Right, silly question time.

I have read in various threads that air con affects performance. Surely this is only when the unit is turned on?

If the unit is turned off then performance should not be effected, right?

Thanks

Sonu

 

Correct!

 

Also correct, but if you have climate (ie WRX) if off no performance penalty, if on compressor trips in and out as required so your not entirely sure if all power there or not, but hey when you've 280ish 10hp or so doesn't make a huge difference

 

Richard, if you are lucky you may just need a top up of the gas in your system, apparantly around 15% of the gas evaporates every year in a typical car system. So after 3 years yiour are almost 50% down on effiency, if you are unlucky you have holed a pipe somewhere or something has gone PHHUTT.
Paul

 

Continuing the aircon thread... I'm sure that before my aircon was fitted I had 1 water rad fan, now I have 2. Is an extra fan fitted?

 

Nick, yes they fit an extra fan for the aircon. Under full load/throttle settings the aircon cuts out, so will give marginal performance losses, well i certainly havent noticed any

 

Ok, time for the most stupid question ever - exactly what does aircon do? I've got an STi and it has a little button for the aircon and one for air re-circulation. I kinda get what the air re-circulation thing is but what exactly does the aircon do? And what does the "Auto" setting on the fan do? Whenever I put it on Auto, the fan blows a LOT and whenever I use the aircon, there seems to be no discernible difference.

Or do I just not leave it on long enough (given that I normally get bored of waiting for an earth shattering event and turn it off after 2 or 3 minutes)?

 

Richard,

Sounds like your aircon may not be working correctly. After a fairly short time with it on, it should feel similar to sitting in a fridge . The Auto button will cause the fan to go "***** out" to start with and then slow down as the air temp comes down, then just spinning enough to keep the temp constant.

Cheers

Ken

( 94 WRX - still for sale )

 

Hmmm thanks for that guys.

Maybe I didn't make it clear enough in my original post. When I said "no discernible difference" I meant that if you have the fan on then push the aircon button there seems to be no difference. If I set the temp dial to 20 and put the fan on full, it does get rather chilly rather quickly. Having aircon on as well doesn't seem to alter it.

Mind you, the amount I spend on petrol I reckon I'd be better off leaving the aircon off anyway - can't afford the extra fuel consumption!

 

I can tell the difference with Air con on vs off, although it is not that great. Fuel econonmy suffers quite a lot.

My previous car, integra type-r suffered much more, especially up hills. The scoob has more than enough torque for it to matter less.

Anyway, isn't the use of air-con & british weather mutually exclusive?

 

What are you saying? Every day's a sunny one in an Impreza (birdies tweeting, flowers springing up etc etc)!!!

 

Richard F and others

I have an STI 5. Theres one hell of a difference with aircon on or off.

If you get in the car and just have recirc on the windows steam up badly, and you have to turn on the aircon.

Dont really know what the auto button does, also if I have aircon and recirc, don't notive a difference

Is recirc like in a normal car with no aircon.

In terms of power, I may be talking complete bollocks but there is no power difference, because you have a separate alternator to run the aircon. Does the car use both? - also told that aircon cuts out on heavy acceleartion. I've tried that and it aint true in my car, confirming what I thought - its a seperate power source.

Please inform if this is wrong!

 

The aircon compressor is run off the belts that drive the alternator but it is not electric.

There is a solenoid on the end of the compressor that allows it to be turned on and off.

When on the track it is very noticeable that the temperature in the car increases becuase of the amount of time that the car spends on full throttle but as soon as you get back into the pits it cools down.

This to me says that the car does disable the aircon when on full throttle.

Darren

 

The Aircon does indeed switch OFF under full throttle (or > a certain % )

NeilR

 

Wonder how hot it gets in the U.K. ??!

Any way even if the a/c is turned off you
are still carrying the weight of the system with you: compressor, condenser, evaporator
high & low pressure hoses , wiring harness..
....etc.

that is why the rally models are not fitted
with a/c, sun roof, stereo, sound insulation
material, alarm/immobiliser,central locking,
........etc .

When it comes to performance weight is a VERY important consideration........

 

If you follow goto

 

Richard,

Yesterday you wrote :

> Maybe I didn't make it clear enough in my
> original post. When I said "no discernible
> difference" I meant that if you have the
> fan on then push the aircon button there
> seems to be no difference. If I set the
> temp dial to 20 and put the fan on full,
> it does get rather chilly rather quickly.
> Having aircon on as well doesn't seem to
> alter it.

It sounds to me like the aircon is *always* on. If the air coming out of the vents is any colder than ambient, it must be on..... it could be that the actuator on the compressor is frozen and won't disengage... if this is the case then it's no surprise there's no difference between having the switch on and off.

FWIW, the orange LED (or bulb) in mine seems to track the compressor; when it's working, the LED is on, otherwise it's off, even if the switch is in the "on" position (lowered).

You can check out the compressor's operation quite simply; open the bonnet and have a peek at the front of the engine. There are three ancillary devices mounted at the top, all belt drive. From the left they are the power steering pump, the alternator and the AC pump.

Also... IIRC you can use the AC to dehumidify the air in your car. Pop the fan into a fixed speed setting (ie *not* auto) and wind up the temp a bit. The AC should keep running but the air temp should rise as air passes over the heater matrix... the cool AC matrix will cause most of the water vapour to condense.

You will notice a little puddle under the car after running for a while in a humid climate with the AC on. It's just the discharged water from the cooling matrix...

Hope this helps.

Cheers,

Pat.

 

The UK Impreza manual says explicitly that the Aircon system will be deactivated under "heavy engine loads". You can actually feel it in certain conditions (try nailing it in 3rd up a motorway slip road: you'll find that @ ~4k the car suddenly starts going harder!)

As for the recirculation debate: if you want to cool the car quickly and efficiently, you should use recirculation in conjunction with the air con. This way, it is cooling the air that it has already cooled, like a fridge, as opposed to having to continually cool warm outside air. The natural dehumidifying effect (mentioned in earlier posts) of the aircon cancels out the steaming up effect of the recirculation (also previously mentioned).

I have not noticed an economy decrement, but then most of my driving is either stop-start in town or *****-out in the country (in which case the aircon is off a lot of the time ).

 

Auto setting in the case of climate a/c versions means that the desired temperature is maintained by varying automatically the fan speed, compressor operation and air distribution.
A/c is becoming more useful in the UK, especially in London and other big cities during summer time.

 

The advice here in Hong Kong is that if the interior is very hot (i.e. hotter than ambient temperature), then we should first set the blower to full power with both a/c and recirc off (so that the hotter air is expelled), then turn both on after a while. This will decrease cooling time and decrease loading on the a/c system.