Digifant CO problem

Discussion in 'Engines' started by rubjonny, Sep 9, 2005.

  1. rubjonny

    rubjonny Administrator Staff Member Admin

    Joined:
    Oct 31, 2003
    Likes Received:
    3,374
    Location:
    Bracknell
    No matter what I do I can't seem to get my digifant CO% to under 2.0-2.2. I'm using a gunsons digital CO meter.

    I've disconnected the blue temp sender, removed & plugged the breather pipe from the PCV & reved the engine to 2.5k 3 times to reset the ECU. I've tried both adjusting the allen screw & the spring inside the airflow meter to no avail, I'm setting the idle to 800rpm as specified in the Bentley.

    Can I confirm a couple of things:
    1) Do you have to plug one of the exhaust pipes as stated in the Haynes manual
    2) Is the correct value 2.0 as the gunsons manual suggests, 1.8 as I have read on here or 1.0 as specified by the Haynes and Bentley?
     
  2. KeithMac Forum Junkie

    Joined:
    Oct 27, 2003
    Likes Received:
    157
    Location:
    Kazakhstan
    I always plug the other exhaust exit when using the gunson. Depends how lean you want to run it really, I set mine for 14.7:1 afr at idle and it showed just over 1% on the MOT gastester. I think your best bet would be aiming for 1.5% co.
     
  3. TheSecondComing Forum Addict

    Joined:
    Oct 22, 2003
    Likes Received:
    47
    Location:
    Any given gutter, any given day.
    You HAVE to block the other exhaust exit when using the gunson. Leave it in position for 20 minutes while the engine warms up and set it to 2.0 in clean air.
    Then put the probe in the exhaust and see how it reads. Try it first with the AFM CO adjustment screwed right in - should give you a huge CO measurement. I normally leave the idle at 9000rpm. Then screw it right out, give it a minute to let the meter settle(make sure the pipe to the tester is claear and not blocked with water).
    If it still reads high, then tighten the AFM spring. Anything from 1-5 notches, maybe more if it's been fiddled with before.
    Ideally you want it set so that it runs about 1% when the CO screw is about halfway wound in.
    Then once all is well set the CO to about 2% at idle.
    BTW - you need to rev the engine to OVER 3k rpm 3 or 4 times after disconnecting the blue sender - I normally put it up to about 4 or 5k for a second or two each time. Otherwise your ECU will still be running in "cold start" mode, which will put your CO sky high no matter what.........
     
  4. Trev16v

    Trev16v Paid Member Paid Member

    Joined:
    Oct 22, 2003
    Likes Received:
    451
    Location:
    Oxfordshireland
    This guy is hardcore [8D]
    Edited by: Trev16v
     
    Gti1990xyz likes this.
  5. TheSecondComing Forum Addict

    Joined:
    Oct 22, 2003
    Likes Received:
    47
    Location:
    Any given gutter, any given day.
    Yeah, she revs to 18000000rpm...... [8D]
    Lol, 900rpm! Cheers trev.....
     
  6. rubjonny

    rubjonny Administrator Staff Member Admin

    Joined:
    Oct 31, 2003
    Likes Received:
    3,374
    Location:
    Bracknell
    Ah cool, sounds like I'm just not getting the ECU switched off cold running properly then, I'll try it to 4k 4 times :thumbup:
     
  7. Golden Forum Junkie

    Joined:
    Oct 22, 2003
    Likes Received:
    2
    TSC is defo correct, Haynes (why do people bother with them!) say 2.5 k, factory spec is 3 times over 3k.
     
  8. rubjonny

    rubjonny Administrator Staff Member Admin

    Joined:
    Oct 31, 2003
    Likes Received:
    3,374
    Location:
    Bracknell
    Oh yeah, what should the idle be?
    Bentley says 800 with the blue temp sensor unplugged & the breather blocked & it rises to 900 when everything is plugged back in, but that handy digifant site says 900 with everything disconnected and 800 when its plugged back in?!

    Oh yeah one more thing, I know I have to plug the throttle body end of the PCV, but should I also plug the PCV as well?

    Thanks guys :thumbup:
     
  9. Carl loader Forum Member

    Joined:
    Aug 28, 2004
    Likes Received:
    1
    Location:
    Salisbury
    You only need to plug the throttle body end of the PCV, just to stop the breather fumes from giving the wrong CO reading

    When setting the idle speed when in set up mode, you can effectively set it to whatever you want (within reason), but i normally set mine to about 950-1000rpm, which goes down to about 850 once i reconnect the blue temp sender. If i set it any lower than 950, the idle speed dips abit low when the engines cold, but part of this could be my ISV is a bit lazy

    Also, you probably have but make sure the oil temp is up to atleast 80 degrees. If its a bit cold, that will increase the CO
     
  10. rubjonny

    rubjonny Administrator Staff Member Admin

    Joined:
    Oct 31, 2003
    Likes Received:
    3,374
    Location:
    Bracknell
    Seems to have done the trick, seems a bit more responsive [:D]
    Hopefully my mpg should improve now too :)

    Cheers everyone especially TSC :thumbup:
    Edited by: rubjonny
     
  11. project_grey New Member

    Joined:
    Sep 5, 2005
    Likes Received:
    0
    Location:
    United Kingdom
    i think my motor needs abit of what youre talking about not that i realy understand.me and a friend converted a k jet 2.0ltr tweeked engine to digifant when they said it could never be done.she runs nice and drives well the cam shaft makes it run abit lumpy but im sure mines running abit rich needs setting up properly now now its running.just seems round my way people that know what you know want to charge you loads of money.is this something i could do or does it need specialist tools?if i knew what i was doing that is????
     
  12. rubjonny

    rubjonny Administrator Staff Member Admin

    Joined:
    Oct 31, 2003
    Likes Received:
    3,374
    Location:
    Bracknell
    All you need is a CO meter, a flat bladed screw driver and an allen key. The Haynes instructions are correct apart from you have to rev the engine 3 times over 3k not 2.5k or whatever it says.

    The other thing you'll probably need to do is set the ignition timing at 2k rpm :)
     
  13. rubjonny

    rubjonny Administrator Staff Member Admin

    Joined:
    Oct 31, 2003
    Likes Received:
    3,374
    Location:
    Bracknell
    Ok update, this weekend I fitted a new sump as the old one was leaking and the oil needed doing badly and also fitted a new timing belt tensioner as I noticed a rpm related squeeling.
    I had to fiddle with the engine timing and now it's a totally different car, no more digi-lag and now I can wheelspin in 1st! Woohoo! [:D]

    I assumed the idle & CO would be miles out after this so I tried to readjust, as soon as I unplugged the blue sensor the idle shot up to 1300rpm, and I couldn't get it below 1200 rpm even with the screw all the way in!
    But after I put it all back together the idle went down to 900rpm as per normal.

    The CO was at 5% but adjusting the allen screw actually worked this time so I got it to 1.8% no probs.

    Edit: I also noticed after adjusting the CO & idle this time, that now the rpm drops gradually when you dip the clutch rather than dropping quickly, which has resulted in much smoother on/off throttle in 1st, much nicer driving in traffic :)
    Edited by: rubjonny
     
  14. Carl loader Forum Member

    Joined:
    Aug 28, 2004
    Likes Received:
    1
    Location:
    Salisbury
    Alright rubjonny, don't suppose you can remember what degrees you ended up setting the timing at do you?

    Also, where did you get your gunson gas analyser from and how much was it? Im just gonna buy one and set the whole car up myself
     
  15. rubjonny

    rubjonny Administrator Staff Member Admin

    Joined:
    Oct 31, 2003
    Likes Received:
    3,374
    Location:
    Bracknell
    Got my gunson from ebay, dirt cheap 30 I think! Haven't set the ignition timing just the static, cos my timing light STILL hasn't turned up [:x]

    But on a digifant, you have to set it to 6 degrees btdc, and the ECU takes care of the advance for you. The way you do it is unplug the blue temp sensor & rev over 3k 3 times, then set it to 6deg with the engine at about 2100 rpm.

    Idealy you want a tachostrobe light so you can see the rpm whilst you're setting the timing :)
     
  16. Carl loader Forum Member

    Joined:
    Aug 28, 2004
    Likes Received:
    1
    Location:
    Salisbury
    Hello mate, that sounds cheap for a gas analyser, im keeping an eye on one on ebay at the mo (think its 60, but better than 100+ for a new one)

    I just asked about the timing cos i did have mine set to 6 degrees as it should be using my new strobe gun :) , but my engine was still pinking a bit, but this could be down to co not being quite right

    Has it taken you quite a while to get the settings just right so that your car isn't jerking on/off throttle i.e a bit of trial and error? If so, i'd much rather do all the setting up myself as i get the impressive most garages don't know how too do it properly, even though they say they do

    Cheers for the feedback :thumbup:
     
  17. KeithMac Forum Junkie

    Joined:
    Oct 27, 2003
    Likes Received:
    157
    Location:
    Kazakhstan
    They do a newer version of the Gastester Pro with a built in pump, if you could get one of these it would be a lot better to use..
     
  18. chrismc Forum Junkie

    Joined:
    Oct 22, 2003
    Likes Received:
    0
    Sounds to me like your AFM is out of adjustment or something isnt quite right if winding the idle screw right in gives you 1200rpm??

    Ideally your idle CO% of 1-2% should be achieved with the mixture (allen) screw in a mid position...

    Have you tried removing the AFM lid & tweaking the spring tension inside??
     
  19. rubjonny

    rubjonny Administrator Staff Member Admin

    Joined:
    Oct 31, 2003
    Likes Received:
    3,374
    Location:
    Bracknell
    I've now got 3 AFMs :lol:
    The original one I cracked open and fiddled with before I did all the above without much success, so I then got another one from the scrappy and fitted it in case I'd totally buggered the original. Didn't make any difference but I left it on anyway. After changing all the above I tried to adjust the CO & idle ith it but couldn't get the CO any lower than 5%.

    So then I got ANOTHER one from the scrappy which had been fitted to a 'played with' GTI, this one has been opened and resealed. This is the one currently on the car and allowed me to adjust the CO down to 1.8, this also brought the base idle down a little from 1300 to 1200 rpm.

    Would a leaking/missing idle screw make the idle go up or down, or just make it uneven btw?


    Edit: This is the gas tester I got: Digital gas tester I have the manual in PDF format in case you get one and the manual is missing like mine was :)
    Edited by: rubjonny
     
  20. rubjonny

    rubjonny Administrator Staff Member Admin

    Joined:
    Oct 31, 2003
    Likes Received:
    3,374
    Location:
    Bracknell
    Its taken 6 months of faffing to get where I am now, I've pretty much replaced & tested every part in the injection system so far, its really irritating that the whole time it was probably the timing that was out, I've checked and double checked [:x]
    Of course it could have been the oil that was too thick & gunged up causing drag, or perhaps the knackered tensioner, but I doubt it!

    Basically I turned the engien over to TDC @ piston 1 and carefully checked all the marks line up exactly, although the cambelt sproket is tricky as the Haynes & Bentley differ when describing where the mark should line up [:s]

    Edit: If its pinking under load with the timing set to 6 degrees at 2100 rpm, try using 97 RON fuel. If that doesn't help then it may be the knock sensor thats at fault, though I've never seen a definitive answer as to how you can tell if its working or not [8(]
    Edited by: rubjonny
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice