Mod for interior airflow?

[jamesqf]

Question for the aerodynamics experts: I've been reading arguments about windows down vs A/C, and just had a thought. You have a high pressure area somewhere at the front of the car, and a low pressure area at the rear. Suppose you take some - potentially a lot more than current vents supply - air from the front, and direct it through the car. You get the same cooling effect as rolling down the windows (if not a good deal more), some "wind in your face" effect a la convertible, no frigid breeze as with A/C... and it seems you'd actually reduce overall drag.

Make sense? Or am I missing something?

[SVOboy]

There have been a few attempts at this, two which I remember well.

In one tom attempted rolling down the windows and cracking the hatch, but ultimately found that while stopped having the hatch crack allowed fumes from the exhaust to sneak in.

In the second, back when dan kroushl drove a del sol, he could crack the windows and roll down the rear window to get a similar affect.

[SVOboy]

There have been a few attempts at this, two which I remember well.

In one tom attempted rolling down the windows and cracking the hatch, but ultimately found that while stopped having the hatch crack allowed fumes from the exhaust to sneak in.

In the second, back when dan kroushl drove a del sol, he could crack the windows and roll down the rear window to get a similar affect.

[jamesqf]

I think you would want to get a little more ambitious, and use ductwork (maybe flexible insulated furnace duct, to avoid picking up engine compartment heat) to lead from the intake to interior, then more duct from the rear of the passenger compartment to the outlet, with a backflow preventer so you don't get exhaust eddies.

My Insight does have something like the exit half of this, with vents on the rear (under the plastic rear shell) that close with flapper valves.

[Frank Lee]

The ventilation system is already set up that way.

[SVOboy]

One thing I have though about doing it cutting out the bottom of the back bumper and redirecting air up into the wake.

[MechEngVT]

Both my 2002 Ram and my 1988 Ramcharger work this way. The ventilation system draws air from the high pressure area at the base of the windshield. In my Ramcharger I have a really cool vent that opens by hand and lets this high-pressure air blow up your left leg. Completely without a blower, just pushed by air pressure.

In my 2002 Ram the back of the cab has vents that allow air to escape between the cab and bed which is a low-pressure zone due to the flow separation at the rear of the roof above this gap. In my Ramcharger, the whole truck leaks so much air out the rear hatch and through the doors that the air blown in from the front is free to escape to the lower-pressure air to the sides and behind.

I really don't think this is much of a new idea. Cars without significant aerodynamic aids generate lift and therefore the air inside the cabin is at a lower pressure than the air from the front. Going back into the 30-60s vehicles with the cowl-vent open to adjustable sliding or turn-knob floor vents allowed outside air to flow in due to dynamic pressure differential. The addition of vent windows magnifies this and adds some flow to the upper body when opening the vents widely, but that really hurts your aerodynamics. The prevalence of climate-control systems in modern vehicles has replaced the need for such low-tech devices in the marketplace, making them absent even on the few vehicles that can be obtained without climate-control (are there still any?)

[wagonman76]

What Ive done for years is open the front and back (door) window the same amount. It keeps me from getting blasted, and therefore I would think it would also reduce turbulence.

[aerohead]

Originally Posted by jamesqf

Question for the aerodynamics experts: I've been reading arguments about windows down vs A/C, and just had a thought. You have a high pressure area somewhere at the front of the car, and a low pressure area at the rear. Suppose you take some - potentially a lot more than current vents supply - air from the front, and direct it through the car. You get the same cooling effect as rolling down the windows (if not a good deal more), some "wind in your face" effect a la convertible, no frigid breeze as with A/C... and it seems you'd actually reduce overall drag.

Make sense? Or am I missing something?

Germans beat you to this 70-years ago! You need to track down a copy of Baron Reinhard von Fachsenfeld's "Aerodynamiks des Kraftfahrtzeugs" ( sp? ).It's all in there.I listed the particulars for the book in my seminars and installments.Inter-library loan is a good bet.I had to drive 30 miles to a university and copy it there.Good luck!

[trikkonceptz]

In a different topic on bellypans, someone said that aluminum screening would work well as a bellypan because the air would flow over it while allowing heat to escape.

Well along those lines I was thinking of making window screen that would use the glass and window channel along with a lighweight frame to hold it all together. Hence giving me the open window I desire while pushing air over it and not in my car. Don't know if it would work, but hell, once I am done with the pan, I'll use any extra material to try it out.