Myth Busters

[djb383]

Don't know if it was a new episode or not but last night they did the magnets on the fuel line and acetone in the tank (for increased mileage), both were BUSTED. MacGags old french fry oil worked well in a diesel Mercedes though.

[the1stacekiller]

Great show watch it all the time.

[GrayFox]

For all you truck drivers out there another good gas mileage related episode is the one where they BUSTED the driving with your tail gate down.

[silver_vibe]

Quote, originally posted by ANO_Vibe »For all you truck drivers out there another good gas mileage related episode is the one where they BUSTED the driving with your tail gate down. I wonder if that's true about tonneau covers also...my sister swears her mileage went up 1-2 mpg when she got her hard tonneau. If the tailgate down myth is false, it makes me question the tonneau working also.

[VforVIBE]

Quote, originally posted by ANO_Vibe »For all you truck drivers out there another good gas mileage related episode is the one where they BUSTED the driving with your tail gate down. I can't stand people driving with the tail gate down, I don't know why, but don't they think the people who design the trucks look at stuff like that?

[djb383]

I thought hard tonneau covers weighed several hundred pounds and the added weight would lower mileage, maybe not.

[Mavrik]

those guys rock. I watch that show when ever I can. Didn't the truck with the tailgate down actually run out of gas first?

[VforVIBE]

Quote, originally posted by Mavrik »Didn't the truck with the tailgate down actually run out of gas first?yes... that was why the myth was busted.

[Jahntassa]

Quote, originally posted by silver_vibe »I wonder if that's true about tonneau covers also...my sister swears her mileage went up 1-2 mpg when she got her hard tonneau. If the tailgate down myth is false, it makes me question the tonneau working also.I think with the tonneau the air has less distance to travel down, less drag kinda thing. It might still have a 'bubble' just behind the window, just a lot smaller. Of course I don't know much about physics and don't have a wind tunnel to try the theory, but just an idea!

[TJinPgh]

Hmmm. I didn't see the ep. How, exactly, did they conduct the test?

[VforVIBE]

Tailgate: Up or down?Myth: Driving your pickup with the tailgate down gives you better fuel efficiency than with the tailgate up.Test SetupAdam and Jamie were each given identical, new model pickup trucks. They both had equal mileage, same tire pressure, and 30 gallons of gas. Jamie drove with the tailgate up and Adam the tailgate down. The rules:They have to maintain the speed limit All acceleration must be done by cruise control No drafting Windows up, A/C must be exactly the same in both cars The TestAfter 300 miles there didn't appear to be much difference in the gas consumed, but after 500 miles Adam (tailgate down) ran out of gas. Jamie made it another 30 miles before he ran out of gas. This result was the exact opposite of the myth.Water tunnel visualizationAccording to the experts, a circular pillow of air forms behind the cab of the truck when the tailgate is up. This "separated bubble"/"locked vortex flow" keep the faster moving air from contacting the truck, and thus reduces drag. With the tailgate down, the bubble breaks down and is no longer able to keep the fast moving air out, increasing drag. In their scale model with the water tunnel, they were able to see that the increased drag. With the tailgate down, the particles in the water were dropping down and hitting the tailgate.mythbustedTailgate Up or Down Revisited: Mesh tailgate, hardcover, tailgate removalFor the original myth they did a driving test and a water vortex test, both of which showed that you save more gas with the tailgate up. Their viewers suggested that they test three new conditions:Hardroof cover over pickup bed Mesh tailgate Remove the entire tailgate They had a much simpler test setup this time. They had an electronic flowmeter hooked into fuel line of Jamie's pickup. Adam: "For anyone out there that wants to e-mail telling me that we screwed up this test, we have already calibrated this thing, to this car. So it's going to be perfect!" They drove the pickup truck up and down the stretch of 101 around Candlestick and the Cow Palace.Tailgate down: 5.2 gallons/hr @ 55mph. 1.2 gallons/hr @ 25. Tailgate up: 5.0 gallons/hr @ 55mph. No reading for 25mph given, but tailgate up was once again confirmed as more efficient. Hardcover over pickup bed: 5.0 gallons/hr @ 55mph. 1.2 gallons/hr @25mph Tailgate mesh: 5% more efficient Tailgate removed: about the same as tailgate up and hardcover Mesh was most efficient by 5%still bustedsummaries of all the episodes can be found at: http://kwc.org/mythbusters/

[TJinPgh]

Thanks for the fast reply. It confirmed my suspicions.Sorry, but this "test" is not in any way scientific. It makes an assumption that quite simply isn't true.It assumes that two vehicles, the same model, same mileage, same options, driven the same exact way will get the same mileage. Sorry, but thare are enough people on this forum wondering why they get 30mpg driving 60mph while somebody else gets 36mpg for us to know that this is categorically untrue.Ever look at an EPA fuel economy result sheet? They can't even duplicate the same exact results on a test track with the SAME vehicle most of the time, let alone trying to do it with multiple vehicles.Look at the highway results for the 03 Vibe. The EPA AVERAGE is 33mpg. But, it says right on the EPA sheet that it ranges from something like 28 to 36 highway.Further, unless they found a completely straight road where the two trucks could ride side by side for the entire run, the test becomes invalid because of variations in drag.The BEST one could hope for in conducting this test as a myth buster would be to use the same exact vehicle and run the test several times in each configuration and take an average.Even then, you still have things such as weather (temperature, wind conditions, etc) that play a factor.I'm not saying the myth is accurate or not. I'm simply suggesting that unless they can explain why a mesh tailgate or a tailgate that's removed gets better than with the tailgate down, the results don't make sense.With respect to the magnets and acetone. While I've heard from too many people who have tried the magnets unsuccessfully to believe they work (and from enough people who have done the acetone tests to know results vary greatly with HOW you use it, and the vehicle used in), a similar problem would exist.

[VforVIBE]

Ok, then show me something "scientific" that says other wise, like you stated, it's not possible to get the exact same conditions and what not, but as I said before, don't you think the designers would look in to aerodynamics of the truck? They're not going to build something that would have a big drag on it...at least I hope not

[GrayFox]

that's about the best test you could do. There are far too many variables in the real world to consider. Given that the truck with the tailgate down ran out of gas first doesn't necessarily mean that it does anything totally super bad to your mileage it just says that it doesn't do anything good for it, so why drive with it down? a variation of +/- 1 MPG in a test like this can make a big difference. But it could be something else (or a lot of different things) affecting the mileage of the truck. Like I said they proved that driving with your tailgate down doesn't improve the aerodynamics of the truck and therefore doesn't improve gas mileage... BUSTED lol

[TJinPgh]

Quote, originally posted by VforVIBE »Ok, then show me something "scientific" that says other wise, I'd guess the water tunnel simulation they ran would be about as close to perfect as you could get. Like I said, I wasn't suggesting their conclusion was wrong, just that the road test wasn't valid.Quote »but as I said before, don't you think the designers would look in to aerodynamics of the truck? They're not going to build something that would have a big drag on it...at least I hope not One would think, but it's an assumption that I'm not sure I would make.For, example, if adding a CAI can increase performance while (if driven conservatively) not affecting fuel economy negatively, then why don't they include them on every car?If those big a$$ wings on the back of a car have any positive effect on a vehicle, why don't they include them?The design of a car (that is intended to be sold) includes a lot of factors that may not always be optimum with respect to one performance aspect or another.Most companies don't include things such as CAI or performance exhausts, not because they'd add anything substantial to the production costs of the car, but because the loss of sales generated from the increased noise factor would likely be greatern than the increase of sales any performance gain would yield.The truck without the tailgate yielded the same results as the truck with the tailgate up (which calls their water tunnel results into question, IMHO). Yet, while I HAVE seen dealers offer aftermarket mesh tailgates, I've never seen one offer to cut costs to the buyer by ordering a truck w/o a tailgate.Why? Because, in the over all scheme of the intended use of a truck, one without a tailgate is pretty much useless. Beyond that, you just sort of EXPECT a truck to have a tailgate. Selling one w/o one would seem like cheating the buyer of something their entitled to.What sells dictates design and features far more than any advantage a single feature may yield, unless it can be proven that having that feature is what is generating the sales to begin with.If it could be proven removing the tailgate would add 5mpg consistently to a truck, I still doubt you'd see many designed or sold w/o them.

[VforVIBE]

Quote, originally posted by TJinPgh »If those big a$$ wings on the back of a car have any positive effect on a vehicle, why don't they include them?because the cars that those wings are on (FWD) don't need them and do not a thing for the cars, except make them look UGLY.

[JohnC]

My favorite myth busters test...banned for television.http://www.youtube.com/watch?v=WtJIZvlwzZg

[djb383]

Dude, tooooooo funny!