"Mythbusters" - Drafting with the Hemi! - Jeep Commander Forums: Jeep Commander Forum
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post #1 of 21 (permalink) Old 07-28-2008, 01:13 PM Thread Starter
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"Mythbusters" - Drafting with the Hemi!

...so I'm watching Mythbusters and they're doing a section on "drafting" a semi truck. Long story short...they started at 100' and worked up to less than a foot from the trailer. The technique works execptionally well. The show got about 40% better fuel economy.

so

During our drive to Orlando from Atlanta recently, I decided to try it for myself. I selected "avg/mpg" and hit reset while I was steady at 75mph on my own...no drafting. Got a whopping 15-16 mpg. ugh. Then I found a semi moving at a pretty good speed, got behind him and set the cruise control. Hit reset again and after a while, I was getting 19.7-20/mpg! I was about 4-6 car lengths behind. The problems are this, you gotta constanly hit "accel" or "de-accel" on the steering wheel to tweak your speed to match his...each button press is 1/mph of change. Hills don't help things...those trucks don't maintain speed too well on ups and downs. But it gives you something to do on the drive.

The other problem is finding an 18wheeler that isn't going 55-60. I just can't purposely go THAT slow while everyone else is whipping by at 75-85.

Thought I'd pass this along to you guys...

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post #2 of 21 (permalink) Old 07-28-2008, 03:10 PM
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I saw that episode a few months ago. You have to drive insanely close (tailgating) to realize signficant gains, which is probably a really bad idea unless you have a death wish!

Seriously, why risk it to save a few MPGs?
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post #3 of 21 (permalink) Old 07-28-2008, 03:22 PM
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4-6 car lengths, I wouldn't consider a "death wish".

That's a pretty good improvement you got, Hemi! The highways around here are FULL of semi's that seem to always break the speed limiits, so finding one going faster than 55-60 is no problem at all. Thanks for the info.


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post #4 of 21 (permalink) Old 07-28-2008, 04:58 PM
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I agree that this is a great idea for a long drive to save money. Semitrucks have a much longer stopping distance than any XK on the road, even if they lock up the brakes at highway speed 4-6 car lenghts should be safe. Keep in mind another Mythbusters I saw where they tested the effects of a semitrailer tire when it explodes. The myth was based on a trailer tire being fatel for a motorcycle. They also proved it could go through a car window and decapitate you! I would make sure the trailer you are following looks pretty new.

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post #5 of 21 (permalink) Old 07-28-2008, 05:20 PM
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IIRC, they only proved it could, with some wild combination of circumstances. They couldn't cause any harm in a real world circumstance. Again, that's if I recall correctly.
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post #6 of 21 (permalink) Old 07-28-2008, 05:25 PM
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Just the chance of another rock chip / broken windshield is going to keep me back. Gas is cheaper than glass.
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post #7 of 21 (permalink) Old 07-28-2008, 06:31 PM
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I agree, and being that close to a semi is dangerous.

BTW, where in CR are you turbo?

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post #8 of 21 (permalink) Old 07-28-2008, 07:29 PM
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Truck drivers hate this. If you draft behind them for a while they will start swerving back and forth to shake you off. Personally, when driving a long distance I prefer to look at scenery other than the back end of an eighteen wheeler. I also like to see well in front for safety reasons.

4-5mpg increase is not going to affect my lifestyle but an accident might.
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post #9 of 21 (permalink) Old 07-28-2008, 07:43 PM Thread Starter
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I'm not so close that it should bother them. They draft each other at similar distances or even close..I've seen. On a 500 mile drive, 5mpgs can make a difference. And those of you worried about fod from the road...rocks can/will bounce whether you're at 4 car lenths or 14 at highway speeds...even from a car. Just don't draft a dump truck.

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post #10 of 21 (permalink) Old 07-28-2008, 08:22 PM
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I try to avoid large trucks when I'm driving. Too much to go wrong with debris, blown tires and the like, plus many modern drivers aren't very good. Not the same professionals that used to drive 20-30 years ago. ..
I'm just wondering when we'll see some yahoo figure out a way to attach their car to the back bumper of a semi-trailer.. Imagine a tow bar with some sort of remotely controlled coupler that could grab the bumper.. Kinda like those remote control arms on submarines..
I don't think it would be all that hard to do, the technology wouldn't be any more sophisticated than what's used on snowplows.
One could just hook up to a trailer and let go of the wheel.. Plus get really outrageous mileage..
I sure wouldn't want to be attached to the trailer like that though..
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