import question

[Camaro Dom]

Re: import question

It actually makes sense. Its similar to people who own trucks opening the tailgate when doing highway driving, allows the air to flow more freely over the bed than with the gate up where it acts like a parachute.

Wisest thing to do in an Fbody....run the AC. With the windows down and/pr Ttops removed, the car acts more like a parachute, and take a little more gas to get the car up to speed and maintain it.

actually, mythbusters (episode 43) proved that keeping your tailgate UP during highway driving gets u better gas milage. Counter-intuitive? yeah, i know

this is the reasoning behind it: when u drive a truck with the tailgate up, the air in the bed is relatively calm (relative to the 65 mph winds around it). Thus, when you have the gate up, you create a smoother flow of air over the truck, and when you let it down, you dissipate that smooth airflow.
http://kwc.org/mythbusters/2005/11/e...s_cures_f.html

I'm goin out on a limb and saying that it's probably similar with f-bodies to some degree. Remember, the faster air moves, the lower the pressure (thats how we get lift from an airfoil), so realistically if your driving with the tops off and windows down, the air outside the car is moving by at 75 mph, while the air inside is stationary (from the point of view inside the car). This ideally should mean that air is getting sucked out as the higher pressure (stationary) air flows to the lower pressure (moving) air, so you wouldn't really be getting a "parachute" effect. but thats just my own logic...

[Camaro Dom]

Re: import question

the function makes sense, but there are ways' of accomplishing the same thing without holes in your bumper.. like a under body splash guard that sits flush to your bumper..which would actually work better than perforating your bumper anyway.

a MUCH better idea would be to take sheet metal and put a flat cover under the whole car. It'd create a bernoulli force, and suck the car closer to the road at higher speeds. indy cars and F1 used to do this for a while (i think it got banned tho). it'd work a heck of alot better than that stupid wing they like so much.

[Mogobs30th]

Re: import question

a MUCH better idea would be to take sheet metal and put a flat cover under the whole car. It'd create a bernoulli force, and suck the car closer to the road at higher speeds. indy cars and F1 used to do this for a while (i think it got banned tho). it'd work a heck of alot better than that stupid wing they like so much.

I know Indy car's are completely flat on the bottom, its actually part of the chassis. If you ever see the underside of an indy car, it looks like the body on the topside.

[camaroman1181]

Re: import question

the mythbusters episode was a joke btw.... they used crew cab trucks with the sub 6' beds... this would be the ideal situation where having the tail gate up or down would not matter... If they wanted to do a true test, they should have considered the extreme in the other direction... standard cab and an 8' box. And in all honesty, the only way they could really test this idea is to put them on rollers in a wind tunnel. or hell, just put models in a wind tunnel and calculate the drag... their "experient" was pretty flawed to say the least..

as for the holes on imports, yes.. that is correct.. supposedly stops the bumper from acting like a parachute and letting the air out... does it? probably not.. more than likely, it increases drag...

think of it this way.. take a glass. put it under a stream of water out of your faucet. once that glass is full, you arent really mixing and replacing the water at the bottom, the new stuff is pretty muhc just flowing off the water at the top and spilling over.. same kind of principle with the tail gate and bumper. once they are full of air, they do not take in a lot of additional air, rather the trapped air tends to deflect incoming air.

[HokieBird]

Re: import question

a MUCH better idea would be to take sheet metal and put a flat cover under the whole car. It'd create a bernoulli force, and suck the car closer to the road at higher speeds. indy cars and F1 used to do this for a while (i think it got banned tho). it'd work a heck of alot better than that stupid wing they like so much.

I think asking someone who puts a huge wing on a FWD car to create functional underbody aero panels is like asking vanbibber not to whore. It's not gonna happen.

[skorpion317]

Re: import question

I've always called those "speed holes". Most ricers around here have them, even if they're running a 17-second 1/4 mile.

I'm sure there's a better way to cut down on drag than drilling holes in your bumper.

[SpeedingFirebird]

Re: import question

Wisest thing to do in an Fbody....run the AC. With the windows down and/pr Ttops removed, the car acts more like a parachute, and take a little more gas to get the car up to speed and maintain it.

Mythbusters did an episode on similar to this as well (non-t-tops though). They wanted to see if gas mileage was better with the A/C on or the windows open. The concluson was that the car with the the AC on was 15% less efficient than the car with the windows down.

[Fireball27]

Re: import question

[QUOTE=Mogobs30th]It actually makes sense. Its similar to people who own trucks opening the tailgate when doing highway driving, allows the air to flow more freely over the bed than with the gate up where it acts like a parachute.QUOTE]

Not really. Theres aerodynamic reasons, but i'm at work so i can't explain now ;)

[Earnhardt132000]

Re: import question

I can't tell who is being sarcastic and who isn't.

[Vanquish]

Re: import question

Mythbusters did an episode on similar to this as well (non-t-tops though). They wanted to see if gas mileage was better with the A/C on or the windows open. The concluson was that the car with the the AC on was 15% less efficient than the car with the windows down.

Your conclusion is backwards. It was more efficient to have the a/c on then to have the windows down.

[StrtRacer98]

Re: import question

Your conclusion is backwards. It was more efficient to have the a/c on then to have the windows down.

I duno, im pretty sure it's the other way around...

Other than efficiency.. think of the mass power loss (mine at least) with the A/C on
Feels like im driving a hummer with a Geo tracker engine

[acwolfpack07]

Re: import question

yeah you can definately feel the pull on the engine with the ac on

[SpeedingFirebird]

Re: import question

"Urban puzzle": it is more efficient, on a hot day, to run with the A/C on and windows up than to run with windows down (b/c of increasing car's drag).

Computer-based mpg measurements:

* 11.7/11.8 with A/C on and windows up
* 11.7/11.8 with A/C off and windows up
* 11.3 with A/C off and windows down

So, according to the computer, it's better to use A/C with windows up.

This was too quick and easy for TV, so they decided to stage a seven hour marathon, race-til-you're-empty duel, with Jamie driving an SUV with A/C on and Adam driving an SUV with windows down. Though, once the safety inspector intervened, it was no longer a seven-hour marathon, it was a bit slower (45mph instead of 55mph), and a lot shorter (only 5 gallons each).

Jamie's A/C car ran out of gas first -- Adam's windows down SUV ran for another 30 laps -- completely contradicting the computer mpg estimate. Computer estimate based on air flow into the engine, so it would appear that it is unable to properly model the difference between A/C and windows down.

[Fireball27]

Re: import question

"Urban puzzle": it is more efficient, on a hot day, to run with the A/C on and windows up than to run with windows down (b/c of increasing car's drag).

Computer-based mpg measurements:

* 11.7/11.8 with A/C on and windows up
* 11.7/11.8 with A/C off and windows up
* 11.3 with A/C off and windows down

So, according to the computer, it's better to use A/C with windows up.

This was too quick and easy for TV, so they decided to stage a seven hour marathon, race-til-you're-empty duel, with Jamie driving an SUV with A/C on and Adam driving an SUV with windows down. Though, once the safety inspector intervened, it was no longer a seven-hour marathon, it was a bit slower (45mph instead of 55mph), and a lot shorter (only 5 gallons each).

Jamie's A/C car ran out of gas first -- Adam's windows down SUV ran for another 30 laps -- completely contradicting the computer mpg estimate. Computer estimate based on air flow into the engine, so it would appear that it is unable to properly model the difference between A/C and windows down.

Yea as i remember i thought it was that its more efficient to run with the windows down when driving slow (drag being less of a factor) and more efficient to run the A/C when travelling at highway speed.

And about the truck thingy: As some people already said it is more fuel efficient to have the tailgate up. Reasons being the stagnant air "bubble" that forms in the bed of the truck and keeps the drag low. Mythbusters aside Lockheed Martin did several tests of this for Ford mo.co. in their low speed wind tunnel so its been proven.