An unanticipated side effect of Cd reduction

[cfg83]

evolutionmovement -

I agree with a NACA duct. I think that most race cars integrate them into side rear windows :



I think you could do it in such a way that you roll down a window to *expose* a NACA duct. Think "inner eye lid", except with a Naca duct. That's my plan, anyway.

Oooh, funaca stuff :

Driver Cooling Systems - Tech, Types, Review - Circle Track Magazine

OOC RC RACING

CarloSW2

[MetroMPG]

Interesting - I would have predicted you'd have slightly higher pressure and better flow through your windshield-base vents after lowering the stagnation point with your new front bumper (more airflow going up & over the hood.)

The hood/windshield angle hasn't changed has it? Could it be related to the windshield wiper deflector? Do they cover the vent inlets at all?

[Unheard]

Have you looked at where the cabin air exits first. If air cannot freely exit the cabin then its not going to be the most efficient system either way.

[Allch Chcar]

Originally Posted by RobertSmalls

A very interesting problem. I suspect that a wind-powered intake *ought* to be more efficient than an electric one, especially since you have a port for air to exit at the rear of the cabin. Since your alternator and blower motor are less efficient than your transmission, driveline, and tires, the latter should take less energy than the former.

Alternators are pretty efficient, the belt is already dragging so the extra drag to power the fans is relatively small.

Originally Posted by MetroMPG

Interesting - I would have predicted you'd have slightly higher pressure and better flow through your windshield-base vents after lowering the stagnation point with your new front bumper (more airflow going up & over the hood.)

The hood/windshield angle hasn't changed has it? Could it be related to the windshield wiper deflector? Do they cover the vent inlets at all?

It sounds like his air vents are the new "Vaccuum."

If you're providing a smoother path for the high pressure air, which is the goal of moving your air vent intake to a high pressure zone, then the drag should be reduced and the air pressure will be closer to ambient. With your air vent intake pulling air slower, you're probably sitting in a higher pressure zone than your intake. Changing the air vent intake should increase your airflow and reduce drag. Maintaining good airflow in your cab can reduce your drag and increase your comfort. If you're still not getting air flow use your vent fans to pull air in then use fans to increase the air pressure behind your tail. They'll pay for themselves if you use them to recycle air pressure and the better airflow, to a point of course, the better your ride will be.

[lunarhighway]

Have you looked at where the cabin air exits first. If air cannot freely exit the cabin then its not going to be the most efficient system either way.

i assume that your custom tail does not generate much "vacuum" behind the car, but still it might be worth looking for a place in the back where there's lower pressure than the cabbing an make a movable vent there. or prehaps a forward flipping spoiler like door that creates it's own suction behind it (there will be hot air sucked out of the cabin so in theory this could actially redude drag, or at least cancle the induced drag out).

other than that i'd vote for a naca duct... maybe in the roof?

[Unheard]

The aptera has the exit vents in the trailing edge i have not been able to find out where the air enters the cabin though

I have often thought under the wheel arch may be a good place for the
intake because pressure is built up there naturally. Many super cars have vents in the wheel arch just to reduce this pressure. the only issue is how clean that air would be if its wet or your driving on a dusty road.

[MetroMPG]

I think Unheard is on the mark: cabin air needs a corresponding low pressure exit, or it won't move as well.

I know basjoos recently mimicked the Aptera by adding vents through his tail to the outside. Check post #230 in his build thread for photos: http://ecomodder.com/forum/showthrea...1-0-a-290.html

I wonder where the original cabin vents were/are on the Civic...

[evolutionmovement]

Original exit vents were probably behind the rear bumper cover.

[aerohead]

basjoos,I've got the same thing going on with the T-100.I've got that blister on top of the hood and it not only shields the cowl area from direct on-coming flow,it also kicks the air over and around the windshield a bit,effectively reducing the pressure.---------------------------- My plan is to incorporate a NACA inlet at the leading edge of the blister,with a duct running between blister and hood top,to an air-tight enclosure which takes in the cowl inlet,dodging all the wiper mechanicals.----------------------------------------------- My thought is that I can harvest some of the ram-air and bring it into the cabin.Otherwise,the windows are cracked,and when the humidity goes through the roof,I've got to turn the blower on.

[basjoos]

The windshield wiper air deflector doesn't come anywhere close to covering the vent air intake area, but when I installed it, the ram air pressure took a big drop. The wiper air deflector obviously had a large effect on the smoothing out the airflow pattern and reducing the high pressure zone at the hood/windshield junction.