I've been trying to figure something out... To keep air flowing through the car, I've tried cracking the sunroof (not so it fully opens; just so the back tilts up an inch or so), and keeping the shield forward to vent the air through the smaller openings. But, it's only doing half of what I'd expected...

The rate of airflow has increased, but it seems like ambient air is still coming back in somehow? Like recently, I've had the heater cranked up (set to pull in external air), I'll crack the roof, and I start feeling cold air. Wouldn't what's coming through the heating vents keep the air flowing straight through?

 

Anyone know?

 

Not if the air leaving the car is greater than it coming in. Then you would get air coming back in through the sunroof.

 

Heat travels. Molecules move from greater energy to lesser energy. OK, that's a geeky way to say it, but you feel cooler because your hot air is leaving out of the sunroof.

 

Hmm... I figured the fast-moving air mass coming in through the vents (especially on higher fan settings) would just displace the cooler air already in the car. I first tried this with just the floor vents... Thought that would be the most effective method.

 

you're pulling air thru the vents faster than it can be heated?

 

Zoom brings up a good point, what was the temp outside? I am assuming you are pulling outside air in and not on recirc?

I bet on recirculate youd see a greater benefit, as it would gradually heat up the air and not try to cool freezing air from the outside.

 

Good point... maybe that's why. :-/ Thanks!

 

With the heater flow on high, the air should all go out the sunroof.

However, if the car is moving, all bets are off - the sunroof can move many times more air than the vents can supply, the rear tilt will suck air in thru the sunroof front at a huge rate.

The point about recirc air being warmer than outside air is a bit of a fallacy - try it yourself. We often get days when it is minus 20*, yet the air thru the vents is the same temp on "recirc" as on "outside".....I bet there isn't 2* difference when there is 50*/60* difference between temps inside and out.

S

 

^^ ?? why would outside cold air heated witih the same heating element have the same output temperature as heating interior warmer air... yes less heat will transfer to the inside air, but the internaly heated air will still be a lot hotter... now if you put a/c on with it to condition the air.. then... yah there might be little differences found..

 

in most cars, there are flapper vents that are in the back of the car, allowing any air entering the vehicle to vent out the back. also, when you just vent the sunroof, it acts the same as a cowl induction hood much like you would see on a mustang, camaro, and various other muscle cars where the air flowing over the hood, once it reaches the raised edge, gets sucked down under the hood.

 

?? why would outside cold air heated witih the same heating element have the same output temperature as heating interior warmer air

That is my point - if you do the math, it makes no sense, air source is now 50* colder, output air is very close to the same temp it was on recirc! (and no, I don't have auto climate control etc)

I was going to repeat the "try it for yourself" comment, but I see you can't, where would you get cold air in L.A.?

S

 

Hmm... Never thought about that. I just noticed that, upon opening the sunroof, the air flows out of the vents quite a bit more quickly (almost as if I'd turned up the fan another point). I figured the air coming in the vents would simply push everything out of the sunroof. Shows how much I know about aerodynamics.

 

Is the car moving? ... Just kidding. If i were you, I'll just use the AC when i'm traveling more than 60mph since you actually would save more fuel than messing up the aerodynamic of the car by opening the windows or sunroof for that matter.