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Engine drag from AC?

Discussion in 'A3/S3/Sportback (8P Chassis)' started by Glyn E, Jul 3, 2012.

  1. Glyn E
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    Glyn E New Member

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    [Jul 3, 2012]
    A3 2.0 SE TDi 170 2008 model. Auto climate control.

    As soon as I switch on my AC unit The drag on the engine is enough to make it run roughly and appear to lack power. It certainly is nowhere near as smooth to drive with it switched on.

    It makes no difference what temperature is set, the drag is the same.

    With all other cars I have owned with AC fitted, there has been no noticeable change at all when AC is switched on.

    Is this common or normal, or do I have a fault somewhere? There are no fault codes showing.
    #1
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  3. Ash187
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    Ash187 Audi-Retrofits.co.uk Site Sponsor

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    [Jul 3, 2012]
    i think its common for a slight bit of power loss when the Ac is on, but it doesnt feel rough in mine when i switch it on
    #2
  4. mjr901
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    mjr901 S3 Pollution Plus+ Edition

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    [Jul 3, 2012]
    I seem to remember when your idle, and you switch AC on the revs dip briefly, thus changing engine note, but power wise I think it's steals something like 5-10% of yours cars power.

    its a thirsty bit of equipment!
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  5. Zak0123
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    Zak0123 Active Member

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    [Jul 3, 2012]
    Bit different but my old Peugeot 206 2004 plate used to drag slightly when AC was switched on...
    #4
  6. Johnny Bravo
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    Johnny Bravo 6+1 Gears

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    [Jul 3, 2012]
    It is normal to feel a chang in the way the engine runs when you switch on the AC but with 170 HP and at least 350NM of torque this shouldn't be THAT noticeable.
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  7. BlueTDI
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    BlueTDI New Member

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    [Jul 4, 2012]
    I have noticed this now the weather is warmer and the AC unit runs.

    Does anyone know if a AC recharge/regass will help reduce the drag?
    #6
  8. Old-Boy-Racer
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    Old-Boy-Racer Guest

    [Jul 7, 2012]
    I can barely detect any change with mine - before remap or after.
    #7
  9. Vertigo1
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    Vertigo1 Well-Known Member

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    [Jul 7, 2012]
    Never noticed this on any of my three A3s - I'd get it looked at.
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  10. RPB
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    RPB Active Member

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    [Jul 7, 2012]
    Don't notice it on my S3, but my modified Subaru was a pig to drive with it on! Changed the pedal feel big time and was noticeable.
    #9
  11. OVRA3
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    OVRA3 Well-Known Member

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    [Jul 7, 2012]
    Mine feels different with ac on really sluggish
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  12. cjsuk
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    cjsuk Member

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    [Jul 7, 2012]
    Most cars ive had with aircon on have run rough on idle, and taken power. It depends how rough and how much power loss is, and even if the aircon was really shafted I cant see how it can make more of a power loss or rougher idle.
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  13. Vertigo1
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    Vertigo1 Well-Known Member

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    [Jul 7, 2012]
    The thing I don't understand is, how do you know when the aircon is "on"?

    With climate control, whilst you can disable the aircon compressor via the ECON or AC button, if you leave it to its own devices, then it's up to the climate control system whether the compressor is needed or not. In this situation, I've not once noticed any detectable change in performance or responsiveness that would indicate whether the compressor is engaged or not.
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  14. Minstadave
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    Minstadave Member

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    [Jul 7, 2012]
    Econ turns AC off completely, atleast it does on mine.
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  15. cjsuk
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    cjsuk Member

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    [Jul 7, 2012]
    I have a bit of a noisy compressor so I know mine is on, if I leave the climate control on auto, the compressor is allways on no matter weather its its got to its temperature or not its only off when I press off or econ, so if you have it on auto all the time, you wont notice a difference as its allways on.
    #14
  16. audicruiser
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    audicruiser Audi Heaven

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    [Jul 8, 2012]
    It shouldn't be running all the time unless you have the temp set really low on a warm day... It should cut in and out.
    #15
  17. Vertigo1
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    Vertigo1 Well-Known Member

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    [Jul 8, 2012]
    I know, that's what I said. What I mean is, unless you disable it completely via the ECON or AC button, there's no way to know whether the compressor is actually on as it's up to the climate to decide and there's no indicator to tell you.
    #16
  18. 964kevin
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    964kevin Member

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    [Jul 8, 2012]
    Makes no diffeence to mine, though you can see how much fuel it takes to run on the DIS, about 1/12th gallon per hour if memory serves.

    K
    #17
  19. CornRattle
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    CornRattle Member

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    [Jul 8, 2012]
    When I turn the AC on my 2010 S3 the revs on idle pick up ever so slightly, no noticeable difference on running though
    #18

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