Definitive list of what you can and cannot remove/bypass/resistor on OEM 1.8T

Discussion in '1.8 & 1.8T' started by rubjonny, Jul 15, 2011.

  1. rubjonny

    rubjonny Administrator Staff Member Admin

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    As title, after lots of reading around I've found various conflicting answers on this subject, and since I dont own a 1.8T I cant try any of these myself. I need to know what I can and cant bypass safely if I'm going to make good quality engine conversion looms see! Specifically, a list of what can just be cut, what needs to have a resistor inserted to avoid limp and what needs to be coded out.

    Info I have so far:
    V101 - SAI pump:
    Can be removed along with all associated wiring and relay. Sometimes a fault code will be logged, but it does not result in limp mode.

    G130 - After CAT/2nd Lambda:
    Can be left dangling but is not ideal. Best way is to have this coded out by someone who can fiddle with the ECU code.

    N112 - Secondary Air Inlet valve solenoid:
    Bypass with 2 watt 330ohm resistor? code/limp?

    N80 - Carbon canister valve:
    Bypass with 2 watt 330ohm resistor? code/limp?

    N249 - Turbocharger air recirculation valve:
    Bypass with 2 watt 330ohm resistor? code/limp?

    F88 - Power assisted steering pressure switch:
    Wires can be bridged together to simulate pressure?
     
    Last edited: Jul 15, 2011
  2. Admin Guest

    why 2 watt out of interest?
    Big arguement on vortex as to the need for anything larger than 0.5watt in the system.
     
  3. rubjonny

    rubjonny Administrator Staff Member Admin

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    just what someone used and had working, certainly less than the uber resistors you see some chaps use :)
     
  4. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    Do not know where the source was that that "info" however it is for these reasons I would not recommend "bypassing".
     
  5. rubjonny

    rubjonny Administrator Staff Member Admin

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    This info has come from here and several other forums. its all quite conflicting too with people saying they have done it with resistors and no problems, or some have had problems, or whatever. No good info to be found really like the above, with in-depth reasoning behind the functions.

    so out of all of those, which if any will put the ecu into limp mode if disconnected, plus which of them should never be bypassed as they perform a critical function. the N249 is the main one, some people say they deleted it with no worries but im pretty sure this is not a good idea.

    so in short for each of them:
    1. should you bypass them? yes/no
    2. which ways can you do it? code is out/disconnect/resistor
    3. with 2, what are the consequences of each method? fault code only/limp mode/other consequence

    with the pressure switch is it best to just leave the wires disconnected then? i assumed this was so the ecu could flag if the PAS wasnt working :lol:

    basically for me, all i care about is how I should make my MK4 conversion looms. should i just leave all the wires alone, or are there things I can do to them to make the installers life easier?
     
  6. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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  7. rubjonny

    rubjonny Administrator Staff Member Admin

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    perfect thanks :thumbup:
    do you or anyone else know someone who can do the required coding out of features?
     
  8. drewbar Forum Member

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    Ive got all the above disconnected and lambda run in the atmosphere, this doesn't give any apparent running problems and made decent power on the rollers recently. Obviously the EML light is and i'd like to sort this so who can code out the about on the factory ECU?

    And of course how much is it going to cost me? The ECU is already mapped.
     
  9. MUSH Forum Member

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    cant remember....?
    Left this open circuit as my mk2 had no pas, however is a good option should the car have pas, and you simply run the 1.8t pump.

    I used 7 wattt resistors, when all the info i could find was regarding 10 watt resistors. The only reason i used the 7 watts instead of a lower rating like the 2 watt you have mentioned as i was unaware if the resistors would heat up. I also wrapped them seperate to the loom just incase there was a heat problem. There wasnt really much info kicking around when i was playing about with this.
     
  10. badger5

    badger5 Club GTI Sponsor and Supporter Trader

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    the thing I dislike and dont ever advise resistoring is, the resistive load is not the same as the inductive load on solenoids.. Feel your solenoids, they are never warm.. Fell your resistors and the fact you have to use >5w resistors, they run hot.. and ask yourself what the ecu thinks about having to drive this additional power.. Some ecu's fail as a consequence.. Some are luckier.. I never resistor out.. but just leave the solenoids electrically connected and moved somewhere out of sight..

    my 2p
     
  11. Ditchyboy Forum Member

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    Bill,
    If you leave the solenoid connected but out of site / not connected wont this cause fault codes? How can you get around the codes problem?
     
  12. welshwizzard88

    welshwizzard88 Forum Member

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    Resistor wattage makes no difference unless you really need to be able to dissipate the heat.

    I use lots of resistors at work the only time wattage is a isuse is if is in a power supply or amplifier type application. High estate ones make great heaters
     
  13. badger5

    badger5 Club GTI Sponsor and Supporter Trader

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    it wont throw connection problems no.. It may fault function problems (incorrect flow for SAI for example, and EVAP,) but they can be coded to no set MIL off
     
  14. badger5

    badger5 Club GTI Sponsor and Supporter Trader

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    again... I will say just one more time before I let you cook your ecu's output stages

    do your solenoids run hot, or even warm to touch???? Nope.
    The resistors WILL... and ask yourself where did this extra POWER come from to make heat... poor ickle ecu

    maybe your lucky maybe you're not....
     
  15. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    Also to add many PCMs have diagnostic feed back via the power stage.
    Some power stages do not only allow constant earth path either, more like PWM!

    Sure people use resistors as bodge, but this is not the best way. Get the ECU to someone who understands the strategy/firmware and get them to inhibit the function or tweak the diagnostic counter. Then you can run the ECU as a simpler standalone.
     
  16. rubjonny

    rubjonny Administrator Staff Member Admin

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    right then i think the solution is leave ecu loom alone and direct customers to this thread, they can make their own choices. best option is to get required functions coded out. since most will be getting the immobiliser removed anyway might as well get the required functions coded out at the same time :thumbup:
     
  17. Admin Guest

    in coding out do you not need the resistor trick then?
     
  18. rubjonny

    rubjonny Administrator Staff Member Admin

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    aye, tells ecu not to worry about unplugged stuffs
     
  19. badger5

    badger5 Club GTI Sponsor and Supporter Trader

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    nope. not true for all of them
     
  20. priceygti Forum Member

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    Ok then what can be coded out without using resistors?
     

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