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Thread: The uber digifant thread

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    AllShoNoGo Gargamelmk2 is on a distinguished road Gargamelmk2's Avatar
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    Default The uber digifant thread

    THIS IS A POST OFF OF www.generationdub.com this guy knows his MK2 stuff


    THE UBER DIGIFANT thread.



    Digifant, AKA digi, digifart, digicrap, came in many flavours in many vehicles in many forms.... we'll start with the "Bosch" generalization, to know the future, you must understand the past.....

    As most Bosch systems are referred to as Jetronic, Digifant is know in the Bosch world as an L-Jetronic Variant. Wiki defines them as such
    L meaning Luft = german for air, as opposed to CIS systems which were K-jetronic
    k meaning konstant (? kontinuous)

    Quote:
    Originally Posted by wikipedia
    L-Jetronic (1974–1989)
    Analog fuel injection. This system uses a vane-type Air Flow Meter (AFM). This type of air flow meter is called LMM, LuftMassenMesser, in all Bosch documentation. It had a much simpler and more reliable ECU than D-Jetronic, due to use of custom-designed integrated circuits. It was used heavily in 1980s-era European cars [1]. Similar systems have been built under license by Lucas, Hitachi Automotive Products, and Nippondenso. However, although their key components look similar to L-Jetronic parts, those systems should not be called L-Jetronic and parts are usually not compatible. The 'L' stands for 'Luft', which is a German word meaning air.

    LE1-Jetronic, LE2-Jetronic, LE3-Jetronic (1981–1991)
    This is a simplified and more modern variant of L-Jetronic. The ECU was much cheaper to produce due to more modern components, and was more standardised than the L-Jetronic ECUs. The connections between AFM and ECU are simplified. Three variants of LE-Jetronic exist: LE1, the initial version. LE2 (1984–), featured cold start functionality integrated in the ECU, which does not require the cold start injector and thermo time switch used by older systems. LE3 (1989–), featuring miniaturised ECU with hybrid technology, integrated into the junction box of the AFM.

    LU-Jetronic (1983–1991)
    The same as LE2-Jetronic, but with closed-loop lambda control. Initially designed for the US market.

    LH Jetronic (1982–199
    Digital fuel injection, introduced for California bound 1982 Volvo 240 models. The 'LH' stands for Luftmasse-Hitzdraht - the hotwire anemometer technology used to judge air mass into the engine. This air mass meter is called HLM2 (Hitzdraht-LuftMassenmesser 2) by Bosch. The LH-Jetronic was mostly used by Scandinavian car manufacturers and by sports and luxury cars produced in small quantities, such as Porsche 928. The most common variants are LH 2.2, which uses an Intel 8049 (MCS-4 microcontroller and usually a 4 KB program memory, and LH 2.4, which uses a Siemens 80535 microcontroller (a variant of Intel's 8051/MCS-51 architecture) and 16 or 32 KB program memory. LH-Jetronic 2.4 has adaptive lambda control, and support for a variety of advanced features including electronic boost control and fuel enrichment based on exhaust gas temperature (ex. Volvo B204GT engine). Some later (post-1995) versions contain hardware support for advanced diagnostics according to ISO 9141 (a.k.a. OBD-II). The 1995 and newer Volvo 940 vehicles are one such example.

    Now, VW has been using L-jet for years, but mk2's and corrados didn't get L-jet until late in the game... Inintally when VW had packaged this injection technoloy as digijet and was using it in the early vanagons (I believe at this point it was still bosch LE#-Jetronic) and it wasn't until about 86-89 that things start to get really ****ed up...

    now... after about 86, all watercooled vans (vanagons, transporter, etc) went to the current digifant2 system we know today. Where as the early mk2 jettas made for the california market used digifant1
    the digi1 system used on NA jettas for california market were NOT THE SAME UNITS as digi1 used on the G60 supercharged versions.

    From what I can tell, Digi1 for G60's wasn't around until about 1989, with the advent of the G60 Corrado, and then was also used in the B3 G60 Passats.

    okay.. so now.. from 80-86 we have

    digiJET = early watercooled vans
    digifant1 CALI = late style efi w/ rudimentary CEL and code storage for mk2 g/j
    digifant1 G60 = for forced induction vehicles, Passat / Corrado
    and
    digifant2 = Normally aspirated system for everywhere else in the world (except cali) used in mk2 g/j and foxes

    There were other manufactures that used similar systems, like BMW, ford, etc. (more on this later)

    And that's your history lesson for the day.

    Most people that I've encountered, usually have digi2 in a mk2 (a2) jetta or golf between 89 and 92. From what I've seen these cars typically have a hell of a time with grounds. The Ecu since it's more of a computerized system is REALLY sensitive to voltage. Various problems can stem from bad grounds from sensors not having the right voltage which gives an improper reading.... from coolant temp sensors to the O2 sensor. Typically now, the other thing with grounds and connections is corrosion. being that digifant is now getting to be about 16 years at it's newest... it may happen to have corrosion on some of the terminals. so let this be a lesson...

    CLEAN CONNECTIONS
    REMOVE CORROSION
    USE DIELECTRIC GREASE OR EQUIVALENT.....

    as far as components and sensors go... most, if not ALL digifant systems had the same sorts of sensors and outputs

    they are
    injectors (all on one injector bus)
    ISV (idle stabilizer valve)
    Oxygen sensor
    throttle switches
    knock sensor
    Coolant temp sensor
    Air flow meter
    hall sender *
    Ignition control module *

    * Debatable; these are separate component systems but required as a whole.

    now... for the most part, there's 3 main sensors that you need to be aware of.. and be aware of them in this order.

    Coolant temp sensor:
    the coolant temp sensor on most of these cars are right in the very front coolant flange, on the top, right in the very front of the head. There's two of them
    One is black, the other is blue. The BLACK one goes to the gauge in the dash... you can survive without it. the BLUE one is the one you want to pay attention to. most of the time, these go bad and the car runs riiiiiich, sometimes with a high idle.... (if it runs at all) * in a pinch you can remove the lead from the black temp sensor and plug the blue plug on the black sensor to get you where you need to go.... but replace things and run the car in proper form with the proper parts.

    O2 Sensor:
    The oxygen sensor on the digi cars are known to do all kinds of weird things... if you've got a cracked manifold, it'll run weird
    if you've got bad electrical connections / grounds..... it'll run weird......
    if things run great during open loop but shit the bed when is warmed up.... it may be the o2 not providing the right measurements.. or it's dead

    The interesting thing about most Bosch systems is that most 3 wire O2 Sensors can be made to work.
    If you KNOW you need an oxygen sensor, go to your Friendly Local Auto Parts Store (FLAPS) and ask for an oxygen sensor for a 5.0L ford 302 (came in cougars, mustangs, etc) cut off the shitty ford pigtail and solder that shit onto the proper corresponding VW harness and you're good to go! It costs 3 times less and is ALWAYS in stock.


    Air Flow Meter:
    to burst people's bubbles... digifant does NOT run a "MAF" it runs an AFM
    here's a basic explaination on how it works

    Quote:
    Originally Posted by qwikxr from the tex
    a MAF does read VOLUME of air, or MASS. The BMW, Ford and Digi2 units read FLOW.. Example.. MAF tells the ecu "Hey, Ive got 300cfm of air coming in, you need to fuel for that."
    An AFM utilizes a flapper door, that the further the "door" opens, the ouptut voltage increases. This tells the ecu that Im open "this much", so add fuel accordingly.. Since I do not have exact calibration numbers for the Digi2 AFM or the Ford/BMW AFMs handy I'll use this as an example..
    Digi2 @ idle, output equals, say, .5vdc..and the Ford/BMW units do, too..
    If the Digi unit is capable of a max flow of 200CFM and is open halfway (say, 100cfm) it puts out a voltage of, say, 3vdc, letting the ecu know it needs to fuel for 100cfm..
    Now, if the "upgrade" unit is capable of flowing 300CFM, and it, too, is open halfway (150cfm) it puts out a voltage of, say, 3vdc. The ECU sees 3vdc from the meter, and fuels for 100cfm, 50cfm short on fuel for stoich..

    and a helpful little video to fix em


    A common trick is to find a AFM / VAM from a BMW 5 series and swap it, as it has a larger bore and can flow more air. the caveat is that it needs calibration for it to work properly.. Others claim that because it flows more, that the ECU cannot fuel properly for it without a tune...... others say it works great..... so... yer on your own.. but it's a known modification to the stock vw 1.8L system

    late model vanagons and some mk2's had a wiring harness update on the AFM/VAM that corrected an issue with stalling... so if you happen to see that short piece of wire on your intake, that's what it's for.... leave it there.

    most of the time these are the sensors to watch out for mostly in that particular order




    Links

    http://www.loam.org/vw/Vanagon/Vanag...ning/DigiFant/
    http://forums.vwvortex.com/zerothread?id=1874220
    __________________

















    Last edited by Gargamelmk2; 02-13-2009 at 07:56 PM.
    Hidden Content If Nissan motorsports is called Nismo, wouldn't Honda motorsports be called Homo?

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  3. #2
    AllShoNoGo Gargamelmk2 is on a distinguished road Gargamelmk2's Avatar
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    Default Re: The uber digifant thread

    STILL MORE READING:



    This was one of the most informative tuning posts I've seen on Digi1/2





    Quote:




    Originally Posted by "digiracer" from the tex




    Who Can Play?: 87-92 Golf, GTI, Jetta, Fox, Cariolet & anything else running on Digifant II




    16 Valve Digifant II owners, this is a must do mod IMHO. Near stock or heavily moddified, 16Valve engines can really take advantage of this. Whether you know it or not, your 16 Valve has athsma & this is the cure.




    The Point: Significant increases in Horsepower & Torque throughout the entire rev range. I'll have some dyno numbers soon. If you're serious about big horsepower and you've done everything else (cam, intake, chip, exhaust) this is the next step. If you didn't catch that, this should be done last.




    Supplies Needed:




    1. Airflow Meter: (AFM) found on the 85-88 BMW 535i (most common), 635i, & 735i. It's the K Series Engine, a 3.5 Liter SOHC Inline 6.




    New AFMs for these cars are expensive, as high as $450+




    Used ones are very cheap from $40-$100 (I only paid $60, shipped to my door) & they can be found @ http://www.car-part.com/




    Search for 1987 BMW 535i under Airflow Meter




    Mine is from a 1987 BMW 535i it's a Bosch Unit.




    The part # is: 0280 203 027




    Note: Do not use the BMW AFMS found on the 325i, 328e, 525i, 528e etc. these units are the same size as our stock/OEM units. (they'll work fine, they just won't give you anymore power)




    Note: Your engine is not going to pull the vacuum of a 3.5 liter 6cyl. Therefor you need to reduce the spring tension to allow your engine to idle properly. (with my 2.0L ABA/1.8 head I found reducing tension 8 clicks to work best) If you're using a 1.8L I assume you'd need to reduce it more.




    Their's no wire splicing or cutting involved, it's a straight plug & play deal, it connects using your Factory Connector.





    2. 3 Inch Intake Piping: cut to desired length, I purchased mine @ Summit Racing Equipment & paid too much.




    You'll need atleast 2 feet & 3-4 hose clamps.




    AT Sears Hardware, I found 3inch Clothes Dryer Ducting in 2 foot sections for only $4.99 a section & it looks identical to the fancy Summit Racing Tubing I spent $60 on.




    Sears also has quick release 4" clamps for only $1.09 a piece.





    3. 3Inch K&N, ITG Racing Filter or other similar style cone air filter. Again I probably paid too much, I bought my K&N @ Summit Racing for $36.





    4. Larger Fuel Pressure Regulator (FPR) depending on your mods, Cam & how well the head flows you'll need atleast a 3.5 bar to a 4.5 bar FPR. The 3.5 bar is a stock Porsche 944S Unit & can be found @ http://www.germanautoparts.com/ for $41.




    The part #s for the 3.5 bar FPR is:




    Bosch part# 0 280 160 263




    Porsche part # 944 110 198 03





    'd suggest a 4bar FPR or better yet an adjustable FPR.




    Find out more about them in my 4bar/ Adjustable FPR Thread









    To go larger you can crush a stock one yourself using DIY instructions @ http://www.snstuning.com/DIY/FPR/fpr.htm





    Ideally you'd want an adjustable FPR & a air/fuel ratio meter to tune it with but again not required.




    This is the Adjustable/Rising Rate FPR I'm using:








    It's a Malpassi FPR from Bavarian Autosport for BMWs.




    It's an excellent unit but fits very tight & is not recomended for use with a G60 Valve Cover or other boxed valve covers.






    Depending on how far you go, you'll need bigger injectors.




    I'm using these: 24 lb Accels I noticed a nice improvement in throttle response with these. Alot of the 16 valve Digi2 guys are using stock 24-26 lb G60 Injectors.





    5. A better chip is suggested but not required.




    AMS is by far the best chip currently available.








    Increases injector pulse width(more fuel), has agressive timing maps, & raises the rev limit to 7,000 rpm. (with the right mods, you'll make power that high with this AFM)




    A cheap alternative is the SNS Cam Chip, it only increases fuel but you'll still have the stock 6,200 rpm rev limit & it does nothing for timing. It's only $39 & better than nothing.









    BMW AFM vs VW AFM Size comparison:





    The Door measurements:




    VW AFM 2" H x 2 1/16"th W /50mm H x 52mm W




    BMW AFM 2 9/16"th H x 2" W /65mm H x 50mm W




    Inlet Sizes:




    See Door Measurement for VW AFM




    BMW AFM 3" or 75mm in Diameter




    Outlet Sizes:




    VW AFM 2 9/16"th or 65mm in Diameter




    BMW AFM 3" or 75mm in Diameter





    This is the Inlet Ring that comes with the BMW AFM, so you don't have to deal with using round hose on a square hole.






    Chiptuning is also now quite standardized for digifant systems... there's various companies out there that have developed chips.








    -VWPilot / Digifast ?








    -others?






    There is a condition with both digi1 and digi2 systems commonly called "digilag"





    digilag is the lag between going WOT and having to wait for fueling to "catch up" this has been fixed with most chiptuning software....












    some more links
























    __________________




    Quote:
    Hidden Content If Nissan motorsports is called Nismo, wouldn't Honda motorsports be called Homo?

  4. #3

    Default Re: The uber digifant thread

    lol
    nice to see my post making it on here too.....

    thanks Julian


    oh ya.. dont forget my uber CIS thread too

    http://forums.generationdub.com/showthread.php?t=21624
    Last edited by BellCityDubber; 02-05-2009 at 08:42 PM.

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  6. #4
    AllShoNoGo Gargamelmk2 is on a distinguished road Gargamelmk2's Avatar
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    Default Re: The uber digifant thread

    *Props* to Bellcitydubber....I was so impressed I had to share...
    Hidden Content If Nissan motorsports is called Nismo, wouldn't Honda motorsports be called Homo?

  7. #5

    Default Re: The uber digifant thread

    it gets better... I could go on for hours about what they changed on the mk2 over the years...

  8. #6
    Pancake spencerem is on a distinguished road spencerem's Avatar
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    Default Re: The uber digifant thread

    Holy shizznit. Read that twice, very very nice. kudos on info

  9. #7
    not your typical air ride DasBohan is on a distinguished road DasBohan's Avatar
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    Default Re: The uber digifant thread

    jesus. I attempted on multiple occations to understand this. First i thought i was late night cracked out, then i just realized i was a mkiv retard.
    Hidden Content Originally Posted by Boost Addicted Hidden Content
    All girlfriends are legal. Its just what you do with them that may be questionable lol
    Hidden Content Originally Posted by OregonDweller Hidden Content
    he just wants all your scene points Ryan, careful.

  10. #8

    Default Re: The uber digifant thread

    If any body still facing this problem then contact me... I hope that i will provide a good solution....
    MALAKI

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    Default Re: The uber digifant thread

    im having some issues with my mk2. i have a digi sohc 1.8l, well the issue is when i start it, the rpm goes up and down over and over. now if i turn my a/c or heat on, the rpm jumps up to about 2-3 grand and idles up there. im also having an issue with the fuel pump relay. sometimes the car wont start and i need to push/wiggle the relay to get the pump to go. i was cruising one time and the motor cut out on me, thank god i was in 5th gear, i pushed on the relay till it turned over and only had to drop down to 4th gear.

    i love my car and wouldnt get rid of it for anything.i just want to finally have all the kinks out before i start aiming for more power.

  12. #10
    Euro Snob Vixen is on a distinguished road Vixen's Avatar
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    Default Re: The uber digifant thread

    Why is this not a sticky? I fail D:
    IMD | IG @VixenVR6 | sLoww MK4 VR6 RIP | MK6 2.5 SEL

  13. #11

    Default Re: The uber digifant thread

    lol
    I'm glad to hear all the positive response on the thread!
    I've had all kinds of issues with Digifant... and I'm currently learning how to re-write the chips in these.

    Necrobynx: You either have a massive vacuum leak, or your ISV is fubar'ed... that's why your idle is going all wonkey...

    and try to replace the relay, but while you have it out.... drop the fusebox and check for corrosion. mk2's tend to leak over the fusebox from the windshield.... if you had the windshield replace it may have not been sealed properly.. or if it's rusty, it could leak.

  14. #12
    AllShoNoGo Gargamelmk2 is on a distinguished road Gargamelmk2's Avatar
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    Default Re: The uber digifant thread

    Damm Phil your a ghost...realize your post was a month ago but havent heard tell of you in ages..been on gendub here and there but too much new style talk for me..PM me if you read this in the next year or so..lol..
    BTW I still refer to this thread all the time..its why its also in my sig all mk2 owners should treat this as a second bible to the bentley..
    Hidden Content If Nissan motorsports is called Nismo, wouldn't Honda motorsports be called Homo?

  15. #13

    Default Re: The uber digifant thread

    I figure I'd pop my head in here and say what's up...
    Thanks to Gargamelmk2 for posting my info far and wide

    there's a new UBER guide in the works that I may post up when I get time to sit down and rack my brains

    There will be an Uber digifant 1 (g60) Thread in the future, when I'm done the new project.

    you heard it here first Jetta Junkies....

  16. #14
    Euro Snob Vixen is on a distinguished road Vixen's Avatar
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    Default Re: The uber digifant thread

    Quote Originally Posted by BellCityDubber View Post
    I figure I'd pop my head in here and say what's up...
    Thanks to Gargamelmk2 for posting my info far and wide

    there's a new UBER guide in the works that I may post up when I get time to sit down and rack my brains

    There will be an Uber digifant 1 (g60) Thread in the future, when I'm done the new project.

    you heard it here first Jetta Junkies....
    Awesome. Shoot me a PM with a link to the new threads once you get 'em done!
    IMD | IG @VixenVR6 | sLoww MK4 VR6 RIP | MK6 2.5 SEL

  17. #15
    Junior Member Wrenchy is on a distinguished road Wrenchy's Avatar
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    Default Re: The uber digifant thread

    Hi Great thread
    but can anyone point me to a site thread etc on the MK2 Diesel-
    I have an old 91 and am new to diesels- love the car-
    havent had so much fun since DKW days lol

  18. #16
    AllShoNoGo Gargamelmk2 is on a distinguished road Gargamelmk2's Avatar
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    Default Re: The uber digifant thread

    Not much on here relating to mk2 diesels unfortunately
    Fourtitude.com is a good forum tho
    Hidden Content If Nissan motorsports is called Nismo, wouldn't Honda motorsports be called Homo?

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    Junior Member Wrenchy is on a distinguished road Wrenchy's Avatar
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    Default Re: The uber digifant thread

    Quote Originally Posted by Gargamelmk2 View Post
    Not much on here relating to mk2 diesels unfortunately
    Fourtitude.com is a good forum tho
    thnx but that seems more of a 'worship site lol
    Last edited by Wrenchy; 05-28-2012 at 07:51 AM. Reason: x

  20. #18

    Default Re: The uber digifant thread

    heh... I always manage to provide to this thread... in some shape or form.
    digi1 and digi2 threads are still being made.

    for IDI TD info, go to vwdiesel.net

  21. #19
    AllShoNoGo Gargamelmk2 is on a distinguished road Gargamelmk2's Avatar
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    Default Re: The uber digifant thread

    Phil you old lurker you...tried to send you some msgs on GenDub but my account was locked. I was down your way a few months back a buddy of mine picked up a rabbit in Toronto.
    Hidden Content If Nissan motorsports is called Nismo, wouldn't Honda motorsports be called Homo?

  22. #20

    Default Re: The uber digifant thread

    heh... yeah.. Gendub doesn't like me anymore...

    had lots to do with this build, very interesting if you're a technical minded person

    http://forums.vwvortex.com/showthrea...-So-here-we-go....

    And those who knew a bit of something said it wouldn't work.... well, it works fan-fuckin-tastic


    I always do my thing on the tex.... despite if people are watching or not.... listening or not.... building or not..... I'm always doing my own thing there.

    next time you're down this far... pm me on the tex...

    I've been hella busy with trying to get the corrado back on the road... I swear I'll get back to an uber Digifant thread when I can....

  23. #21
    AllShoNoGo Gargamelmk2 is on a distinguished road Gargamelmk2's Avatar
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    Default Re: The uber digifant thread

    right here is why I always liked you man
    "I always do my thing on the tex.... despite if people are watching or not.... listening or not.... building or not..... I'm always doing my own thing there"

    Awesome build thread Phil...everyone rockin Rados makes me miss mine more
    I'm in the middle of a G60T "mess" in the ol' Jetta...
    Hidden Content If Nissan motorsports is called Nismo, wouldn't Honda motorsports be called Homo?

  24. #22

    Default Re: The uber digifant thread

    I see a description about the black and blue sensors in the flange but I have a white
    sensor also in the smaller flange on the end of the block going to the heater core hose. I just noticed it has no plug anywhere that I can see in my engine bay and is just doing nothing. What is the purpose of the sensor in the digifant system and does anything act quirky if it is not connected?

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  25. #23
    AllShoNoGo Gargamelmk2 is on a distinguished road Gargamelmk2's Avatar
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    Default Re: The uber digifant thread

    what years the car? I'm on my phone and can't quite focus in on your pic
    Hidden Content If Nissan motorsports is called Nismo, wouldn't Honda motorsports be called Homo?

  26. #24

    Default Re: The uber digifant thread

    Latter 1989, early 1990. 1989 for all intents and purposes. There are two wires going to a bolt on the flange (u can see in the pic) that I assumed to be some type of ground. Would those possibly be the leads? VIN is WVWRB11G2KW....

  27. #25

    Default Re: The uber digifant thread

    That sensor isn't involved in any engine management and has nothing to do with digifant (or cis, etc)

    that sensor, IIRC is for AC fan control... your car had AC at one point eh?

  28. #26

    Default Re: The uber digifant thread

    It has functioning AC right now. I don't see a plug anywhere to this sensor though. I do see two wires going to a bolt on that flange and wondered if they were the wires that are supposed to go to the sensor plug if that plug existed in my car - see that pic I included. this is what I see online about that sensor.


    Water Temp. Sensor

    A/C Cut-Off
    With Digifant
    (119c 2 Pin, Grey/White) Mounted in water flange at cylinder head.

  29. #27
    AllShoNoGo Gargamelmk2 is on a distinguished road Gargamelmk2's Avatar
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    Default Re: The uber digifant thread

    Quote Originally Posted by BellCityDubber View Post
    eh?
    How very Ontario of you Phil..lol
    Hidden Content If Nissan motorsports is called Nismo, wouldn't Honda motorsports be called Homo?

  30. #28

    Default Re: The uber digifant thread

    the car has working ac. This sensor has always been there but there's no plug to it and I can't tell where any wires that go the sensor might be located. The fan is ALWAYS on and on high when the AC is on.With the ac off it functions sporadically on and off within seconds, on too long after the car is turned off...Thanks guys

  31. #29
    Digifook. CafeRacer is on a distinguished road CafeRacer's Avatar
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    Default Re: The uber digifant thread

    I thought I would chime in some Digifant advice that I didnt read much up on yet in this post or in any other online sorce. Im in no way Hi jacking, just contributing good info and advice. In particular this applies to the Digi2 in Mk2 cars. The Digi system on the Audi 5 cylinder engine, also used in Euro Vans is the same principal but the wire points differ.

    Grounding: Its the major cause of any issues, easily fixed and maintained in these cars. Everyone is told to check the grounds but half of them are easily overlooked and only the less crucial ones are fixed.

    Ground points under the hood:
    Brown/black two wires into one connector - Valve cover stud or coolant flange - fuel injectors.
    Brown/white two wires into one connector - Valve cover stud - sensor grounds.
    Bare wire braid/sometimes covered coming out of O2 sens harness - valve cover stud - O2 sens sheilding ground.
    Flat strap covered in plastic - valve cover stud - body ground for cowel and roof.
    Thick bare wire OEM - bell housing to post behind battery to battary negative - main engine / starter ground, body ground.
    x2 seperate Brown - harness to battery negative - one is ECU ground, one is Ignition Modual ground.
    Thick brown - Fuse block ground. Z2 connection on block to battery.

    As much as its important to have clean ground connections the ones on the engine itself are very low current. Excessive dirt or corrosion will impede them and the engine managment will suffer from that. The biggest and most common ground issue is the main engine ground. The bell housing connection is the one that stays the cleanest since it is very large but alot of these cars by now have had the origional battery cable end replaced with the cheap style that sandwitches the wire/wires with 2 bolts. These are higher resistance to begin with and also get corroded really quick due to the nature of batterys venting. The alloy is also very soft to allow it to fit snug to a varity of post sizes. You will find they loosen off and stretch out really fast. If you have to use a clamp like that crimp on a battary cable ring connector and seal it with heat shrink of according color for ID. Then bolt that to the cheap connector. Unless its been replaced recently any OE battery cables should be repalced. Positive or negative.

    The ECU and ignition module ground are direct to the battery as they have a higher draw of power and need the best possible ground. You can ground them to the body, or engine but you will feel that wire get really warm, really quick. Because they come out of the harness at the battery its virtually impossible to mis place them.

    The Sensor and injection grounds will work just fine at the valve cover stud, or on the coolant flange stud.

    A very big mis conception is that the flat strap going to the valve cover is the ECU or Coil ground. It mearly shares a bolt from the coil bracket and is only a static ground.

    Adding redundant grounds:
    Its often advised to add a redundant ground that bridges the sensor grounds to the bell housing or the battery itself. On my own car I tested the theroy and noted no change at all. Before removing it I tested the resistance between the according ground on the main engine harness at the ECU and the battery. All the engine mounted grounds outside the bell housing to battary ground had higher resistance than if just left stock. I later tested this again with 2 friends cars with typical Digi issues that ended up being partly grounding and partly other reasons.

    The only worthwile addition or change to the grounding is with the main engine ground itself. From factory it ties in to the post behind the battery and then to the Battery itself. This works just fine on a bone stock car. A well paid team of engineers came up with it, tested it and said it would work. If you have had to replace the entire cable at one point and a factory one wasnt used that crucial body ground is left open. If you have swapped to a Quad round light set up where the relays, and 4 bulbs are now grounding into the battery you will require it and even the stock one is now not quite up to par. In most cases having two thick cables, one from the bell housing and one from that post works really well. Headlights are usually brighter for it, somthing I noticed even in my own car. Its also a good idea to go with this method if you have added an amp and sub box to the car and grounded it to the body somwear.

    Dialectic paste:
    VW recomended using stabilant on all connections under the hood. This was mainly because non of the connectors at the time were well sealed compared to modern cars. There is also no noticeable resistance differance if you coat the threads or connections prior to install. If you used a paste other than stabilant on the threads or connections you can actually add more resistance, particularly in a low power ground or connection. If you have clean connections putting a thin layer of any dialectic paste or even anti sieze over top to help sheild it works just as well and is far less messy.

    Cleaning all the ground, espessialy the battery itself - positive and negative - is almost allways been done the lazy way. Simply blasting it with brake clean and wiping it off after wont do. It should be phisically taken apart, lightly sanded clean, then sprayed and wiped. Frequancy will depend on climate to some degree but even in the wettest places on earth once a year is plenty. Frequancy is also effected by the cleanliness and maintance of the engine itself. IE if your valve cover gasket is not doing its job you will have to clean the grounds in that area more often. To clean the main connector at the ECU and Ignition module simply remove, spray with contact cleaner and re install it. They are typically well sealed.

    Since most ground issues originate at the battery cables themselves finding a battery bag is one of the easiest ways to keep things clean. Another cheap and productive measure with any car is to replace all the ring connectors with equally good quality ones. Crimp them on the way they came from the factory with the propper tool, avoid the cheap crush and go versions with the plastic sheilding, and add a bit of heat srink over the crimp surface. This will help keep the bare wire cleaner aswell as providing more strenth to the joint so the likleyhood of the wire breaking off at the crimp is far less.

    One of the main overlooked ground is the fuse block ground itself. The fuse block is located right above were wet floor mats and shoes created a damp enviroment. Most of the grounds within the block arent very high power but all suffer corrosion. Things like a stereo, the wiper motor aswell as factory wiring for fog lights run thru the block and then to the battery. Its also worth while if you have factory fog light wiring to find the connector under the coolant bottle where the wiring for the lights is split for left and right. Those connectors get particularly corroded. Cleaning it makes a world of differance. Adding a thicker piece of heat shrink over the whole connector helps a great deal.

    Hope this is helpful to anyone with Digi woes, or just looking to keep their car going strong.

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