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Old 05-12-2017, 07:52 PM   #11 (permalink)
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Quote:
Originally Posted by Stubby79 View Post
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.

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.



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

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Old 05-12-2017, 08:00 PM   #12 (permalink)
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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?
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Old 05-12-2017, 08:38 PM   #13 (permalink)
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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).
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Old 05-12-2017, 08:47 PM   #14 (permalink)
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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.


Aero RV (custom boat tail for '95 Ford E-350 Class C motorhome)

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.
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Old 05-12-2017, 10:01 PM   #15 (permalink)
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Quote:
Originally Posted by ksa8907 View Post
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.

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


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.
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Old 05-13-2017, 09:01 AM   #16 (permalink)
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Quote:
Originally Posted by Stink View Post
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).
Have you tried allowing it into 6th?
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Old 05-13-2017, 09:40 AM   #17 (permalink)
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It won't go into 6th, not even manually
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Old 05-13-2017, 11:22 AM   #18 (permalink)
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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.
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Old 05-13-2017, 01:46 PM   #19 (permalink)
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even my 75hp/116Nm crapbox can pull 2000 lbs. But it won't do it fast

Its the aero that limits your mileage for your car.

You have adequate torque.
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Old 05-13-2017, 08:03 PM   #20 (permalink)
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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.

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