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    Thread: Help! Does the IAC connection point matter?

    1. Member
      Join Date
      Dec 20th, 2003
      Location
      San Antonio, TX
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      326
      Vehicles
      1981 Scirocco 2.0 16vT -- 2000 GTI
      07-27-2020 12:59 AM #1
      Ok, I did search here and Google, couldn't find this asked anywhere.

      Right now I just have my IAC drawing from ambient outside air with a K&N filter on the end. I'm contemplating connecting it to the intake boost tube like the it was designed to be.

      I don't think i'm getting enough air into my engine by letting the vacuum at idle draw in air through the IAC, I feel I may need the slight pressure to get the expected amount of air into the engine at idle. My AFR is awful at the moment.

      For me and my pipe setup, it would be worlds easier to tap into the boost tubes before the CoPot.

      So......
      Does it matter if the IAC (ISV to some) draws in air from a location before the CoPot? In other words: upstream of the CoPot. Stock, it draws from the boost return, if you do the ISV bypass it moves it to the intake tube, but both of those are after the CoPot (downstream). In a custom piping setup, would it be ok for me to draw the air into the IAC from a location in the boost tubes after the IC but before the CoPot?

      In other words, does the CoPot need to sense the amount of air the IAC is sending into the intake manifold like CIS-E needs? ..in cis-e the ISV raises the fuel metering plate.


      thanks!
      Ryan

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    3. Member
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      Dec 20th, 2003
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      1981 Scirocco 2.0 16vT -- 2000 GTI
      08-04-2020 01:13 AM #2
      bump...anyone?

    4. 08-09-2020 02:28 PM #3
      I don’t think it matters where it draws the air from as long as the output from the valve is into the intake manifold after the throttle body, the valve also exhaust over boost back into the return pipe or with the reroute kit back into the charge side


      Sent from my iPhone using Tapatalk

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    6. Member sdezego's Avatar
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      Apr 23rd, 2004
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      Hurricane Central FL
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      '90 Corrado | '62 Harley Panhead
      08-21-2020 01:54 PM #4
      Digi is based on Speed Density not Metered air like a MAF, so the ISV will have no effect on Fueling.

      However, the ISV should not be open to Ambient, unless you want to throw away boost as Stock did into the Boost return after a certain PSI. You can gain 1-2 PSI by routing the ISV into the Boost side (i.e ISV re-Route)

      If your ISV can't compensate enough, perhaps you have your idle screw in too far.

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