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Does it hurt to free wheel

Discussion in 'A3/S3 Forum (8L Chassis)' started by ads1377, Mar 22, 2012.

  1. ads1377

    ads1377 Member

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    As above really, will it hurt the haldex to free wheel down hills occasionally?

    I know your not supposed to do it as you're not in full control of the car etc

    just wondered
     
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  3. Metro

    Metro Error

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    No
     
  4. Alex C

    Alex C Well-Known Member
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    the haldex is free wheeling most of the time anyway
     
  5. Alais DJA

    Alais DJA Member

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    The haldex is completley independant until it loses traction up front which is when it wakes up....

    Essentially, like me, it's a Front wheel drive 100% of the time, until Haldex is needed where its 50/50 - therefore, doing no damage while free wheeling. :racer:
     
  6. jojo

    jojo Looking for Boost!
    Staff Member Moderator quattro Audi S3

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    As most have said, it will no effect your haldex at all.

    But I wanted to inform you that if the point of you free wheeling down the hill is to save fuel, then leave the car in gear and let it roll down with engine braking. Because the fuel injectors will switch off and use no fuel for you anyways, whilst keeping control of your car.
     
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  7. Alex C

    Alex C Well-Known Member
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    yeah, not much point free wheeling
     
  8. sportquattro

    sportquattro Active Member

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    Surely if the injectors switch off and you are using no fuel why doesn't the engine stop firing?
     
  9. Alais DJA

    Alais DJA Member

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    I was just thinking that, last time i check the A3 dosent have a stop-start engine. and would mean firing it back up everytime.
     
  10. damo.h

    damo.h DVLA Say it's Black

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    Does it still demand fuel while using the gear box to brake if you have the foot off the pedal??
     
  11. jojo

    jojo Looking for Boost!
    Staff Member Moderator quattro Audi S3

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    I wasn't aware the engine would stall if you are rolling down a hill with the car in gear!? The injectors will cut back in when the revs drop to 1200-idle speed.
     
  12. Benjiman46

    Benjiman46 R-Tech Terrorist

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    Think how a car works... Engine fires, turns the crank, which turns the gearbox, which turns the wheels.

    If you let off the loud pedal when rolling down hill BUT STILL IN GEAR, you essentially reverse this... The wheels turn, the gearbox turns and the engine turns, but doesn't fire because the injectors turn off when your engine is on what is called "over-run". The engine doesn't stall because the injectors cut back in either when you press the accelerator or when the engine speed drops to just above idle speed (about 1200 rpm) So you save loads in fuel.

    Next time you're going down hill, reset your MPG meter and it wont register anything... Because you're doing about a billion light years to the gallon ;)

    Oh and just in case you were wondering, on the over-run, the spark plugs DO still fire. It's only the injectors that cut off.

    Hope this clears up any confusion ;)

    Ben
     
  13. Benjiman46

    Benjiman46 R-Tech Terrorist

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    No
     
  14. damo.h

    damo.h DVLA Say it's Black

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    Ye I got that ;)
     
  15. Alex C

    Alex C Well-Known Member
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    its also why your instant mpg reads "---" when you are coasting down a hill....because you injectors aren't firing
     
  16. murran

    murran Active Member

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    ^^^^^ this.
     
  17. ads1377

    ads1377 Member

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    Well, I never expected this level of response. thanks a lot peeps. I've learnt allot. No more free wheeling for me!!
     
  18. A3 Oly

    A3 Oly Member

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    well thats clears up a "quirk" i thought my car had, on over run it registers ---- but when coasting it reads 200mpg

    good response
     
  19. James333

    James333 Member

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    I'm not so sure everone here is right about the original question..... A bold statement I know but in the S3 manual it says if the car is being towed, it must not exceed 30mph as it may cause damage to the 4wd system. Don't shoot the messenger mind, I have no idea why it could hurt but Audi says it does.
     
  20. 666markyboy

    666markyboy Well-Known Member

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    I don't really understant why the manual would say that either .... if that was the case then taking your foot off the gas but staying in gear at any speed abouve 30 would danage the car... there would be an awfull lot of broken S3/Quattros out there ...... i think on the A4 system you have to be carefull if the car is towed with the front wheel off the ground because thats a permanent system but that would not apply to the S3/Quattro maybe it could cook the haldex oil ?????
     
  21. Alex C

    Alex C Well-Known Member
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    i think its because if the car isnt running then the haldex pump isn't circulating the oil around the haldex clutch/diff and therefore it gets too hot when its towed? dont quote me on that though
     
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  23. aragorn

    aragorn "Stick a V8 in it!"
    Staff Member Moderator VCDS Map User

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    Not sure about the haldex cars, but real quattro cars have something similar about towing, but it specifically mentions towing with one axle off the ground, a bit like how the AA recover the car. You can tow it on a rope with all four wheels turning as much as you like, but if your towing it on a single axle lift then it has a maximum of 30miles at 30mph.
     

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