Air Con Sapping Power

[markyvrs]

As the weather is warming up i find that i'm now starting to use the air con quite often.

I have noticed that with the air con switched on, there is slightly more turbo lag and thus a feeling that there is less power available. I know the air con uses some of the engine's resources but is it normal for it to make a noticeable difference?

Many thanks

[Lummox]

Yeah it is only natural

[Tom_vRS]

Yep, perfectly normal.

Its even worse on the 1.2 and 1.4 engines!!!

[Decron]

Actually the real reason could be a bit more complicated than the aircon sapping power.

The aircon condenser gets hot as it is effectivly a heat exchanger. When the car is moving and when the fan is running the hot air from it and the radiator gets pushed back and round the engine bay. One of the places it ends up is the flowing round the intercooler. The less the intercooler can cool, the more lag effect and loss of power you will get.

If you do the pikey wheel arch mod you will notice that when the aircon and the car is stationary (The fan will engage pretty soon on a warm day) the hot air will spill out of the vent. I noticed this on mine after the mod which kind of proves that this is what happens and is most likely the cause of your heat soak as without the vent the hot air doesn't really go anywhere and reduces the effectiveness of the intercooler.

Doing the mod will help a lot

[Chrispy]

Isn't the A/C on the Fabia was clutchless and as such the pump is going all the time? On previous cars of mine with A/C there was a noticable thunk and drop in power when I engaged the A/C but the Fabia does not seem to do that.
As Decron says though the intercooler is in a silly place with very little in the way of air flow outwards. If the A/C fills that little space with hot air then this will surely kill performance. I'm actually thinking of doing the pikey mod myself......B&Q air vent stylee!

[ap0gee]

Originally Posted by Chrispy

Isn't the A/C on the Fabia was clutchless and as such the pump is going all the time?

It runs all the time, but at variable compression as it's a wobble plate design. More compression = more power drain, obviously...

[Chrispy]

Ahhhh I see. Always wondered how it worked.

[Mike Austin]

Originally Posted by markyvrs

I know the air con uses some of the engine's resources but is it normal for it to make a noticeable difference?

Try a long, straight and flat stretch of road; switch on cruise control; on the trip computer, select instantaneous mpg; watch the mpg change when you switch a/c on and off. The difference for me (2.0i) can be about 2-3 mpg!

[TomH]

Originally Posted by Chrispy

the intercooler is in a silly place with very little in the way of air flow outwards. If the A/C fills that little space with hot air then this will surely kill performance.

Exacerbated of course by the hot air temperature that caused you to need to switch the air con on in the first place!

[skudmissile]

Originally Posted by Chrispy

I'm actually thinking of doing the pikey mod myself......B&Q air vent stylee!

did i show you my vent chris? i anglegrindered some slits in the wheel arch liner! but now have a tt liner cut and ready to fit

[Chrispy]

Originally Posted by skudmissile

did i show you my vent chris? i anglegrindered some slits in the wheel arch liner! but now have a tt liner cut and ready to fit

Nope? Nice one mate, didn't know you'd done that....might have to take a looky.

[skudmissile]

Originally Posted by Chrispy

Nope? Nice one mate, didn't know you'd done that....might have to take a looky.

yer ill be fitting the tt arch liner after my exams, my dog bone mount came on tuesday but havent got round to fitting it yet.