Author Topic: HOW TO: Tune your Digifant GTI 8v  (Read 30718 times)

Offline rubjonny

  • 10k hero
  • *
  • Posts: 16,350
  • Location: Bracknell, Berkshire
  • Hello, my name is John and I'm a dub addict.
HOW TO: Tune your Digifant GTI 8v
« on: 25 January 2006, 09:35 »
Too many people complain about flat performance and 'digi-lag' on their 8vs.  Not many people know that this isn't actually
how the car is supposed to run, and is the result of the car not being set up properly.  After spending an afternoon setting the timing, idle & CO properly my GTI is like a rocket with instant throttle responce and blistering performance :)

First thing to do is buy a new Blue temp sender from VW, it only costs £13.  It's listed on ETKA as being for cars equipped with a catalyst, but it is the right one for your car!  Don't bother with GSF ones as they tend to fail prematurely!

Invest in an exhaust gas analyser & timing light, it will save you money and time in the long run. Plus you wont have to gamble that your local numpty mechanics know how to set up a Digifant properly!

Idle/CO:
1. Get the engine up to temp, at least 80 degrees on the MFA oil temp display
2. Turn the engine off and remove & plug the intake side of the breather pipe between the 'flying saucer' on the rocker cover & air intake
3. Hold the MFA button in and turn the ignition on, off and on again, then start the car.  This puts the MFA into a 'secret' mode.  Put the MFA switch to setting 2 and press the button till you get the digital rev counter, position 2 I think :)
4. Unplug the blue temp sender and rev the engine cleanly over 3k rpm 3 times, letting it return to idle each time.
5. Check the RPM display, adjust the idle with the idle screw on the throttle body to about 850-900 rpm. Clockwise to decrease, anticlockwise to increase
6. If you have a CO meter, block off one of the talipipes (i use a load of duck tape) and shove the probe up the pipe.  Follow the manufacturers instructions, and set the CO to about 1.8ish using the allen screw on the MAF, clockwise to increase, anticlockwise to decrease. NOTE: You must take the reading when the rad fan ISN'T running, once it cuts in it'll throw outr the reading a little!

If you don't have a CO meter, turn the screw in until the engine starts to sound rough then back it out gradually till the idle sounds smooth & even.  Check the aerial or bonnet stay for vibration, you want it smooth as possible.  This will get you close, then take it to a garage to get it set properly.
7. Reset the idle to 850-900 rpm if it has changed, and adjust the CO accordingly, repeat till you get 1.8 at 850-900 rpm :)

Timing:
1. Take out spark plug #1 and turn the engine over by hand with a spanner on the crank pulley nut until the piston reaches the top of its travel. Check by either shining a torch doen the hole or putting summat long & thin down there like a dowl rod.
2. Next check the punched hole on the inside of the camshaft sproket lines up with the head surface, with the cam cover removed.  If not slacken the tensoner and move to suit.
3. Take the dizzy cap off and make sure the rotor arm is lined up with the mark on the dizzy, which should correspond to spark plug lead #1, if not loosen the tensioner and turn the intermediate shaft.  This is a little tricky with the cambelt cover in place, though I managed to do it by removing the bolt here and bending the cover outwards.

Once you've done all that the timing should be pretty close, the next step is to set the dizzy advance.  You MUST set the timing to the factory spec, 6 deg BTDC, there is no need to set any further advance as this is done automatically by the ECU.  If you don't set it to factory spec, you'll likely REDUCE performance & MPG as the ECU cannot adjust the timing properly.

Heres a nice pic of the marks you're looking for, shamelessly stolen from the vortex, link found by the legendary 'TSC' from clubGTI  :grin:
You can see the arrow on the gearbox casing, the large notch with a bit of red paint is the 6degree BTDC mark, and the small round 'dent' to the right is the TDC timing mark.  Before you start I'd highlight both marks with tippex to make them more visible :)


1. Remove the green plastic screw in cap in the top of the gearbox, not just the little seethru cap in the middle, the hole isn't big enough to see the timing marks.
2. Get the engine up to temp, at least 80 degrees on the MFA oil temp display and turn the engine off
3. Hook up your timing light as per the manufacturers instructions
4. Start the engine again, switching on the 'secret' MFA rev counter if desired as per above, then disconnect the blue temp sender
5. Rev the engine between 2k-2.5k, and point the timing light into the hole, the 6 degree BTDC mark should now be aligned, if not loosen the dizzy clamp bolt and turn the dizzy as required
6.  Rev the engine to 2.5k again, then reconnect the blue temp sensor.  The timing should advance by about 30 degrees
7. If the timing only advances about 20 degrees, loosen the knock sensor bolt and retighten to 20 Nm (15 Ibf ft) and repeat.  If there is still no improvement, check the wiring and if this is ok replace the knock sensor.
If there is no advance at all, check the wiring to the blue temp sensor.
« Last Edit: 07 February 2007, 10:55 by rubjonny »
Hello my name is John and I'm a dub addict.

Offline Gen Martok

  • GTI forum regular
  • ***
  • Posts: 100
  • Location: Andover
  • Grab Hold Of This Girls, It's The Bannister!!
Re: HOW TO: Tune your Digifant GTI 8v
« Reply #1 on: 25 January 2006, 20:48 »
RJ, you are the BEST! My Digi is going in for its retest on Saturday, and I've asked them to tune it for me as shes running a little flat :wink: since I did the head gasket. Be interesting to see if it comes out anything like it should. Almost tempted to print this out and give it to them and say "Do it like this please!".

Stay lucky Bro! :smiley: :smiley:
91' Golf GT1 16v, 91' Corrado 16v

Offline Gen Martok

  • GTI forum regular
  • ***
  • Posts: 100
  • Location: Andover
  • Grab Hold Of This Girls, It's The Bannister!!
Re: HOW TO: Tune your Digifant GTI 8v
« Reply #2 on: 26 January 2006, 20:11 »
Bloody Pedant!!
91' Golf GT1 16v, 91' Corrado 16v

Offline FBF

  • Here all the time
  • ****
  • Posts: 355
Re: HOW TO: Tune your Digifant GTI 8v
« Reply #3 on: 02 February 2006, 00:41 »
thanks jonny im bidding on a CO meter right now