How to tune 8v gti mk2???

Discussion in 'Engines' started by 1982.rpd, Apr 17, 2007.

  1. 2dubnick Forum Junkie

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    just had a play with the AFM and took it out for a dirve, just to see if there was a difference, I think it does run a fair bit better, Iv got a 250miles drive coming up so if fuel economy is badly effected ill put it back to normal.

    All my vac pipes are newish and look A+, but I will be doing rubjonnys tunning guide this week so ill let you know how I get on with that.
     
  2. wcrado Forum Member

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    I guess the only way to tell for sure is to try this on a well set up car, wanna volunteer rubjonny??? i thought mine was running fine, but i guess it could do with checking, so hopefully get around to doing your 8v tuning guide soon, and then re-try the AFM mod!
     
    Last edited: Apr 24, 2007
  3. Phil. Forum Junkie

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    Good advise there Jonny and an excellent wtite up btw. The only reason I decided to adjust the tension in the AFM spring was the fact that I have had all the vac lines changed recently and the timing and idle setup only 2 weeks ago by a vag mechanic friend but the car still felt as though it was missing a bit in the lower revs.

    I haven't had a chance to measure mpg yet but even if it is a little thirstier it's worth it for the extra pickup below 4k. It's now very easy to spin the wheels again when taking off, something the car hasn't done for a good while.

    EDIT: Forgot to say, the main benefit though is how smoothe the car drives now. No more jerkiness when in traffic on part throttle. I can honestly say I'm delighted with the difference. (places scud on himself. Car will likely throw a leg out on the way home tonight....lol)
     
    Last edited: Apr 24, 2007
  4. 2dubnick Forum Junkie

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    i havent realy had the chance to test the difference propley as cardiff is one big traffic jam, and couldnt be bothered with a big drive but there was a noticeably difference around the 3500rpm mark were it had previously been a little dead. Im sure its not the best thing in the world for your car but its a free mod!
     
  5. StuMc

    StuMc Moderator and Regional Host - Manchester Moderator

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    I never said it was a cure -all fix!! :lol: :lol: . On my Digifant I had loads of lag low down and a flat spot towards the top end. I changed plugs, leads, vacuum pipes,everything really. Still no real improvement. I then fitted a K+N 57i and a chip that I got from Ebay (a proper one, before you say it!) Noticed a little differance, but still not totaly satisfied. My next port-of-call would have been a new AFM, but as you know they cost a fortune! So when I stumbled upon this trick I thought `why not?`. And it worked, so, I was well chuffed and as 2dubnick says a free mod.
    I agree with you rubjonny that it could be hiding an underlying AFM prob, and I did say it was fooling the ECU, but I never noticed a massive increase in consumption. The main thing is it gets you smiling again!
     
    Last edited: Apr 24, 2007
  6. 2dubnick Forum Junkie

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    Im happy, cheers for the tip! [:D]
     
  7. rubjonny

    rubjonny Administrator Staff Member Admin

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    luckily for me I found a brand new one on ebay for 50, but it still didnt solve my problems, it turnewd out to be a combination of timing and cheap crap vac lines that had perished after a month or so of use! Only buy VAG vac lines, 6 for 5 meters :)

    Edit: There are loads of other places to check, the PCV valve bung is one, and the idle screw is another. After I put my 2.0 in the idle screw would unwind itself after a week of driving :lol:

    Also if you do strip down your AFM, before you touch anything try cleaning up the contact strip with a bit of wd40 soaked paper, its just abrasive enough to take off the dirt but wont take off any of the electrical coatings (top tip from EZ_Pete!)

    Edit2: Also MK3 2.0 8v & Passat 2.0 8v AFMs are the same as MK2 ones :)
     
    Last edited: Apr 24, 2007
  8. wcrado Forum Member

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    i can't imagine that we all have faulty AFM's! yeah maybe there might be a bit of running issues with our 8v's, but you say in your tuning thread rubjonny that 8v's tend to run lean... so if thats the case then this will sort it!

    besides which, if this was causing the engine to overfuel, surely the performance would be worse not better?[:[]

    If it's improved performance at all, which on mine it has, then the engine obviously needed that extra fuel in the first place!

    i've no doubt that my engine could do with a touch of setting up, but i don't think it's so bad that i'm covering up any underlying problems.

    I've got an MOT tomorrow at 4pm, so i'll be keeping a keen eye on the co2 reading.
     
  9. rubjonny

    rubjonny Administrator Staff Member Admin

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    Exactly, AFMs don't tend to go wrong since they are sealed units, and arn't exposed to excessive heat, oil, muppet mechanics unlike some components which fail or go out of adjustment. If adjusting the AFM fixes your problems, I'm just saying don't be so sure the AFM was to blame, it could be something else thats wrong.

    In my experience digi lag is casued by several things:
    Timing, timing, timing!
    vacuum leaks
    weak fpr

    I've tuned 4 digifant cars so far with various milages, the highest miler was my own MK2 with 160k on it, ALL the engine problems were caused by one of the above problems, nothing wrong with the AFMs on any of em ;)

    The biggest problem with digifant cars is the timing, co & idle has to be setup in a very specific way, hardly any garages know or bother to check this, they just set it all up at idle and send the customer on their way. This is the leading cause of digi lag IMO, as setting the ignition timing at idle will make the car run like ar53 :)
     
  10. Phil. Forum Junkie

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    Just to add to this, my mechanic friend and I were talking about this last night. He's the guy who set my car up a few weeks ago and has build more golfs than I've had hot dinners. Just as jonny said, he reckons the best way to set up a digi is by setting the timing properly, idle and CO2 although he's interested in investigating further to see what exactly happens when you adjust the AFM.

    We're going to do a bit of investigation soon with a wide band lambda probe and see that the mix is doing throughout the rev range and hopefully tie it in with a few RR sessions to get some data.
     
  11. wcrado Forum Member

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    cool, this all sounds good!

    i'd love to get my 8v set up properly, but don't have the confidence to do it myself...... besides which my distibutor seems to be stuck in one place! i hear this is common though.

    rubjonny...you don't happen to be near cornwall do you? I'd pay you to set up my car!

    I think it's running pretty close, the idle is absolutely rock solid and where it should be. i'd like to change all the vacuum hoses though. How many in total are there? i had a good look around the engine and can only see 2 coming from the inlet, one running behind it, and one to the airbox. surely there are more than this?

    I wouldn't trust any garages around here to set up my car, i think i'd rather get them to check my cam timing and do the ignition timing myself....if i can loosen the distributor and get a timing light!

    then the only way to settle this would be to put the AFM back to normal before tuning, take it for a drive, then knock the wheel back 3 teeth again and see if it makes a difference!
     
  12. rubjonny

    rubjonny Administrator Staff Member Admin

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    Theres nothing to 'settle' tweaking the AFM can have good results on some cars, this would help an AFM with a loose air flap spring or worn contacts for example :)
    All I'm saying is you should make sure everything else is setup properly before you open the AFM and fiddle ;)

    There are very few vacuum hoses on a digi, theres a blanked off hose at the back of the throttle body, one at the front and another which runs to the AFM and the airbox with a 'T' piece. Not even 10cm worth!

    Mine would always idle ok, but it would be very hesitant and made pulling out onto roundabouts scary as it would be nothing, nothing, nothing, vrooom :lol:

    I live in Bracknell unfortunatly, so a bit of a drive. If you're ever round my way let me know and I'll try to fit you in :lol:
     
  13. StuMc

    StuMc Moderator and Regional Host - Manchester Moderator

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    God! What have I started!! [:s] :lol:
     
  14. golfpaul Forum Member

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    Did the old air flow meter operation and it worked a treat. Instant throttle response, feels a lot crisper also. Very impressed!
     
  15. rubjonny

    rubjonny Administrator Staff Member Admin

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    After the AFM mod its worth having your CO checked, in theory it should make your car run richer which might be a problem MOT time. Though the limit on MK2s is 3.5% I think, there would have to be something seriously wrong for it to be this high!
     
  16. wcrado Forum Member

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    had my MOT but decided on a pre-mot, as i knew it would fail! (bearing, cv boot etc) therefore i didn't get to hook it up to the CO2 meter.

    mot is now in 2 weeks, so i'll be checking it then!

    is it possible this 'mod' is very worthwile if a high-flow filter has been added, or shouldn't it make a difference?
     
  17. golfpaul Forum Member

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    Mines just been MOT'd so ive 11 1/2 months of fun left.
    I think the mk2 8v has a fairly high cut off anyway - should be ok.
     
  18. Mike_H Forum Addict

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    A good mod on some cars - there's no doubt. You have to be careful though, because sometimes on an old digi the AFM goes soft and opens too easily, with the result that it runs too rich, and you need to adjust to lean it out again...

    Definitely a good mod on a car that's been cammed, as it needs a bit more fuel, but as has already been said, you need to make sure everything else is right first.
     
  19. rishi Forum Member

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    how do you get to the afm (open it up?)
     
  20. StuMc

    StuMc Moderator and Regional Host - Manchester Moderator

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    Just prise the black cover off the top. It should be glued on, so you might have to gently use a screwdriver.
     

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