Using the climate control fan to increase economy

[OfficeLinebacker]

Yeah, it sounds crazy, but here's my rationale:

The two areas of highest pressure on a car IRT aero are the top front edge of the hood and the cowl.

Well the cowl is where the intake for cabin air is.

If you're travelling at over 30mph and have the system on fresh air but off, you'll notice a breeze coming in. Go up in speed a bit, focus on the breeze, and crack the rear windows.

The air flow increases noticeably.

I don't know what kind of extra drag cracking a window induces, but I do know that several experimental airplanes have used air pumps to suck away the boundary layer on the wing, to great effect. The main drawback was blockage with debris.

Anyway, I have this cockamamie idea where I could somehow vent around the rear windscreen or, preferably, through the trunk, and run with the fresh air intake fan on at highway speeds?

This would have the double effect of removing air from a very high pressure area as well as helping to replace the air at the back of the car.

I plan on getting a ScanGauge soon to test instantaneous loads, but am wondering what you guys think. If any have an SG and would like to try, that would be awesome!

[Arminius]

My RPM's increase when the fan is on, so I would think there are FE issues at that level.

Interesting that Aptera uses interior airflow and exhausts it out the tip of the rear of the car to deal with turbulence issues.

[OfficeLinebacker]

Originally Posted by Arminius

My RPM's increase when the fan is on, so I would think there are FE issues at that level.

Interesting that Aptera uses interior airflow and exhausts it out the tip of the rear of the car to deal with turbulence issues.

The RPMs increase? I'd think extra load on the alternator would cause more drag in the pulley, causing the engine to slow down.

[trebuchet03]

Originally Posted by OfficeLinebacker

The RPMs increase? I'd think extra load on the alternator would cause more drag in the pulley, causing the engine to slow down.

The controller might be bumping the RPM to handle the extra load - without driveability issues

[LostCause]

I believe I read in Hucho's Automobile Aerodynamics book that someone tried ducting high pressure air from the front to the low pressure area in the rear. The overall message was that it was a lot of effort to construct such a complex duct for what amounted to a negligable/non-existant gain.

Keeping the vents open, but the fan off, will probably net you a small fraction of a percent in drag reduction. I'd be hesitant about opening the windows any, but the usual cabin air exit is under the trunk fascia behind the rear wheels. You could probably modify that duct in some way to speed up flow rates.

I bet the Aptera wake fill device is more a publicity statement expressing "aerodynamic perfection" than it serves in reducing drag. It is probably effective as a wake fill device since the Aptera's wake is so small to begin with. For that same exact reason, it is probably negligable since that small wake contributes so little to drag.

- LostCause

[Arminius]

Originally Posted by OfficeLinebacker

The RPMs increase? I'd think extra load on the alternator would cause more drag in the pulley, causing the engine to slow down.

Well, I guess my comment only applies to when I'm coasting or at a stop. I can't say for sure what it happens when I've got the transmission engaged and have my foot on the gas. Try yours at a stop and see what happens.