacceptable
 

Hey there! Well I have a 14'x7' cargo trailer that I converted into a camper. It weighs around 2000#.I pull it with a chevy traverse and get around 10 mpg. I put vortex generators on to see if that would help (no improvement in gas mileage but they made it more stable) now I put a boat tail on it to see if that would help. Thankfully someone is going to put a picture up(I don't know how). So I'd appreciate any comments, concerns or criticism.

I didn't try it out yet.

Thank you

From what I can tell about vortex generators is they are used to fine tune the air flow on a good design.
Vortex generators by nature actually increase drag.
It requires perfect placement to get them to reduce overall drag.

The comment concerning my criticism would be "Posts: 3" You're not there yet, post moar.

http://ecomodder.com/forum/showthrea...ave-35116.html

http://ecomodder.com/forum/showthrea...ack-22075.html

http://ecomodder.com/forum/showthrea...ler-27523.html

http://ecomodder.com/forum/showthrea...ing-32190.html

There exists on this site a picture of a box van car hauler trailer with a split-gate clamshell rear opening boat tail, but scanning 20 pages of searching results didn't turn it up. I used [aluminum trailer boat tail -single] as a search criterion. The above is your consolation prize.

As promised!

https://s26.postimg.org/4e269ge55/image1.jpg
https://s26.postimg.org/pozqdpw9l/image2.jpg
https://s26.postimg.org/p0qvurxjt/image3.jpg

That square front isn't helping at all. How about a small bubble up high on the front.

Dear gawd. It's a brick! a 2000lb brick!

First observation: You're moving a 4700lb SUV with a 3.6l V6 (unless there's other variants), which is barely adequate for the job. Then you add another 2000lbs in the shape of a huge brick. You're lucky you're getting 10mpg. You're lucky you can pull it at all.

In this case, unlike most others, a bigger engine would probably get better fuel economy. You don't have the excessive amount of torque necessary to move such a big load, so the engine has to make up for it by revving higher than a V8 would, and throwing your engine out of the efficient operating zone. So you're pissing away extra gas to compensate.

The weight is a bit of a concern as well. An extra ton added to any vehicle is going to be hard on the fuel mileage. But you can't do much about that or about your engine, unless you want to change vehicles and or the trailer. I'm assuming not...

So. You're down to aerodynamics, basically. Do something about that "brick" shape....more than the slight boat tail you've got pictured. Fix the front. Fix the rear.

Said simply, though it isn't going to be a simple job. Might not be worth the time and effort, unless you do a lot of driving with it.

Those square sharp corners are killing your gas mileage. Get at least a four inch radius on the side and top leading edges. This would be relatively easy to do by adding a bubble to the front. Ideally, all edges would be rounded, but the front edges are most important.

Another thing we need to know is the speed at which you are towing, I have towed a 5x8 Uhaul across the country at speeds up to and speed controlled at 95MPH, got 10MPG doing it with a 2000 ranger super cab 4x4 4.0L V6 with a cab level camper shell, had the truck locked in drive and went on, so as I have said, what speed are you towing at?

Apparently you have, instead of a boat tail, a stepped box cavity. The 'next' step should be finishing the fourth side.

But now I want to see a picture with the entry door open, to see how that works.

A bubble or wedge front face would work, but Great Success was had here by Hersbird:

http://i59.tinypic.com/k9dqhu.jpg
http://ecomodder.com/forum/showthrea...tml#post481517

Jacknife your rig and observe the clearance you have. If it's inadequate use an ogive curve.

Thanks
 

First of all I'd like to thank everyone for the input, especially babydiesed for the help. Ok, now it is a v-nose trailer (just hard to tell by the pictures) and how I came up with the size, angle, and placement was by researching tractor trailer aerodynamics which I basically am. Again this is a camper used in the real world. It would not be feasible to cover my lights or to have a 10' tail sticking out the back. I'm just an old retired guy with plenty of time to mess with things. Please keep the comments coming, and like I said, I didn't try it out yet but we should be going camping by the end of the month and we will see what happens.

Thanks again

I strongly disagree that the GM 3.6 LLT v6 is not adequate in that vehicle. Our traverse is every bit as fast and powerful as my cts.

http://gmpowertrain.com/2014_images/...art_acadia.jpg

I can't speak to the trailer.... but it is a fairly large trailer for a v6 SUV.

I'm curious, what gear does the vehicle stay in when towing? Are you manually limiting the top gear with the selector on the shifter?

Gear
 

At 70mph I'm in fourth gear, sometimes into fifth, at 55 mph, fifth gear. I'm hoping to get it running in fifth,and sometimes in fourth ( uphill and passing).

Now that you mention it, the V'd front is visible in the shadow. I assume the box cavity halves swing with the door?

Given your restrictions, the opportunity is in the wheelwells and underbody. for instance the A-frame that reaches back 3-4ft under the body could be filleted on the backside. The roof vent could have a perforated metal boat tail.

http://i56.tinypic.com/netkz8.jpg
http://ecomodder.com/forum/showthrea...tml#post250241

While ChazInMT was suggesting an open box boattail, I think using perforated metal would allow ventilation in and out when you're camping, but direct air flowing over the roof at speed.

Exactly. We're walking about with a trailer. That engine might be perfect for the SUV alone, but adding 2000lbs and terrible aero is too much for said engine, imo.

Here's a 6.2l silverado with a 7000lb trailer, of similar shape, getting 10.9mpg:
https://www.youtube.com/watch?v=8KN5juXz8CE

All I am saying is that 3.6l has to work a heck of a lot harder than a V8 would. And when you use an engine near it's (torque) limits, it pushes it out of the efficient area of it's bsfc.

True enough that with VVT and direct injection, they might, theoretically, be just as efficient at full torque, but historically gasoline engines always run richer at full engine torque than they do at, say, 80% torque.

Have you tried allowing it into 6th?

It won't go into 6th, not even manually

Trailer weight
 

I can roll this trailer around by hand on cement, also I pull 2000#s of snowmobiles pretty effortlessly, so I'm sure it's more of an aerodynamic issue. We'll see when I take it out for a spin.

even my 75hp/116Nm crapbox can pull 2000 lbs. But it won't do it fast :D

Its the aero that limits your mileage for your car.

You have adequate torque.

The fact it won't shift into 6th is telling you it is working to pull it at those speeds. I think these modern V6s can pull something like that just fine, but they will need the lower gears and they will take a big MPG penalty. Still you wouldn't get much better, maybe worse with a V8 and the rest of the time your mpg will certainly suffer. Now I was able to squeak out 14 mpg with that Hi-Lo pictured but that was at 60 mph but it is lower than the roof of the SUV we towed it with. It is also 5000 pounds loaded but once your moving it's mostly aero. Going faster, 65 maybe 70, with some hills we only got in the 12's. The average v8 gas pickup, towing the average camper out there is getting probably 6-9 mpg so 10 ain't bad. Slow down and see what you get at 60 mph.

If the sharp edges are bad. Then after a front bubble, could you simply take pvc pipe and slit down the length and glue that over the long side sharp edges to round them?

I realize that this might look funky. But a rounded edge made of pvc pipe glued over the sharp edge has to be better than the sharp edge alone. Am I right?

it doesn't matter if the power is coming from a 4 cylinder or v12. power is power. that's such an overstated myth it's ridiculous. I used to pull 3500LBS with my 2.2L 4 cylinder in my Saturn sedan just fine, and could even manage to stay in 5th (top) gear most of the time on the highway. even got 28MPG doing it. but, I also only went 55 while doing it.

The traverse, the 3.6, and the 6 speed transmission can all tow just fine, up to 5000LBS. There is more than enough power for that trailer.

the problems I see: that's not much of a V on the front of that trailer (not much you can probably do about this); the bottoms of trailers are usually really bad and create a lot of turbulence and drag, so smooth the underside; that isn't a proper use of the rear end treatment, semis usually use this technique on the back of trailers, but they need to be at the outer edge to be most effective; decrease your speed, you are going way faster than he aerodynamics of that trailer can support; and flat wheel covers.

So we no longer care about where we operate on our BSFC maps? Operating at 320 g/kwh is going to be just as efficient as operating at 250g/kwh?

As long as his truck isn't shifting into lower gears to maintain speed, a smaller engine operating at higher load will more often be in it's efficient range. The best BSFC for any engine is always at a very high load. That is why we have to PnG to use it. Unless we are pulling a heavy trailer.

Does your traverse have the roof mounting for luggage? I wonder if you could come up with a deflector to keep air from slamming the front/top of the trailer?

I would look at closing in the wheels, skirts on the trailer, and smooth bottom on the trailer.

The traverse is fairly aero and that trailer is not. The front of the trailer is significantly larger than the rear of the traverse.

Can you snap a few pics of it hitched?

10mpg
 

You know, I do have a roof rack, and an air deflector could be a good idea. I'm going to wait and see what difference the tail makes before I do anything else. The research I have done has shown me the tail should be 2' long, 10 degrees of deflection, and within 6" of the outside edge. Which is where I am at.

A single slit would produce a raising, 3/4-round edge. Two slits and butting the halves would produce a half-round. Then it's down to the 4%-of-gross-width rule, generally ~4".

ksa8907 — Closing the gap is non-trivial.

So, after towing with my acadia, I would say work on the aero of the car, too. the underside of the earlier lambda cars was less smooth, so an underbody panel would help.