EM TuningChris Nott
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  1. #1
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    quattro question

    can anyone settle this discussion between me and my bro,
    he is saying the quattro system only works on the front to back not side to side, basically if you got stuck on one side the 2 wheels on that side would sit there spinning, i thought the quattros all had a locking diff, edl if i can remember? would all a4s have this or just facelift etc?
    any ideas

    cheers

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  3. #2
    "Stick a V8 in it!"

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    a lot of 4wd vehicles (including landrovers) only have 1 locking diff as standard.

    The A4 Quattro system has two open diffs in the front and rear "axle" and the centre diff is a Torsen which is basically an LSD.

    So yes, if two wheels on one side of the vehicle were to lose traction simultaneously, you'd just spin them up and go nowhere. The other issue with a torsen diff, is that if one axle loses traction completely, the torsen doesnt work, and will just shunt all power to that axle. This wouldnt normally happen on a road car unless you snapped a shaft or something.

    Early Audi Quattros (and landrovers) have a locking centre diff, meaning its either completely open, or completely locked, and this locking is controlled by a lever in the cabin. Again though, if one wheel on each axle lost traction, you'd stop.

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  4. #3
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    ok looks like i was wrong, damn i hate being wrong

  5. #4
    "Stick a V8 in it!"

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    Actually i've missed something there

    I've covered the mechanical stuff. But EDL does exist on all B5 quattros.

    EDL uses the cars BRAKES to stop the spinning wheel, and allow the open diff to transmit power to the wheel with grip. Its an electronic system, based on the ABS which is basically advanced traction control.

    So in your example, with two wheels spinning, the EDL system would activate the ABS system on those two wheels, and this would cause power to be transmitted to the other side.

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  6. #5
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    wicked, thanks for that so all b5 quattros will have EDl? near to fix my abs sensor sharpish then? im guessing it reads wheel spin for the abs sensor?

  7. #6
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    Yep, ABS needs to be operational for EDL to work, and all B5 Quattros have it.

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  8. #7
    Iceash's Avatar
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    If you were shifting a bit in first and it activates say at around 20mph for a second would you feel it vibrate the gas pedal like abs does the brake pedal?

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    no, cus the "gas" pedal has no link to the brake fluid pressure... unlike the brake pedal.

    you might be able to hear the abs pump working. the valve in the pump pulsing the brake on the spinning wheel. unlikely if your hard on the "gas"

    also series landrovers discos etc have 3 open diffs. as standard they only have a center diff lock. still rubbish in the snow! my old disco couldnt even do a dohnut in the snow!
    older more superior audis (like my 2.8 100q) have the center torsen diff and push button manually lockable rear diff, which also disables the abs.
    altho annoyingly the rear diff unlocks itself above like 16kph...... im researching what wire needs cutting/grounding to stop it knowing the vehicle speed!

  10. #9
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    so if I.m moving along quite nicely and it happens I.d feel the de acceration?

  11. #10
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    Quote Originally Posted by Iceash View Post
    so if I.m moving along quite nicely and it happens I.d feel the de acceration?
    No, EDL is not there to stop the car, it only exerts enough braking force to stop the wheel from spinning. using the brake caliper to act like the road surface, giving the wheel a resistance to turning, just like it would have if it had traction.
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  12. #11
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    what if it applies the brake as the tire regrips?

  13. #12
    jcb
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    really, All B5's have EDL?
    never seen.felt or heard mine kick in in any circumstance

  14. #13
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    all b5 quattros do.

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  15. #14
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    So if the system activates at speed surely your going to notice a brief power loss even with just having a wheel loose grip should surely affect the acceleration?

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    Quote Originally Posted by Iceash View Post
    So if the system activates at speed surely your going to notice a brief power loss even with just having a wheel loose grip should surely affect the acceleration?
    no not really.........

    these type of questions your asking sounds very much like the ones some people asked back in the 70s when people thought a system to release and reapply the brakes in the event of a wheel locking up was just stupid and wheels locked up under braking would slow the vehicle much faster. which ofcourse isnt the case.

    in answer to your question tho. no. a wheel spin interupted by the brake to enable it to gain traction will allow the car to accelarate better the same wheel allowed to just spin up beyond the vehicles road speed

    plus, unless your on gravel/snow/grass a quattro wont loose traction under acceration unles you have like 400 bhp.
    obviously in slow speed low traction conditions (snow) you'd turn the traction off so the wheels can spin to enable the car to actually make progress. in the same way as youd like to turn the abs off so you can actually stop (which you cant), except in my 100q you can!!!

  17. #16
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    So if a wheel spun on a wet man hole cover your saying i'd notice no effect?

  18. #17
    "Stick a V8 in it!"

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    You'd perhaps get a momentary loss of accelleration as the wheel spins on the manhole. But a manhole cover isnt very long, and at any sort of speed i doubt you'd notice much at all.

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  19. #18
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    well yeah youd notice in that case. the traction would be broken by the man hole cover and if your hard accelarating the wheel would probably carry on spinning up beyond it too.

    in that case the abs pump would cycle the brake on that wheel with an aim to get one sensor frequency to match the other wheels. slow it down to the speed of the other wheels bearing in mind the abs can cycle the brakes variably on and off at up to like 8 times a second.

  20. #19
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    Well that's what I wondered. There is 3 joined about 100 meters from where I normally floor it to 60 plus trucks tend to spill there fuel there as well.

  21. #20
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    Regarding B5 quattro's, I think EDL was only introduced in 1998 - but I could be wrong. My 2,8 Q Year 2000 has the latter ESP.

  22. #21
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    yeh you might be right actually.

    ETKA specifically mentions EDL from chassis code V onwards (1997) The 95/96 models dont mention EDL, so maybe they didnt get it.

    And yeh, ESP overrides EDL because the ESP does the same stuff and more.

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  23. #22
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    you wouldn't feel a drop in power as it doesn't cut the power, it just stops that wheel free spinning letting the other wheel do the work
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  24. #23
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    think its a coil pack on the way out. Done it twice week on different roads different speeds. Just gotta figure out which one as it does it for just a second?

  25. #24
    jcb
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    how do you know if you have EDL or ESP or none?

  26. #25
    "Stick a V8 in it!"

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    ESP cars have a light and a button. I believe you need ME7 for it though, so no TQS got it.

    If its post 1997 and doesnt have ESP then it will have EDL.

    2000 A4 1.8T Sport Quattro Avant, Berry Pearl
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