Myth buster

POLO · Post by **POLO** » Mon Nov 07, 2005 10:13 am

In one of their show,they test if window open consume more fuel or window close with the ac open.So,the bring two exactly the same SUV,they remove the gas inside completely,adding exactly 5 gallon of fuel.Ten they roll non stop about 7 houres at 45 mph.So,the SUV who have window close and ac open went down of fuel first,then the SUV with the window open.So,it's more fuel economy to window then the ac.

BlueCrush · Post by **BlueCrush** » Mon Nov 07, 2005 10:20 am

I have only seen a few episodes, but I did see that one. It kind of makes sense though. The engine works harder to run the compressor than to work against wind drag/resistance.

JohnC · Post by **JohnC** » Mon Nov 07, 2005 10:30 am

Quote, originally posted by POLO Â»So,the SUV who have window close and ac open went down of fuel first,then the SUV with the window open.So,it's more fuel economy to window then the ac.In thier case yes. What about a different body style (drag coeffeint) or a much bigger factor...speed. As the vehicle speed increases the drag from the open window goes up exponentialy.Interesting show...I liked thier plane crash passenger position experiments.

GMJAP · Post by **GMJAP** » Mon Nov 07, 2005 10:33 am

45mph or so is about the cutoff point. Below this, you're better off opening windows. Above this, you'll get better mileage with the AC as the drag from the open windows becomes significant.They did this test with an SUV, which have the aerodynamics of a brick. Thus, the tradeoff speed will be higher as the open windows don't affect the aerodynamics as much as they do with a sedan or coupe.With the AC on, you're still pushing that brick through the wind, plus having to run the compressor.Edit JohnC posted while I was typing. Saying essentially the same things.

ZubenElGenubi · Post by **ZubenElGenubi** » Mon Nov 07, 2005 10:49 am

Quote, originally posted by JohnC Â»What about a different body style (drag coeffeint) or a much bigger factor...speed. As the vehicle speed increases the drag from the open window goes up exponentialy.Just to be clear, the drag force on any moving object is proportional to the square of the velocity; it is not exponential. Here's the formula:D="Drag" force S ="Frontal" area (cross-sectional)V ="Velocity" = Density of airCd = Drag coefficient

mcgusto82 · Post by **mcgusto82** » Mon Nov 07, 2005 12:01 pm

a better test would've included a higher speed run. around here the average highway speed is 60mph. in VA where i used to live, it was 70+1/3 mph. 45 is more like major street driving.

BOZACK · Post by **BOZACK** » Mon Nov 07, 2005 1:35 pm

I would rather ride with the ac. I can here the radio better.

ragingfish · Post by **ragingfish** » Mon Nov 07, 2005 1:38 pm

Odd.I saw that same episode, but I could SWEAR the open windows were found to be less efficient then the A/C?

Mr. Poopypants · Post by **Mr. Poopypants** » Mon Nov 07, 2005 1:45 pm

Quote, originally posted by ZubenElGenubi Â»Just to be clear, the drag force on any moving object is proportional to the square of the velocity; it is not exponential. Here's the formula:D="Drag" force S ="Frontal" area (cross-sectional)V ="Velocity" = Density of airCd = Drag coefficientOUCH, now my head hurts.

russ257 · Post by **russ257** » Mon Nov 07, 2005 9:48 pm

yeah who drives 45 the test should be replicated with 10 mph incraments up 85

joatmon · Post by **joatmon** » Tue Nov 08, 2005 1:19 am

I saw a subsequent episode of myth busters, one where they responded to viewer compliants and retested a bunch of previously tested myths, the AC vs windows being one of them, and they determined that at higher speeds the AC was better, at lower speeds the windows were better.Quote, originally posted by ZubenElGenubi Â»Just to be clear, the drag force on any moving object is proportional to the square of the velocity; it is not exponential. Here's the formula:D="Drag" force S ="Frontal" area (cross-sectional)V ="Velocity" = Density of airCd = Drag coefficientI used to do math, and it's been a while, but I thought an equation involving a square of a variable was "exponential". Certainly not linear. Where is SgrPlum, she's the math teacher here.

MadBill · Post by **MadBill** » Tue Nov 08, 2005 1:24 am

Quote, originally posted by joatmon Â»I saw a subsequent episode of myth busters, one where they responded to viewer compliants and retested a bunch of previously tested myths, the AC vs windows being one of them, and they determined that at higher speeds the AC was better, at lower speeds the windows were better.I used to do math, and it's been a while, but I thought an equation involving a square of a variable was "exponential". Certainly not linear. Where is SgrPlum, she's the math teacher here. Another nit to pick, Zube: The drag increases with the square of the speed, but the power requirement increases as the cube.

mcgusto82 · Post by **mcgusto82** » Tue Nov 08, 2005 2:09 am

when the retested the myth. did they include the hair factor?obviously, us ethnic folk don't deal with wind in our hairs well. i usually ride with thw windows up. reqardless of speed. you have to when you spend 10 minutes getting your hair to the right position. (growing hair)

northvibe · Post by **northvibe** » Tue Nov 08, 2005 2:54 am

Ive done this in the vibe, when driving from duluth to the twin cities.Speed limit on hwy 35 is 70, i usually go 79mphwith windows up and AC on low i got better mileage than with the windows down.Oh does anyone else get a pulsating air noise with the back windows down?? like with the rear windows down i cant drive becuase it hurts my ears so much, and its this pulsating noise..yea its odd.

Mr. Poopypants · Post by **Mr. Poopypants** » Tue Nov 08, 2005 2:57 am

Quote, originally posted by MadBill Â»Another nit to pick, Zube: The drag increases with the square of the speed, but the power requirement increases as the cube.(pi)R^2NO(pi) R Round Cake R^2Sorry it was getting a little mathy in here, had to lighten up the mood.Quote, originally posted by northvibe Â»Oh does anyone else get a pulsating air noise with the back windows down?? like with the rear windows down i cant drive becuase it hurts my ears so much, and its this pulsating noise..yea its odd.Yep, just crack another window or 2, this will allow the air to flow through the car instead of the pressure causing the thumping sound that kills your ears.

Atomb · Post by **Atomb** » Tue Nov 08, 2005 3:01 am

Quote, originally posted by northvibe Â»Oh does anyone else get a pulsating air noise with the back windows down?? like with the rear windows down i cant drive becuase it hurts my ears so much, and its this pulsating noise..yea its odd.open one front window and the opposite back window to eliminate this problem.i usually open the driver's window and the rear passenger side...for maximum cooling with no pulsing!oh and to keep it 'mathy'...the ratio of openess isn't 1:1...i'd say for a fully open driver side, the opposite rear should be open to about 1/3 (or 33.333%) adjust exponentially for any other openess value on the front window! (sorry, couldn't resist!)

BigMac · Post by **BigMac** » Tue Nov 08, 2005 3:03 am

Quote, originally posted by northvibe Â»Oh does anyone else get a pulsating air noise with the back windows down?? like with the rear windows down i cant drive becuase it hurts my ears so much, and its this pulsating noise..yea its odd.Yes... I had my car broken into, and the broke the rear window so I had to drive with it "open" I had to open the front windows so that there would be air flow, and that reduced the sound, but that was one windy/cold drive. I will never drive with only one rear window open... it's very uncomfortable.

BOZACK · Post by **BOZACK** » Tue Nov 08, 2005 3:06 am

Quote, originally posted by northvibe Â»Oh does anyone else get a pulsating air noise with the back windows down?? like with the rear windows down i cant drive becuase it hurts my ears so much, and its this pulsating noise..yea its odd.Yes, we all get it. But it is not exclusive to the Vibe. My brothers Tuscon does it as well as my cousins Dodge pickup.

MadBill · Post by **MadBill** » Tue Nov 08, 2005 3:21 am

It's caused by a phenomenon called Helmholtz resonance and the frequency can be predicted by... you guessed it: Another Equation! (with which Zube, Poopy and I will forbear from boring you all...)Now I R Pi-faced...

ZubenElGenubi · Post by **ZubenElGenubi** » Tue Nov 08, 2005 4:05 am

Quote, originally posted by joatmon Â»I used to do math, and it's been a while, but I thought an equation involving a square of a variable was "exponential". Certainly not linear. Where is SgrPlum, she's the math teacher here. An exponential curve is always expressed as a variation of this basic function:where, the number "e" is the Euler number (about 2.718).On the other hand, the drag force function, is a "power" function, simply because there is an exponent involved ("2"...in v squared)

joatmon · Post by **joatmon** » Tue Nov 08, 2005 4:11 am

I used to be really good at math, then they invented the number eleven, and I was never able to keep up after that

Mr. Poopypants · Post by **Mr. Poopypants** » Tue Nov 08, 2005 4:33 am

Quote, originally posted by joatmon Â»I used to be really good at math, then they invented the number eleven, and I was never able to keep up after thatPreach!!!I am bad at math, never was good, never will be. It's all too boring to me.

Atomb · Post by **Atomb** » Tue Nov 08, 2005 4:36 am

Quote, originally posted by joatmon Â»I used to be really good at math, then they invented the number eleven, and I was never able to keep up after thatfor me it was 21. ...but i had to take my shoes off and pull down my pants!

redlava · Post by **redlava** » Tue Nov 08, 2005 10:49 pm

The new one this week is going to have one on steel toed shoes. That should be pretty interesting considering that I wear those everyday. We will see how much danger I will be in having my toes cut off. Oh wait I can't cause Lost is on at the same time. Darn it.

gargoyle · Post by **gargoyle** » Tue Nov 08, 2005 10:58 pm

I tried to do Math once... I tried to multiply. But the wife wouldn't cooperate.

Mr. Poopypants · Post by **Mr. Poopypants** » Tue Nov 08, 2005 11:11 pm

Quote, originally posted by redlava Â»The new one this week is going to have one on steel toed shoes. That should be pretty interesting considering that I wear those everyday. We will see how much danger I will be in having my toes cut off. Oh wait I can't cause Lost is on at the same time. Darn it.Tivo/DVR is a beautiful thing.I'm sure someone will let you know what happens. What night is that on anyway? I'll record it (if I remember) and let you know.

Baltovibe · Post by **Baltovibe** » Tue Nov 08, 2005 11:26 pm

Quote, originally posted by Mr. Poopypants Â»What night is that on anyway? I'll record it (if I remember) and let you know.According to Discovery.com (MythBusters Steel Toe Amputation) ...NOV 09 2005@ 09:00 PM ESTNOV 10 2005@ 01:00 AM ESTNOV 13 2005@ 01:00 PM ESTNOV 25 2005@ 03:00 PM ESTNOV 29 2005@ 10:00 PM ESTNOV 30 2005@ 02:00 AM ESTThink you can catch one of them?

Mr. Poopypants · Post by **Mr. Poopypants** » Tue Nov 08, 2005 11:36 pm

I'm going to write myself an email to remember it.

ZubenElGenubi · Post by **ZubenElGenubi** » Wed Nov 09, 2005 6:46 am

CNN/Money did some tests on various gas saving tips; one of them was the windows vs A/C test @ 65MPH. They noticed little difference.http://money.cnn.com/2005/09/0...x.htm

POLO · Post by **POLO** » Wed Nov 09, 2005 7:41 am

Nice find

redlava · Post by **redlava** » Wed Nov 09, 2005 10:56 pm

Quote, originally posted by Baltovibe Â»According to Discovery.com (MythBusters Steel Toe Amputation) ...NOV 09 2005@ 09:00 PM ESTNOV 10 2005@ 01:00 AM ESTNOV 13 2005@ 01:00 PM ESTNOV 25 2005@ 03:00 PM ESTNOV 29 2005@ 10:00 PM ESTNOV 30 2005@ 02:00 AM ESTThink you can catch one of them? I got the week off so I can probably view at least one of those.

Baltovibe · Post by **Baltovibe** » Thu Nov 10, 2005 1:55 am

Quote, originally posted by redlava Â»I got the week off so I can probably view at least one of those. I won't spoil the surprise, but it was very interesting watching the testing and the results!

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