fastfrank

Hi,
Don't know if this is phycological or not but I find my scooby is more difficult to control (difficult making smooth gear changes) at slower speed whilst the aircon is ON. So much so I prefer to leave it off when possible.

Can anyone else relate to this?

F

Turbo_Steve

Certainly I have found this on most cars: The throttle seems sluggish and unresponsive in small changes, and if you nail it, the ECU seems to take a good half a second or more to switch off the aircon.
I actually find the sudden change in power output rather off putting.

fastfrank

Thanks,

How do you mean by this? Surely the aircon doesn't turn off on excelleration or am I reading you wrong?


When I nail it sometimes I've felt the car hesitate. Also backing off on pull boost and back on can be eventful . I feel the extra load it exacerbates throttle conditions.

How does the car's ECU deal with two modes of engine load? Peeps talk about doing ECU resets and driving the car afterwards to train the system for their style of driving but surley the minute you activate aircon that confuses the system???

I tend to leave aircon till I doing long Motorway stints so I don't feel it as much.


F

theotherphil

One thing that could be a factor is the poor earthing of the Subaru (only having one earthing point in the engine bay IIRC). Invest in an extra earthing kit so any voltage drops are minimised.

CataIunya

Yes the Aircon turns off under acceleration.

MaDaSS

Until i read this in the manual, it is about as believable as me turning lead into gold ffs. Sorry, but bs.
Aircon consumes power and that is that. It doesn't just turn off.
How many times on a hot day has yours turned off whilst yer using it?
Cus mine sure as f00k dont. It defintely affects the power but that is all.
Edited, just to say this is my opinion only, and in no way meant to start a flamewar CataIunya so peace

jjones

yours must be faulty then

fastfrank

i agree with madass,

So how does the system keep the air chilled then if it turns off on acceleration?

I thought the aircon compressor would be constant load on the engine till its manually turned off. I know on a hot day you can feel fluctuations in the temp but doesn't feel to me like the aircon turning off, presume there is a valve somewhere regulating temperature flow.

Sounds like false economy if it keeps switch on/off... that would make fuel economy even worse.

theotherphil,
whats IIRC?

F

MaDaSS

Yeah, whats iirc? LOL
Keep wondering that meself.

theotherphil

IIRC = If I Remember Correctly

Shows I spend too much time on the 'net

Turbo_Steve

Aircon DEFINITELY turns off when you use the throttle heavily. If you do some hard acceleration and then stop suddenly, you'll actually hear the "CLUNK" as the aircon clutch re-engages....This is why the air-con switch is wired to the ECU "Aircon_Req" line, and then the ECU controls the aircon clutch and 'additional' fan. On the legacies, if the aircon is on, it runs one of the fans all the time until you start moving above a couple of mph, then turns it off (which is a nightmare in traffic, as you can feel the 'dip' in the electrical system everytime the fan comes on).

Climate control makes all this even more complicated, as (dunno about on the scoobs, but definitely on Mazdas) it only turns the Aircon on when the cabin temperature is too high....then it turns it off again when reached....so it goes on and off all the time at idle as the temperature creeps up in the sun, and has to be brought down. This is also couple with the ECU veto'ing an Aircon request if the engine is under heavy load.

But aircon DEFINITELY switches off when you nail the throttle....thas what the hesitation is. It keeps the air chilled as the gas in pipes continues to flow regardless of the pump (for a few seconds) and indeed the chiller matrix inside the dash remains cold for a good couple of minutes without the gas flowing......remember it's cold enough for water to condense on it, so it pretty bloody cold! How long does it take a chilled pint of beer to heat up on a warm day? But the beer isn't being actively cool...it's a fairly static thermal load.

Indeed, if you KEEP the engine under load (for example driving up a long hill with a fully laden car) the aircon will usually remain on (or switch back on, making the car feel heavier) as it usually is only disabled for "throttle transients", which I would imagine is for safer overtaking. You make a sudden throttle increase...of it goes. Accelerate slowly....it stays on.

The ECU does a lot of thinking about this stuff


And it certainly ain't "BS" cos it's standard practice amongst every post 1994 car I've ever driven, and every one I've worked on.

fastfrank

Fair do's then. So where do you get all that info from?

Turbo_Steve

Experience

MaDaSS

Convinced me!
/me apologises to all if this is true.
Certainly sounds complicated enough to be! lol.

*Sonic*

Aircon also turns off when the engine is under load, ie driving up a steep incline, or towing a trailer under acceleration

The Pump has a clutch, and can therefore disengage when under load

CataIunya

I watch it turn on and off while idling....sure theres something wrong with mine....

Turbo_Steve

CataIunya, do you have climate control? It'll turn on and off all the blimmin time if you have climeate control set at fairly cool. Everytime the temp goes above the one set -=clunk=- on goes the aircon......temp reached -=click=- off it goes.......ohh look, the exhaust has warmed the cabin by 0.2degrees......-=clunk=-........cool now...-=click=-...........................hmm that sun has been shining on the windscreen for at least 30seconds....-=clunk=-.....etc etc....

I'm not knocking climate control, it just does seem to turn the aircon on and off a lot when the temps are set low. I know it's just trying to save to fuel, but I find it annoying, and invariably get the car really cold and then press the ECON or AC OFF button.

Miniman

iTrader: (2)

So let me get this right. With aircon on, your car should not feel sluggish? Or will there always be a slight pause as the aircon turns itself off.

My car feels sluggish with it on and I always have it off because of that.

scooby L

thought the air-con on subarus only turned off when full throttle (WOT) is engaged, to enable full power to the wheels (in the case of an emergency.)

All other times is stays on (normal driving conditions) and the car will feel slightly sluggish due to the additional power drain.

DBY

My WRX 03 PPP always runs and goes like a bag of spanners with the air con on, try to keep it turned off as car is so much better with it off.

regards

John

Turbo_Steve

scoobyL, it's (apparently) a function of load, rather than simply WOT.

anc-sti

I was told by a automotive engineer that aircon effecting performance on newer car is a modern day myth. At most the compressor is taking a couple of hp which isn't a great deal when you consider the large amount of horse's most scooby's have. A lot of cars also bypass the AC when the accelerator is pressed quickly, my civic type-r used to do this unsure about my sti but I can't say that I've ever noticed it effecting performance.


If you are finding that your AC is affecting acceleration get it checked out you may have a low level which is causing the compressor work harder saping more power from the engine.

Miniman

iTrader: (2)

Hmm, I'll bring it up at the next service, but the car has done this from new (still might be an issue though).

Whether its a couple of hp or not, it is noticable. I usually have it on when motorway cruising (fast road noise and open windows don't mix). If I have to pick a overtaking opportunity, I always notice the power difference.

malwrx

I have to agree with Miniman. I have an 04 WRX, (3 months old). The climate definitely effects performance more than just a couple of bhp. It is very noticeable, I actually much prefer to use the sun roof, which is shy I bought the SL model, as the fresh air must be better for you than conditioned air. I only use the air condition when (if) it is particularly hot or if I am on a fast dual carriageway. I have found this power difference to be true with my previous cars. An interesting thread, as I had not realised (or particularly noticed) that air conditioning/climate systems turned off when using heavy throttle.

Mal

Turbo_Steve

The reason it makes the car feel sluggish is because of it's resistance to turn....it's actually not so much when you push the pedal down that you notice (though the reaction is slightly less sensitive) it's more when you lift off, as the engine brakes that little harder, and so you feather the throttle that feels leaden, as the engine takes that fraction of a second quicker to react. In terms of actual power output costs, it's not hugely significant (10bhp maximum at a guess) but it's effect at lower engine speeds is more noticable because of the counter inertia on the engines spin. This is all IMO, though.