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A3 2.0TDI low poor sh*t MPG.. driving me crazy some 1help!!

Discussion in 'A3/S3/Sportback (8P Chassis)' started by AntonTDI, Oct 19, 2011.

  1. Rick @ Unicorn Motor Dev.
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    Rick @ Unicorn Motor Dev. Active Member Site Sponsor

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    Sadly the Audi engines are not as efficient as the BMW engines. quattro also results in a substantial reduction in MPG.

    The later engines are not as economical as the earlier engines. The reason is the stricter emission standards. We;ve gone from Euro3 to Euro4 to Euro5 standard engines in the last few years. We all know about DPF's - these are 100% required to meet Euro5 standards. They also increase back pressure in the exhaust which reduced the pressure across the turbine which costs power and economy.

    The other requirement is the reduction in NOX production. To achieve the highest thermal efficiency, i.e. power and economy, the diesel needs to be injected at a specific point in the engine cycle. This point generates the highest cylinder pressure and the hottest most efficient burn. Unfortunately, this point also produces more pollutants in terms of Nitrogen oxides. Later cars are calibrated with retarded ignition timing - specifically in the mid range, in order to meet emission requirements. With a careful remap you have the option of optimising this timing and bringing back your lost economy.

    Rick
    #81
  2. Beans
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    Beans Member

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    This is sad really, I thought the engine in my car was just a little more refined than my old golf. I wanted to keep away from post 2008 cars (obviously more expensive) but more costly to maintain when it's out of warranty.

    I'll look for a remap in a few months, although I'm not after total power increase - however maybe bring the power curve down a bit, but it would be nice to be more economical too!
    #82
  3. daddycool
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    daddycool New Member

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    I bought an a3 bkd for the economy as have a long commute at present & travel on average about 350 miles a week and have done 9000 miles in my a3 since mid October. And the best I've managed is 520 miles to a tank and the worse was 460 when the weather was colder, the car is A1 condition and runs perfectly. Most of the time I drive very carefully as Im spending £300 a month on fuel.

    To be honest the economy isnt very impresseive considering I was doing the same commute in my Mk2 golf gti and that was managing 450 to tank on a regular basis and that was 21 years old, petrol & didn't depreciate & have mega repair bills!
    #83
  4. daddycool
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    daddycool New Member

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    Oh & my is DIS 6 mpg out so wouldn't bother reading into that to much until you've backed it up with maths.

    I reset mine when I bought the car, it now says 48.1 for the long term average over the last 9000 miles & I've logged every fill I've made and worked it out (as im sad) & its actually doing 42.3 mpg
    #84
  5. The Governor
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    The Governor Member

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    Just to save me deciphering the manual, which reading gives you the total average on the DIS? THe one that shwos you all the info on one screen only shows a Trip Average... which is very wrong.
    #85
  6. Beans
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    Beans Member

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    The DIS shows the instant mpg, the mpg with the "o" with a cross though it shows the trip mpg (this is all in the "1" cycle). If you switch to "2" cycle it shows the same, but the mpg is since the last reset.

    Hmm, very similar to mine then.
    #86
  7. The Governor
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    The Governor Member

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    Thanks I found it. Mine says 47.7 mpg, my calculated brim to brim is actually 43.28 as I said above. So a 6 mpg over-read seems about average on these cars.

    Interestingly, my 318d was practically spot on to the calculated figures.
    #87
  8. daddycool
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    daddycool New Member

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    Mine is DSG which is offers slight condolence to myself when Im back at the petrol station!!!
    #88
  9. The Governor
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    The Governor Member

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    Another fillup today :racer: Calculated mileage 45.51 up from 43.21 last time. Each time I fill up I gain another couple of miles per gallon lol.
    #89
  10. paultaylor
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    paultaylor Member

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    I tried a fuel treatment on the last full tank and still only got 370 miles brimful to brimful.

    he worrying thing is that this tankful had a fair few of motorway trips rather than all the short heavy traffic trips of the previous tanks.

    It's a 07 2.0TDI 170 DSG sportback with 40k miles(2k miles since last full service)

    The dpf light came on once and I had to stop so I'm thinking was the regeneration stopped?

    It's done a regeneration since where I stayed on the motorway until the light went out.

    I have VCDS so I could force another regen

    has anyone any other advice as to what I could check?

    cheers
    #90
  11. max69vk
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    max69vk Member

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    Got exactly the same issue as mine with pretty much the same driving & MPG, I changed the fuel filter as it was blocked (despite only being done 3k miles previously) & the MPG is creeping back up again. I'm also looking into the torsion value (VCDS>Engine>Measuring Blocks>004 - 4th box) as after looking into this it seems that even with it being a smidge out can lose 3-4MPG.
    #91
  12. Beans
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    Beans Member

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    I just got 45.3mpg - which I think is ok. That's 510miles out of a tank (51.18litres back to brim full).
    #92
  13. Jack_tdi
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    Jack_tdi Member

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    Actually got 450I but then 420 on my next tank so slighty better but it might just be my driving changing
    #93

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