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    Thread: 1.8t swap to an MK1 using factory ECU - N249 valve stay or go?

    1. Member mullantf's Avatar
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      05-18-2020 09:20 AM #1
      As part of my swap, I'm going to have the ECU flashed to eliminate post cat O2 sensor, secondary air injection, N80 monitoring (still want the function but not the monitoring).

      What about the N249, the ECU control for the bypass valve? Stay or go? I read that it limits boost spikes by given the bypass valve a bit of a head start on throttle lift off, versus waiting the extra half second for vacuum to build in the manifold. Worth having?

      What else should I eliminate?

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    3. Senior Member Vegeta Gti's Avatar
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      05-18-2020 12:34 PM #2
      Search. This topic had been covered thousands of times in the last 20 years. No lie.

      Built my in 2008 without asking a single question online. 250k miles later @486whp.

      Sent from my SM-N975U using Tapatalk
      :HOMEGROWN MOTORSPORTS..SingerVehicleDesign...1:4.9 SuaSponte #13Dead Rabbits. Ungluck on IG. MKIforLife
      Quote Originally Posted by .Ant View Post
      What vegeta said.

    4. Member hushdc's Avatar
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      05-19-2020 12:27 PM #3
      Quote Originally Posted by Vegeta Gti View Post
      Search. This topic had been covered thousands of times in the last 20 years.No lie.
      Truth. Vegeta is right. I just finished up my MK1 1.8t swap a week ago without asking a single question. I gathered all my info here on the vortex, google and else where. Every single question about this swap was answered by simply searching.

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    6. Senior Member Vegeta Gti's Avatar
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      05-20-2020 12:49 AM #4
      Quote Originally Posted by hushdc View Post
      Truth. Vegeta is right. I just finished up my MK1 1.8t swap a week ago without asking a single question. I gathered all my info here on the vortex, google and else where. Every single question about this swap was answered by simply searching.


      Sent from my SM-N975U using Tapatalk
      :HOMEGROWN MOTORSPORTS..SingerVehicleDesign...1:4.9 SuaSponte #13Dead Rabbits. Ungluck on IG. MKIforLife
      Quote Originally Posted by .Ant View Post
      What vegeta said.

    7. Member mullantf's Avatar
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      05-20-2020 08:49 AM #5
      I did find lots of posts where folks said they eliminated it as part of a swap, but it was only mentioned in passing. Other threads that were not swap related went into significant detail and seemed to conclude that it provided a useful function.

      Hence my question. I'm not looking for a "just get of it" easy answer, but rather some incite as to *why* people decided to remove or leave it. It's obviously quick and easy to remove, but has anyone actually thought about it first?
      Last edited by mullantf; 05-20-2020 at 08:49 AM. Reason: typo

    8. Senior Member Vegeta Gti's Avatar
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      05-21-2020 03:49 PM #6
      The data you're seeing, that is helpful, is a decade old. Things have progressed.

      Sent from my SM-N975U using Tapatalk
      :HOMEGROWN MOTORSPORTS..SingerVehicleDesign...1:4.9 SuaSponte #13Dead Rabbits. Ungluck on IG. MKIforLife
      Quote Originally Posted by .Ant View Post
      What vegeta said.

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