Monster MotorsportAH Fabrications
Results 1 to 15 of 15
  1. #1
    Reverse Gear

    Status
    Offline
    Join Date
    Apr 2009
    Posts
    29

    MPG worsened drastically, likely cause?

    I do a number of regular trips up and down the motorway and usually get around 38mpg rising to just over 40 on a longer trip if I'm not pushing it too hard. This has been very repeatable over the car's 2 year history with me, especially for some of the regular routes, which I do over and over. In the last couple of months that average has worsened and now I get 35mpg at best, 33mpg yesterday. The car runs without obvious issue, maybe down on power. It's just been serviced by APS and there was nothing reported.

    I'm thinking of getting it on a rolling road and having someone analyse the exhaust gases, any other suggestions as to possible causes or investigative techniques?
    B7 3.0 TDI with Bose
    After market RNS-E, Alcantara/Leather courtesy of Classic Car Services, Bluetooth, DIS

  2. # ADS
    ADS
    Join Date
    Always
    Posts
    Many
     
  3. #2
    rowdyboy's Avatar
    4th Gear

    Status
    Offline
    Join Date
    Mar 2009
    Location
    Derbyshire
    Posts
    802
    Quote Originally Posted by chrisru View Post
    I do a number of regular trips up and down the motorway and usually get around 38mpg rising to just over 40 on a longer trip if I'm not pushing it too hard. This has been very repeatable over the car's 2 year history with me, especially for some of the regular routes, which I do over and over. In the last couple of months that average has worsened and now I get 35mpg at best, 33mpg yesterday. The car runs without obvious issue, maybe down on power. It's just been serviced by APS and there was nothing reported.

    I'm thinking of getting it on a rolling road and having someone analyse the exhaust gases, any other suggestions as to possible causes or investigative techniques?
    I too have noticed similar on mine, I did a 150 mile trip and drove for economy and only got 38mpg. I have also noticed a drop in my daily commute. I serviced mine a couple of months ago. Strange!!!
    3.0 Tdi Q A4 Avant S-Line Dolphin Grey
    RNS-E retrofitted

  4. #3
    PetrolDave's Avatar
    6th Gear

    Status
    Offline
    Join Date
    Nov 2003
    Location
    U.K.
    Posts
    1,532
    Cold weather, sitting in queues,...

    In the summer I get 22mpg on my commute but in the winter I get 18mpg - all down to the engine taking longer to warm up and hence running a richer mixture for longer.
    2006 RS4 Avant (Phantom Black), RNS-E (2010 version inc SDS, HW 070, SW 0220) with AMI (250GB hard disk), Bluetooth + iPhone 5

  5. #4
    Reverse Gear

    Status
    Offline
    Join Date
    Apr 2009
    Posts
    29
    Thanks Dave, you're right there are a number of reasons why I'd get worse economy but I haven't noticed it in previous winters and that's quite a difference. Having now become a bit obsessed with this, I've tracked a couple of recent trips up to North Yorkshire, this was on the motorway almost entirely and include that chunk of the M1 around Nottingham at a very economical 50mph - still got 35 mpg.
    Any suggestions for someone in the Midlands with Audi tuning experience and a rolling road - keen to have it tested before the next MOT in case it isn't running within limits.

    Chris
    B7 3.0 TDI with Bose
    After market RNS-E, Alcantara/Leather courtesy of Classic Car Services, Bluetooth, DIS

  6. #5
    Audi A4 S-line Avant 2.0T FSI

    Status
    Offline
    Join Date
    Mar 2009
    Location
    Stevenage
    Posts
    289
    I would say it is most likely the cold weather. Sitting waiting for screens to defrost, ecu adding extra fuel for longer, heater on higher etc. I know oyuve said you didnt notice before, maybe your just more aware this time round...?
    If it's got t*ts or wheels, it's TROUBLE!

  7. #6
    Reverse Gear

    Status
    Offline
    Join Date
    Apr 2009
    Posts
    29
    Thanks TT, and sorry to hear about your car.
    B7 3.0 TDI with Bose
    After market RNS-E, Alcantara/Leather courtesy of Classic Car Services, Bluetooth, DIS

  8. #7
    Reverse Gear

    Status
    Offline
    Join Date
    Apr 2009
    Posts
    29
    I decided to check whether I had any problems, I found Monster Motorsport http://www.monstermotorsport.com/ at Loughborough who have a 4 wheel rolling road, on which you can do a run for 50. The results are below (assuming I get the tags correct) - 206PS and 474Nm which are both slightly above spec. Maybe my wife was right - I have the car equivalent of hypochondria. Anyone know what the correct Air Fuel Ratio should be for a 3.0 TDI A4 - it seems to vary from 19 to 23 from the graph.




    B7 3.0 TDI with Bose
    After market RNS-E, Alcantara/Leather courtesy of Classic Car Services, Bluetooth, DIS

  9. #8
    Neutral

    Status
    Offline
    Join Date
    Nov 2004
    Location
    Saddleworth ,England
    Posts
    79
    Diesel powered cabin heater coming on on every cold start ( providing you have your CC on Auto ) will use quite a lot of extra fuel but its worth it !
    Ian

  10. #9
    Reverse Gear

    Status
    Offline
    Join Date
    Apr 2009
    Posts
    29
    Do I have a diesel power cabin heater, I knew it was an option in Germany but didn't think it was in the UK. The car does heat up reasonably quickly but it still takes a few minutes so I suspect I haven't got one. Be interested if anyone knew how to fit one, especially at the moment.
    B7 3.0 TDI with Bose
    After market RNS-E, Alcantara/Leather courtesy of Classic Car Services, Bluetooth, DIS

  11. #10
    1st Gear

    Status
    Offline
    Join Date
    Sep 2009
    Location
    Rumburgh Suffolk
    Posts
    188
    As far as I know most of the diesels here are fitted with an electric auxillary heater that heats up the interior quicker when its cold, mine comes on if the climate is on auto and its 4.5 degrees or lower, being electric its not long before you feel warmth. The diesels being as efficient as they are naturally take longer to warm up especially when cold, running richer for longer, the alternator takes a pounding too this time of year, charging a cold battery, heaters, fans, demisters, lights.........
    when it gets milder you'll be back to normal....

  12. #11
    Neutral

    Status
    Offline
    Join Date
    Nov 2004
    Location
    Saddleworth ,England
    Posts
    79
    I thought the cabin auxiliary heater was Diesel powered ( if it was electric the current consumption would be enormous ) and made by ebac ? who can supply kits for trucks and cars , I was told that most Audis ( Tdi ) Have them .
    Ian

  13. #12
    Neutral

    Status
    Offline
    Join Date
    Nov 2004
    Location
    Saddleworth ,England
    Posts
    79
    I thought the cabin auxiliary heater was Diesel powered ( if it was electric the current consumption would be enormous ) and made by ebac ? who can supply kits for trucks and cars , I was told that most Audis ( Tdi ) Have them .
    Ian

  14. #13
    Reverse Gear

    Status
    Offline
    Join Date
    Apr 2009
    Posts
    29
    Perhaps you are thinking of Eberspacher who I think make the auxiliary pre-heater for Audi. I don't think it's an option in the UK, but it would be nice at the moment to start up a car with a warmed up engine
    B7 3.0 TDI with Bose
    After market RNS-E, Alcantara/Leather courtesy of Classic Car Services, Bluetooth, DIS

  15. #14
    On my 3rd A4! RS4 next???

    Status
    Offline
    Join Date
    Oct 2005
    Location
    Nottingham
    Posts
    159
    Hi Chris

    I have the same engine, the handbook does say that the diesel engines have a supplementary heater that runs as described above. I normally get 450 miles to a tank, this one 3/4's is gone and I've done 270!

    I put it down to the cold, queues and warming it up while scraping the windows.

    Nice result on the rolling road.

    Are you local to Nottingham?

    Chris

  16. #15
    Reverse Gear

    Status
    Offline
    Join Date
    Apr 2009
    Posts
    29
    Yes nice to see that the car isn't down on power at nearly 5 years old. I'm just south of Loughborough, near to Ashby de la Zouch - hence the wonderfully named Monster Motorsport are quite close. I did look at fitting the Kenlowe preheater, but nobody seemed confident as to where it should be plumbed into the system - you can then put it on a timer and have a ready warmed car in the morning. http://www.kenlowe.com/pre-heaters/cars/index.html
    B7 3.0 TDI with Bose
    After market RNS-E, Alcantara/Leather courtesy of Classic Car Services, Bluetooth, DIS

 

 

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Single Sign On provided by vBSSO

Garage Plus, Vendor Tools vBulletin Plugins by Drive Thru Online, Inc.

Content Relevant URLs by vBSEO