Motors How much power does Air Con use?

So today I took my mums focus 1.6 (2003 zetec) for a spin to the shops. And I stuck the air conditioning on as my micra doesn't have it so I thought I would enjoy the luxury.

Anyway it wasn't on especially cold or high blower speed, but it sapped so much power. I took a gap to pull out that I knew I could safely do in my 1.2 micra but it just didn't go, I had to mash my foot into the carpet to get out in time, for a few seconds I thought "sheet its not going, that cars gonna hit me" . So I am coming up to a roundabout, and flick off the AC, and do the same thing, except this time I go shooting off at the speed that a 1.6 should. The car doesn't feel underpowered at all with the AC off, its just AC on seems to make it outrageously slow, as in noticeably slower than my micra.

I didn't think that the AC was supposed to effect the power of the car that much. Is this normal, is it a case of focus + AC = suck, or does it need looking at?

 

I'm from the US and my Elantra 2L is crippled when the air is on, even with the 5 speed manual. I see 500 to 1K rpms difference at the same speed with and without. 95+ degrees F. in Denver over next 3 days and AC will be on. I will post difference in RPM since I have a "normal" route I drive each day. Starting from a standstill on a steep hill with the AC on is a different experience.
John

 

A/C does sap a major amount of power.
It also uses something like 15% more fuel though I've heard varying figures.

When I was working in South Korea, the girl I was 'friendly' with there drove a daewoo matiz 800cc.
You couldn't do hills with the air con on.
I remember a big long gradual hill between the office and my hotel and she used to leather the car for all it was worth on the way towards it to try to get as much momentum up as poss so the car would make it up with the A/C on.

Another time when we went to the other side of the island, there was heaps of really hilly roads.
We had the A/C off for about 30 mins until we got to the top of the hill and started going down.
Even without the A/C on the car had struggled, even needing to drop to 2nd gear to keep going.
Once we were going down the hill and put the A/C back on, smoke started pouring out the vents.
I **** myself thinking the car had caught fire but it was just water vapour cos it was sooo humid!

Ahh, fond memories of that trip.

 

IIRC, the average AC unit in a car takes 10-12hp off the engine. So if you have a 100hp car, it makes a big difference. If you have a 200hp car, you barely notice. At 300hp, well, it's a joke. Keep in mind that there is also a torque issue. In my old 147hp Jeep wrangler, it didn't make much difference in the AC was on or if you were towing a boat; it just went. Never faster then 120, but it went.

So, having he AC on in a 90hp super compact.....not the best for hills.

 

Um yeah... the less hp on the engine, the more noticeable I'm sure it would be. There was discussion on a car-related forum I frequent about air conditioning. The general consensus was though on hot days it was better to run the air conditioning (if it was a newer unit and the car had decent horsepower) versus having the windows rolled down... less drag with windows up versus more fuel, etc. used with air conditioning on.

 

I didn't really take into account the power:weight ratio, I just assumed that even though my micra is significantly lighter than the focus' bigger engine would make up for it.

So maths... Just so we are clear, I didn't even bother doing the maths, I used a bhp calculator

Focus AC OFF:
BHP : 98.6
KG : 1158
BHP Per Ton : 86.51

Micra:
BHP : 80
KG : 975
BHP Per Ton : 83.37

So really power to weight of my micra isn't far off anyway.
Now using Jumeira_Johnny estimate of 10-12 BHP off (I will use 10, "best case scenario")

Focus with AC on
BHP : 88.6
KG : 1158
BHP Per Ton : 77.74

Pretty obvious when you put it that way. I can defiantly tell the focus is faster, so that 3BHP(per ton) is making a difference, so the 9BHP(per ton) off with AC on really is killing it.

Well I will just have to tell my mum she needs to get herself another 10-12BHP, if she wants AC on

 

Cut a hole in the footwell and go Flintstone's style.

 

That seems extreme, what you said in your first post. 1.8 focus hardly any more powerful but I don't notice any difference in mine with AC on or off

 

Believe me it feels like such a struggle. It is exactly like you are pulling away in second or third. Once you past the initial pull off then you couldn't tell the difference as you get up to speed.

 

Can't say i've ever noticed in my 2.0 406, maybe its a torque thing.

 

more revs before clutch help at all?

 

I noticed a difference in all of my cars.
my 1.4i Polo DIED with the aircon on... it just couldn't go anywhere in a hurry... and fuel consumption would be through the roof as i would push it that much harder.
The Golf V GTI (rabbit for the americans here) could go with the AC on... and still quickly... but when i wanted to have fun, the AC would be switched off. You can FEEL the difference in pulling power. it's substantial.
my current Volvo (2005 S40 2.4i) is the car that i notice it least in, but that's probably because a) i'm not used to it just yet and b) it's a heavy car either which way you turn it, and i am used to chasing hatches around town...

 

The only thing I notice with AC on in my car is that the fuel consumption goes up, no noticeable loss of power.

 

or noise

 

my 206 1.4 HDi has barely any power difference with AC on. You can hear the revs increase by about 40 but that's it. Fuel consumption rockets though.

 

You really shouldn't notice any loss of power on a modern car. The compressor is often electrically driven (rather than from the ancillary belt). I left the aircon on when I had my 2007 Audi A6 rolling-roaded and it made 152bhp, 12 more than the book figure.

I would suggest that the Focus driver, being new to the car, was a little shy with his right foot before letting go with his left causing the car to bog down.

Edit: At any given speed in a particular gear you can't possibly be revving higher with the aircon on.... that's impossible. Aircon doesn't alter your gear ratios .

 

I would agree, but without the aircon I can drive the car perfectly fine. Also my mum has driven the car for over 2 years and she says the same thing.

As for revs, people aren't saying the aircon is making the CAR rev higher, they are the saying the loss of power due to the aircon means the DRIVER is revving higher to get going.

 

It may only be a 1.6 but it still has ~90bhp. Even if the aircon saps 10bhp it's still perfectly adequate. I've driven far slower vehicles.... Try a fully laden LWB Ford Transit. You'll never call any car slow again .

You just have to adapt to the vehicle you're in. Wait for a bigger gap or just give it more beans before you let the clutch out - doing it after will do you no good whatsoever. Zetecs need to be revved.

 

AC connects via belt to engine so saps power obviously, if your mums compressor is fooked it could add more load to the engine than normal, get someone to engage AC whilst you listen to the engine, if there is increase whine or drone you might want to get it looked at, don't know what a focus is like but if the aux belt goes due to strain from a faulty device connected to it it may be able to foul the cambelt. bye bye engine.

 

i can definetely notice the air con on in my car, its only really at low revs tho, as its kinda like nothing..nothing..nothing..turbo weeeee... so i can only imagine the non turbo version being pretty slow all the time, doesnt seem to be killing the mpg too much tho, only a drop of about 4/5 mpg in town lower than with it off.