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A3 2l Tdi s-line engine flat spot

Lee_C1 Apr 28, 2012

  1. Lee_C1

    Lee_C1 New Member

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    I've just got a 2006 A3 S-Line DSG and think the car is great but have noticed there is a hesitation or flat spot when accelerating. It happens at around 4000 rpm and feels like the engine is not getting sufficient fuel, engine does continue to accelerate to the shift point still however. Any ideas or similar experiences? Thanks
     
  2. max69vk

    max69vk Active Member

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    Check your fuel filter isn't blocked, it caused me all kinds of headaches! Its located at the front driver side of the engine bay behind the headlight, you cant miss it as it has 4 pipes going to it & the top is held down by 6 torx head bolts, have a rag handy to mop up the diesel when you take the top off.
     
  3. Lee_C1

    Lee_C1 New Member

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    Thanks fuel filter would be an easy fix, wouldn't this cause issues throughout the rev range though and not just high rpm?
     
  4. max69vk

    max69vk Active Member

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    Just replied in the other thread you posted in ;)
     
  5. Craig Brake

    Craig Brake New Member

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    I Know your pain. Mine is being fully investigated by audi at the moment because of a balls up when they fitted new injectors on the recall.
     
  6. A1DEYB

    A1DEYB Well-Known Member

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    4000rpm and you're changing gear in a TDI?

    Change gear earlier, you'll hit the power band better in the next gear.

    Have you had the car scanned for faults?
     
  7. Lee_C1

    Lee_C1 New Member

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    The gear change happens after 4K rpm when in sport mode (it's a DSG) and sometimes when you kick down in standard auto mode. I'm going to take it to a Bosch dealer for diagnosis, carwoods are recommended, because I think the main dealers are expensive and often not great. The trader I bought it from gave me a warranty which so far seems to be going okay on this issue.
     
  8. Silky-S3

    Silky-S3 Is loving his new 8V S3!

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    4k+ Flatspot and TDI = Normal?

    Its a oil burner, thats how they all run init?
     
  9. mike foster

    mike foster Fossie VCDS Map User

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    Why are you going past 4k rpm with a diesel ? Power and torque hits max. long before that therefore no advantage whatsoever ! :think:
     
  10. Graham89

    Graham89 Derv Perv

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    Mine pulls hard all the way past 4k revs to 4.5k. Been mapped though. 2.0tdi 140
     
  11. Lee_C1

    Lee_C1 New Member

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    As I said I'm not changing gear, it's an auto box and the shift points are predetermined, flat spot was a bad choice of words, it's a misfire or judder. Mike, thanks for pointing out that diesel engines produce power and torque at much lower rpms, now see if you can explain why ;-) , I'll grade yr response lol
     
  12. mike foster

    mike foster Fossie VCDS Map User

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    I think you need to look at the official figures produced by whichever organisation publishes the results !

    I am not expert enough to explain why these engines produce that sort of power curve and would never presume to pontificate about it but suffice to say that the designers have incorporated much heavier flywheels to cope with the characteristics of the diesel power unit and maybe the inertial effect of the extra weight produces a much higher power to weight ratio at lower rpm , given that they need to achieve certain minimum fuel consumption figures together with particle emission regulations?

    Or not !!!!!! - just a guess :uhm: lol

    Graham, I would be interested to hear your mpg figures if you drive regularly like that and also the cost of your mapping.

    Edit : just thought - for extra points it may be that the DSG box has different gear ratios that are designed to be more efficient at higher revs !

    I've now got a headache and need to go to bed !!!!lol
     
    Last edited: Jun 7, 2012
  13. Lee_C1

    Lee_C1 New Member

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    Mike, I was just having some fun based upon your previous comment, I actually work in diesel engine development (not for Audi though) and can explain exactly why the diesel engine works as it does, thanks for contributing, I'll let you know how my issue turns out
     
  14. mike foster

    mike foster Fossie VCDS Map User

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    Lee - I was also having some fun as I haven't a bloody clue really, just guessing !!lol

    Was I anywhere near part of the reason ?
     
  15. Lee_C1

    Lee_C1 New Member

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    No problems Mike, the diesel engine uses a different thermodynamic cycle to a spark ignited engine and there are some fundamental differences. Work (and torque) is produced during a much larger portion of the engines rotation than SI and so power can be achieved at lower speeds compared to petrol. There is also a practical limitation with diesels in that there is a finite delay between fuel injection and auto-ignition (start of combustion) and the overall combustion cycle is longer because the fuel burns more slowly, this limits the rotational speed obviously. As you say the heavier components of cranks and flywheels also limits speed because of the inertias involved in their rotation.
     
  16. mike foster

    mike foster Fossie VCDS Map User

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    Got the last bit right anyway !!!lol Hope you get it sorted :beerchug:
     
  17. Old-Boy-Racer

    Old-Boy-Racer Guest

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    I might have this wrong but I believe the 2.0 TDi was designed to rev more freely and behave more like a petrol. My previous car was a Golf Anni 1.9 PD TDi - it pulled from 1200revs, was fully on song by 1500 and (before remap) ran out of puff around 3-3500revs. My A3 2.0 TDi had very little (before remap) below about 1700 but pulled well right through to 4500. Totally diiferent to drive. Not surprised that an auto box, in sport mode, is hanging on to the lower gears for so long.
     

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