Just about the cheapest mod you`ll see... *Update - Now with added boost*

Discussion in 'Diesel' started by StuMc, Oct 16, 2010.

  1. StuMc

    StuMc Moderator and Regional Host - Manchester Moderator

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    ...if it works that is!

    Found all the info for this over at TDI Club, where several people have been doing it for years.

    Known as the `Evry (or Avry) Mod`, it`s `simply` a case sticking a 1k Ohm potentiometer in the fuel pump harness to trick the ECU into dumping in more fuel than is actually being requested.

    Applies to pretty much all TDI engines (1Z, AHU, AFN, etc), and provides a decent slug of extra power for overtaking, dispatching tailgaters, embarassing chavs, etc.

    Much like those cheap chips you get on Ebay, but this can be switchable so you can use it only when you want.

    Not without it`s `dangers` if some people are to be believed (notably none of these detractors have tried it...)

    The danger of supplying too much fuel will be obvious to most, particularly high EGTs which can lead to turbo failure. TDI turbos are supposedly capable of nearly 1000deg (sustained), so the switchable nature, and thus intermittant use of the mod should keep you on the safe side. (Insert normal disclaimer here!)

    Anyway, on to the hardware;

    Assuming you have all the other materials required, then the 2.53 Maplin will charge you for this 1k Ohm switchable potentiometer, is all the cost of the mod...

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    Find a suitable switch blank, and modify to fit the pot (my car is a Mk3)

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    Wiring is really simple, but you need to do a few checks first;

    Using a multimeter identify the normally open contacts on the switch side.

    Then you need to determine which way the pot operates;

    The centre pole is the `common`, and depending which of the other two poles you use it`ll either operate; off, switch straight to 1k, then sweep down to zero, or off, switch to zero, then sweep up to 1k. For this application you want the former, which is the left pole on this pot.

    Start by soldering a jumper wire from one of the switch contacts to the common pole.

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    Next solder the two wires you`ll be running to the fuel pump harness. One to the left pole of the pot, and one to the other switch contact.

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    Now mount the pot in your switch blank.

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    Obviously this is a bit long, so a quick chop...

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    ...and suitable knob fitted (delibrately gone for this one as it looks suitably `Heath-Robinson` :lol:)

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    Also above you can see that in the `off` position the pot is out of the circuit, so everything will run as VW intended.

    Now switched to the just on position - 1k Ohms, and mod now in effect.

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    And now in the `All the way to 11` postion.

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    850 Ohms seems to be regarded as the lowest `safe` resistance to use, so I`ll be installing some sort of stop to prevent winding the pot too low accidently when on the go.

    The actual final position will only be determined after testing since each engine/ECU reacts slightly differently, so it could end being a little higher than 850 Ohms.

    Lost the light this evening so install and testing will be done tomorrow. Stay `tuned`... :lol: :thumbup:
     
    Last edited: Oct 16, 2010
  2. m1keh Forum Member

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    It works definitely. I have a tuning box here which i bought used off ebay and its still just a resistor added in but it only kicks the resistor in when the maf output voltage is over a certain amount.

    As for tuning it basically you'll find you hit a limp mode with too much resistance. On my car I found I was hitting this limp mode before smoke levels where unacceptable. If you are getting too much smoke then a dawes device in the line to the ecu can trick it into closing the wastegate more so you can get some more boost.

    Next stop is DIY chip tuning, im 75% of the way to completion on that one
     
  3. StuMc

    StuMc Moderator and Regional Host - Manchester Moderator

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    Most reports I`ve seen say, there is generally very little extra smoke, unless you wind it right down.

    A few say they run as low as 500 ohms, with masses of smoke (just as they want it), but quite often run into limp mode/pump shutdown (comically termed `Warp Drive Collapse`...).

    I`ll be setting it relatively high to begin with, then gradually wind it down to a comfortable level.

    Dawes Device looks good. Maybe one for later though. :thumbup:

    I`ve also seen one application where they`ve wired a micro-switch to the accelerator pedal so the pot is out of the circuit when off-throttle. I might go for similar when I`m happy it`s all working correctly.

    Keep us updated on the chip-tuning... ;)
     
  4. majic79 Forum Member

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    I've got an even better one for the old mechanical diesel XU TD engines that the frenchies use (205, xantia xm etc) - there's an enrichment calibration on the back of the pump with a security nut to lock it off. Mark the position of the screw, use a nut splitter or mole grips etc to remove the security nut, place a normal nut in it's place, screw in half a turn and lock off for instant fuel enrichment - cost, 0p. Tweak up wastegate spring to up the boost pressure and away you go

    edit: I wonder if there's a similar thing you can do to the PD engines.....
     
  5. StuMc

    StuMc Moderator and Regional Host - Manchester Moderator

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    The same can be done on the mechanically operated fuel-pumps on early VW diesels (GTDs, etc).

    The TDIs are ECU controlled so you need this method (or chip-tuning).

    PDs are a bit more complicated, so there`s little or no `home brew` tuning options.
     
  6. A.N. Other Banned after significant club disruption Dec 5th 2

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    Going to be keeping a close eye on this!
     
  7. StuMc

    StuMc Moderator and Regional Host - Manchester Moderator

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    Your 1Z-engined Passat is a prime candidate. Q-car-tastic! :lol:

    I`ll do some comparision videos too, so you can see how effective it is.
     
  8. Admin Guest

    :lol: at 11
     
  9. Dave

    Dave *Very Smart* Pedantic Old Fart Paid Member

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    StuMc:

    When I read the title, I assumed you were writing about yourself?
     
  10. Dave

    Dave *Very Smart* Pedantic Old Fart Paid Member

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    What about the cost of the new nut, the nut splitter, the spanner and the screwdriver?;)
     
  11. majic79 Forum Member

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    Pedant :lol: I've already got the tools and stockpile of nuts, but if you want it cheap, borrow them from your mate and raid his nut supplies! :thumbup:
     
  12. Dave

    Dave *Very Smart* Pedantic Old Fart Paid Member

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    Pedant is true!;)

    BTW I like your car.:thumbup:
     
  13. StuMc

    StuMc Moderator and Regional Host - Manchester Moderator

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    Very good... :clap: :lol:



    Well onwards to the fruit of today`s labour, the installation;

    This is where the switch blank lives...

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    ...disassemble.

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    Trial fit shows some Dremelling is required to the lower section of the hole.

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    Fits nice and snug now.

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    Installed in the car, and tested.

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    Now to find a suitable route from the engine bay into the car;

    This is about the only decent way in (coolant tank moved for access). It enters right behind the airbox,and is an absolute pig to get to, since you`ll need to remove the glovebox, lower dash section, and pull back the carpet/sound deadening. As you can see I`ve gone through this pain previously with the power lead for my amp/sub, so it was much easier this time.

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    I always find a piece of old washer tube to be the best `fishing` tool.

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    Back to the engine bay, this is the plug for the fuel pump that you`ll be tapping into.

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    1Zs and AHUs have 8-pin plugs, AFNs have 10-pin, but the two pins needed are the same; No.s 2 and 3, which are clearly marked on the casing.

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    The wire colours are; Pin 2 - grey with green trace. Pin 3 - white with green trace.

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    Strip back the insulation, and splice/solder one of your wires from the switch/pot. (You`re wiring in parallel, so it doesn`t matter which one.)

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    Repeat with the other wire, wrap securely, and replace the plug.

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    Back to the inside, and I`ve used bullet connectors, just for ease of removal/disabling if needed.

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    And now for real testing!

    With the engine at idle, turn the switch to the on position, and you`ll hear the revs fluctuate a little. (Here I`m switching on and off several times so you can here it.)

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    Now slowly wind the pot down until the revs drop, and the engine starts to struggle. Wind it back again until the idle stabilises. This is your sweet spot.

    As you can see, this is fully a quarter turn further than the bench test. It equates to around 700 Ohms. Lower than I was originally planning, but as mentioned every engine/ECU will be slightly different, so the final figure will be different for everyone.

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    A couple of comparison videos, mod switch off first;

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    And switched on (I`ll get a better one later)...

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    Much more urgent, and actually much smoother. There is some extra smoke if you give it full throttle, but I`ve found even 1/3 to 1/2 throttle is enough for most situations.

    Off the line it`ll spin up the wheels in the first two gears without much effort. Giving it full throttle from low down in third or fourth had the clutch giving a little slip.

    And here`s a naughty little clip of something that annoys me almost daily; This bus-lane is a part-time affair (not in use at all on weekends), but people still refuse to use it, diving in at it`s end so they`ll be in the correct lane just before the lights.

    30mph, 2000rpm (just coming on boost), and standard two second gap. Bus-lane is about 100-150 yards in length. I just beat the second car (Mini) to the line too... ;)

    [​IMG]

    So for 2.53, and a couple of hours work I`m well satisfied! [:D]
     
    Last edited: Oct 17, 2010
  14. Crispy 8V CGTI Committee - Club Secretary Admin

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    Yep This is a mod I done years ago pre playing with maps, it does work

    This using the wrong size varible resister, while driving in race harness part throttle, with a un-mounted resister

    what happened you turn it too much under part throttle, it takes off full chatter + some, you drop the resister while grabbing on the wheel and throwing out the anchor!

    of course you cant get the control to knock it back down, and your trying to stall the car coming up to a aroundabout........

    I also found 850-900 my sweet spot, been pulled from car ages ago

    I could explain how/why it works - but I won't!
     
  15. EZ_Pete

    EZ_Pete Forum Junkie

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    After a bit of experimentation, it may be worth replacing the 1K pot with a series combination of, say, a 680 Ohm fixed resistor and a 330 Ohm pot, giving you a full range of rotation on the pot without going outside the 1K - 700-ish Ohm range you want?

    Dunno for certain that you can get a switched pot in a 330 Ohm value, and I can't quite be bothered to search just now.
     
  16. StuMc

    StuMc Moderator and Regional Host - Manchester Moderator

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    Yeah, that`s one option I looked into too, but 1k was the lowest switchable pot Maplin had, and since it`s only a half turn required to the desired point, I`m happy for now.

    Quick launch vid;

    [​IMG]
     
  17. A.N. Other Banned after significant club disruption Dec 5th 2

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    Right, sounds like I need to get in on this asap! 1Z has new cambelt as of this eve (3.5k over schedule) so is now game on for some tuning.

    If you can give me any pointers to where I can get these items / how I can wire them up, I'll happily try this.

    Stu is yours a 110 brake?
     
  18. gigaz Forum Member

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    put a 400~500ohm resistor in series with the pot, so you can have "off" or 500 to 1500ohm
    its safer so you can't make a short circuit by accident ;)
    with a setup like that I wouldn't use my mobile(nor an electronic lighter) inside the car ,)
    if possible use shielded microphone wire and connect the shield to ground so it won't pick up interference.

    EDIT: Chris, you can get everything off Maplin (at least you could when I was in the UK 10 years ago) resistor should only cost a few pence, I could tell you part numbers and all but have thrown the Maplin catalogue away a few days ago [:D]
    oh, TV repair shops also have these ;)
     
    Last edited: Oct 18, 2010
  19. StuMc

    StuMc Moderator and Regional Host - Manchester Moderator

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    Get it done! :lol:


    Mine is a 90, but the `a*se dyno` says that`s up a bit (probably knocking on the door of 100bhp now. This includes any gains from blanking the EGR valve off), but it`s the low down torque that`s most signifcantly improved.

    To add another resistor in series; where I`ve used a jumper wire, between the switch contact and pot common pole, solder in the resistor here instead.

    I`m not too worried about winding this pot down too far, since it`s quite a wide sweep, and I`d have to go another half revolution `accidently` so not very likely.

    The avoidance of mobile use is not that much of a concern either, IMHO...
     
  20. gigaz Forum Member

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    in this case "use" is just having it turned on inside the car, as it communicates with the basestation without warning.
    just trying to save you guys from a broken ecu.. and its just a few pence more do do it properly ;) (well, better, properly would be a remap)
     

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