A\C vs Open Window

[dalkill]

Don't know if this has been discussed... if so can someone point me in the right direction.

On myth busters they did a test with exact same vehicle, drained petrol till empty, then threw in exact same amount of fuel , ran it round a track at the same constant speed, and the one with windows up and A\C on went further.

Now the other day, took the wife to the gynea, and pic up this 4x4 mag. in there some oke did a test in his disco, and it stated the window down is the more efficient option?

Who to believe?

[Scooter]

I have also seen the mythbusters episode about this.

I normally drive with the window open, mainly because the luxs AC isnt the most efficient at cooling anyway.
Now while I have never done a test myself this is my opinion:

1) With the windows down and AC off, an amount of drag is created by the wind rushing into the cab, there by causing increased consumtion, but I have never noticed any loss of power.
2) With AC on and windows up, there is a definate loss of power, up hills mainly, as well as increased fuel consumption.
3) With both AC on and windows down (defeating the purpose of an AC), you get the best of both worlds and the consumtion doesnt get any worse.

Lets face it, can the consumtion get any worse with a 4Y or 22R.

There ends my unscientific, no proof (other than feel) banter.

[ThysdJ]

It is one of those topics that actually dont have a right or wrong answer but can keep people talking for weeks... I use the aircon cos I have it, and bedamn with the rest.

If the fuel consumption gets too high because I use the aircon I lift my right foot a little...

[Dadz Toy BFI]

Deffinately better with the Windows Open

I wouldn't have it any other way





















(well I might if I had A/c )

[JohanM]

I agree with Thys on this subject. I use my aircon mainly on highways and when travelling to destinations. Around town and off road it stays off most off the time, however sometimes I do use it all the time. Fuel consumption is not to much difference when on or off on the open road, but there is a slight difference, however the less roadnoise at highway speeds do make up for the effect it has on a tank of petrol.

[CasKru]

Both is actually true and it all depends on the speed you are travelling. While in city traffic (low speed with lots of stop starts etc) it is better to have your window open and the AC of as the vehicle doesn't need to generate so much energy to get going etc. And while driving slow, wind resistance is not such a big factor. But when you have the AC on, it has to supply the energy no matter the driving conditions etc.

But when travelling at high speed (highway etc) the drag the open window causes is more than the AC pump will drawn from the engine.

So in short, low speed and city traffic... open window and highway ... AC

[Werner]

As far as I remember about that episode is that it was done around a oval track.

I see it this way:
On the oval track there are no hills like you find on an open road so there test will be correct if we had no hills.
On the raods there are hills\traffic and all other kinds of things....so according to me the conditions is not the same.

my uneducated opinion.

[BenHur]

My scientific observations lead me to the following conclusion:

If you have a good working aircon in your car and a decent HP engine that does not struggle to pull the aircon system then the fuel consumption is definitely less with the windows closed.

If your car does not have a good working aircon you will notice that now all the sudden the fuel economy gets better with the windows open

As for me, I always drive with the aircon switched on even in winter as I do not drive with the vents open as pollen and vrot diesel smoke stuffs up my sinuses. If you do not keep the aircon on, the vehicle gets real stuffy inside especially in winter with the heater running, the aircon washes the air and keep it moist.

[cprinsloo]

IIRC the Mythbuster team retested after some queries, and they came to the conclusion that above a certain speed (for a specific vehicle), the open windows create more drag than the air-con (both aircon and open windows will tap power from the engine). So in general, like Cassie sez, for lower speeds open windows without air-con is better, for higher speeds aircon with closed windows is better. I guess the best will be closed windows without aircon, but who needs that?

[Family_Dog]

Drive with A/C off? Unheard of!

Doesn't seem to make much difference for me either way, but then I seldom have the A/C switched off.


-F_D

[CasKru]

Funny enough. When I still had the Corolla I mostly drove with the AC on but now that I drive the bakkie everyday, I mostly drive with the window open.

I've got a theory why I do this but.....

[ToyX4]

Funny enough. When I still had the Corolla I mostly drove with the AC on but now that I drive the bakkie everyday, I mostly drive with the window open.

I've got a theory why I do this but.....

because yous wants to shows your smiles to everyones

[Mud Dog]

:D ..... and you want them all to see who's in the LUX

I must also wonder what has the better drag co-efficient, the Disco or the Lux. I would think the lux, cause it has better lines, less box-shaped?

[dalkill]

since I have no aircon on the lux, my choice is simple

my question is more for the rolla. Cassie, I agree with your sentiment. At lower speed in traffic out of town I have the window open. But when I reach 80km/h after that, the A\C goes on

thanks for the responses guys

[Jaws]

I have to drive with the window open so that I can keep my door closed with my elbow from the outside

I the city you have to drive with the windows close or you wil have a hunderd hawkers and beggers next to you at each robot.

Got a quote to fit a complete new aircon system the other day for R6000-00, in my opinion it is definetly worth it.

[Irishman]

All modern cars are tested in a wind tunnel to get drag to a minimum, so opening the window at any speed will increase the drag causing more fuel consumption. The modern rotary type aircons use much less power than the old compressor type, so for the price of a couple of liters of petrol you stay cool calm and collected. I have always maintained that an aircon is a safety feature. On my '91 Hilux it doesn't make a difference, as it has the aerodynamics of a brick shit house.
Ron.

[Dadz Toy BFI]

All modern cars .................................................................................... On my '91 Hilux it doesn't make a difference, as it has the aerodynamics of a brick plonker house.
Ron.