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Old 01-28-2023, 03:51 PM   #1
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Default Efficiency Test - When?

I've been browsing all of the brochures and everyone I've come across says it's 77% more efficient than the Fleetwood Terry and it was done by the transportation research center of Ohio. I can't seem to find any information on that test though, or when it was performed.

Does anyone happen to know?
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Old 02-02-2023, 03:20 PM   #2
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Hi lo published a brochure with those stats

https://hilotrailer.com/pdfs/2001-classic.pdf

page 4 & 6
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Old 02-02-2023, 06:04 PM   #3
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Hi lo published a brochure with those stats

https://hilotrailer.com/pdfs/2001-classic.pdf

page 4 & 6
Yea, I saw as early as the 60s they started quoting as much as 5mpg. Then in the 70s they had the percentages. And 200s started citing the study with the same numbers. I was more looking for the actual test to see what they tested, methods, etc. just interested in reading the text than just the results.
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Old 02-02-2023, 10:16 PM   #4
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I just did a search for Transportation Research Center, Inc. and it's a genuine company that specializes in automotive related testing. You could possibly contact them with your questions regarding the actual test protocols, but that link DID say the two trailers were pulled with the same tow vehicle, at the same speed over a test track.

Knowing what I learned in my study of Aerospace Engineering at Ga Tech, wind drag force increases according the the square of the vehicle's speed. And our trailers don't add a lot of "flat plate drag" to the system, the way a trailer that sticks way up above the tow vehicle does. My trailer causes a drop in my F150's fuel economy of between 1-2 mpg (calculated) when towed at 65 mph on a trip.

- Jack
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Old 02-03-2023, 01:27 AM   #5
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Originally Posted by JackandJanet View Post
I just did a search for Transportation Research Center, Inc. and it's a genuine company that specializes in automotive related testing. You could possibly contact them with your questions regarding the actual test protocols, but that link DID say the two trailers were pulled with the same tow vehicle, at the same speed over a test track.

Knowing what I learned in my study of Aerospace Engineering at Ga Tech, wind drag force increases according the the square of the vehicle's speed. And our trailers don't add a lot of "flat plate drag" to the system, the way a trailer that sticks way up above the tow vehicle does. My trailer causes a drop in my F150's fuel economy of between 1-2 mpg (calculated) when towed at 65 mph on a trip.

- Jack
I have an email out to them, so hopefully they respond so I can geek out a little.

So based on your background what are your thoughts on the aerodynamics of the towlites vs the classics? The classic have the rounded caps and lower skirts but are generally taller and wider.

Also, does length matter given all the rest being the same? If you’ve already punched a whole through the air, how much more drag is there?
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Old 02-03-2023, 09:01 AM   #6
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Length has a small effect due to "skin friction drag", but that is really minor at the speeds we're working with. It's much more significant when you're looking at speeds aircraft experience.

The front of a HiLo is essentially a "flat plate" that would cause very high drag by itself if it were not essentially "hidden" behind the tow vehicle. The space between the tow vehicle and the trailer is what's known as a stagnation zone where the air is sort of moving along with the two vehicles. I say "sort of" because this is not perfect - there is turbulence there and some drag generated in this zone.

Now, any part of the trailer that extends wide or above the tow vehicle is exposed to the airflow that is coming off that vehicle and is a new potential "flat plate". Rounding this allows the air to move past the trailer with less drag - it smooths the airflow out a bit, but, if there is more frontal area, the drag will increase.

Lower skirts probably help reduce turbulence between the trailer and the road, which can reduce drag somewhat. An air dam under the bumper of a car or truck does much the same thing - it forms a stagnation zone under the vehicle that reduces the drag inducing turbulence that would form there. The drag that is reduced in this way is larger than the drag that is created by the frontal area of the air dam.

Now, I've simply told you how all these things work, without giving you ANY judgement of their effectiveness, because I have no way to calculate it. The theories involved in aerodynamics are actually pretty terrible and wind tunnel testing or track testing are needed to determine actual numbers.

- Jack
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Old 02-04-2023, 11:36 AM   #7
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Not scientific by any means, but perhaps a couple of mileage examples from personal experience are worth mentioning....

Number 1: Current '02 GMC Sierra (1/2 ton extended cab short bed, 220k miles, 5.3 V8, cab high camper shell, factory tow pkg, Belltech lowering kit), tow vehicle for our 2307C. When towing, we average about 14-15 mpg on level highways at 60-65 mph - about 2-4 mpg less than without the trailer. Camper shell was on the truck when purchased so no experience towing without it - suspect removing the shell would impact the "stagnation zone" Jack describes between the truck and trailer, increasing turbulence and the effective "flat plate" area of he trailer, with some resulting decrease in mileage.

Number 2: Years ago '79 Chevy Suburban (1/2 ton, 140k miles, 350 V8, 4 speed granny low manual trans) - daily driver, 60 miles per day freeway commute. Installed a Belltech lowering kit, front air dam and smaller mirrors about a year after purchasing the truck used - average freeway mileage went up from around 14-15 mpg to 18-19. With no other changes made, the only factor that would account for the improvement in fuel economy is drag reduction (never bought the trailer we intended to tow with the Suburban, so have no towing / non-towing mileage comparison).
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Old 02-05-2023, 01:10 AM   #8
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I tow a 2807C with a 2015 ecodiesel.. .over a 9000 mile trip from Oregon to Virginia and back, I averaged 16.7 mpg using cruise control set at 65 moh...
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Old 02-10-2023, 02:22 AM   #9
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Wow! Brianagee, That's an impressive gas mileage you're getting while towing a 28 footer.

I'm getting an average of 9-10 mpg towing my 2589RD. I know I'm overpowering my 2001 Ram 1500, but so far the Ram has been hanging in there tough. I try not to push it too much on any uphill grades; it tows the Hilo OK.
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Old 02-10-2023, 01:09 PM   #10
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It is amazing the difference between a gas v8 and a turbo diesel v6...I leave it on cruise up hill and down....
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Old 02-10-2023, 01:40 PM   #11
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It is amazing the difference between a gas v8 and a turbo diesel v6...I leave it on cruise up hill and down....
You've also got a much more properly "balanced" ratio between the towing engine/transmission combo and the trailer you're pulling.

I'm pulling a 17ft HiLo with my 3.5L Ecoboost and I leave it in cruise all the time too. I've never had the transmission go below 4 th gear going uphill, including the 12 mile 6-7% grade out of Camp Verde or the uphill pull going into Flagstaff from the north.

- Jack
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