cowl/air venting
 

I want to increase the amount of vent air coming into the car at highway speeds, with the goal of avoiding air conditioning use.

Does this harm or hurt FE?

the main thing that huts fe on ac is that it has to power the compresser so since it dosent have to do this it would prolly help compaired to ac

So how about if I "REALLY" increase it.... like running a duct from the bumper through the firewall (and get it vented out the back into the low pressure area behind the car)? Help or hurt FE?

oooh now your talking! I've been wanting to figure out a way to do this as well.

I have the same problem for intake air though. In the olden days, cowel air induction worked GREAT because it was much higher pressure. Nowadays there is only a very small pocket of stagnant air there that we're trying to get at, and it's just not working for me. I had a stoopid idea of putting a little scoop on the top of my cowl reaching into the attached flow area, hopefully that would ram plenty of air into my car, and with such a small frontal area, it shouldnt' contribute to drag. Taking air from the front of the car is another interesting idea as well. The only problems i could see would be heating of the air from going over the engine.

how bout the old style vents cars used to have under the dash. They got their air from the wheel wells. There is a pretty good bit of pressure in there and would blow a lot of air into the car at speeds. It would also help reduce drag.

Yesh, i was thinking that air from the wheel wells would have been a VERY messy operation.

In some states, well Oregon at least, you are not required to have a windshield. All you have to have is the wipers!

Take that out as well as the rear glass and you have increased your airflow substantially and reduced your frontal area by a third or more!

I can see it now as the newest trend on here: Detachable front and rear glass. Imagine it, Metros topping 100 mpg.

Seriously, you know you want to try it. ;)

The idea on steroids: dramatically increase air flow from the frontal pressure zones into the interior and blow it out the back using electric duct fans, improving overall aerodynamics and adding 5, 10, 20 lbs of thrust in the process (for hella long engine off glides)

That sucks when ever you go faster than 20 mph.......

That's why god invented coroplast!

Don't forget your full face masks everyone :rolleyes:

Motorcycle helmet :D Still it was kinda cool driving without my windshield

>>Oh for Pete's sake. If that volume of air is going through the car, then the >>interior also has a coefficient of drag!

I was thinking smooth ducting all the way "through" the cab.

But further, drag is caused by redirection and surface friction... I think a volume of air can be pumped into a large space and sucked out of another location without much drag in the middle, as long as the space is large with respect to the volume of air being moved. I am not thinking 20 sq. feet times 60 mph of air though the cab... but maybe 5% or 10% of that, with the resulting drag in the cab not measurable because of the decreased velocity flow.

I am trying to think variational here... even as far back as design. Here's a few observations.

There is a lot of unused space in the car... maybe it can be use to channel air. I know you don't want a 30 mph wind in your face, but what about ducting in the doors, some on the floor corners, above the transmission... heck, the exhaust takes up quite a bit of cross sectional area, close it off and channel some bad air through there.

This whole approach could alter the aerodynamics of the car, especially if you add some energy to the flow at key points (ala vortex generator idea, but maybe active instead of passive). On the extreme engineering side, you have those synthetic jet things like on the Renault. On the simpler side, maybe catch the perimeter air right before the stream separates and channel it down through ducting into an electric ducted fan (EDF) that also provides some thrust. I am thinking hovacraft tail sucking air from through body ducting as well as the rear perimeter (to avoid separation), providing say 20 lbs of thrust with positively altered aerodynamics.

Yeah sounds crazyy I know but clearly the idea works in aircraft and already has been minaturized in the radio controlled modelling world (RC Jets... thrusting air only via electric fan... through the body of the airplane)

I've started that... a little, not in terms of improving CD though.... I guess unless one makes some really basic assumptions.... let me think on that.

But I started with the (how much energy to produce a certain amount of thrust) angle. For example:

HW750 EDF

31,100 RPM 5133.3 total watts 14.5 pnds static thrust 200MPH Efflux velocity.

https://www.gworksdesign.com/Pages/HW...motorfan3.HTML

So say 14 lbs of thrust at 5 KWh... I've got 6 Trojan T105's in the garage right now.... "I think" that is about 4.2 KWh of power (need to go through that more formally.

So the question I am wondering: A) How much longer could my engine off glides be, no change to aero, with an extra 14lbs of thrust on demand? B) How much longer with improved aero?

I think the crazy goal would be to build a system that could keep the car going steady, on level ground, no wind, etc, at say 45 mph? But I think that is on the order of a 100 lbs thrust needed, so there is a disconnect I need to close (or not if not possible). Certainly that can be closed with additional thrust but that is not practical... but push the Cd way down....???? Or effectively decrease the cross sectional area as well (a few sq feet of "direct through" ducting let's say).

Again, having fun :-)

Having fun anyway.

I improved airflow through the interior of my other car once. All I had to do was remove the weathersealing around the rear hatch. It made an obvious improvement, I could feel air flowing out of the dash vents even with the fan off. I never had to use the fan on it's highest setting. The drawbacks are increased wind noise and the possiblity of water getting into the car. I didn't have to worry about rain during a California summer.

You don't have to cut holes and fabricate ducting. Cars are already full of holes, you just need to open them up or remove some seals. Try looking behind the plastic body panels by the tail lights. On my car there's some rubber flaps that seal the tail lights to the body. These could easily be removed to vent air around the gaps in the rear of the car. There's a low pressure zone behind the car with enough suction to pull extra air through the stock vent inlets.

Be careful with this though. Depending on where the low pressure zones are at the rear, you can actually start sucking exhaust fumes into the vehicle.

On a race car I was building, I did this same thing by doing little more than lightening the lower interior surface of the rear hatch around the seal. Unfortunately it was not easily reversible and while the new venting did improve airflow, it was apparently enough to shift other stock venting into a higher pressure range that actually made them work in reverse and suck air in from a lower area behind the car - right over the exhaust by the smell of it.

Yeah, I noticed the exhaust with the hatch back open and the windows cracked. Apparently, at speed, the air pressure out the windows is lower than in the back, so I think the trick is to always vent "from" high pressure zones like the cowling and the front bumper area.

Soooo, maybe you want to suck cockpit air out of the vehicle into a low pressure, high velocity area. I am wondering if a place like the top edge of a hatch, where the air is whooshing across, would work... Maybe removing the rubber seal only on that top edge. And hope it doesn't rain...

What I am really thinking about is just to use fan power to keep the turbulent perimieter flow a little longer....aka vortex generators. Think of the airflow along the roof and sides.... streamlined at first then starting to get turbulent as it nears the back where the flow separates and causes all sorts of drag. Now imagine caching that airflow and redirecting it down and out into what would normally be the separated lower pressure area in the rear. Ideally this would be a boattail design with a single fan in the middle... where the boattail attaches to the body though is not flush but 1-2 inches separated. This should help contour the flow downward (yes a perfect boattail might do this passively as well, but now add in the flow from the high pressure areas in front of the car too). Maybe the analogy is a straw with a somewhat aerodynamic exterior... some flow simply goes through and some flows gets channeled around.... and some thrust is added as well.

It don't get crazier than this
 

Eat your heart out Basjoos

Interesting pics.
Next you should relocate the radiator just behind the fan, seal off the area between the fan and radiator, and shape the outlet duct to gradually increases in diameter.

Just for fun, anyone want to guess what this should/might do? :)

....and inject a kerosine mist and ignite

ROFLMAO!:thumbup:

That would be fun in the winter!

He may have to change the angle, looks like he may have too much down force the way it is! :D