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best size mm for cold air feed

Discussion in 'A3/S3 Forum (8L Chassis)' started by Jonesy, Jul 29, 2007.

  1. Jonesy
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    Jonesy Member

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    [Jul 29, 2007]
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  2. Dave_Bayern
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    Dave_Bayern Slipping at 3.5Krpm

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    [Jul 29, 2007]
    £17 a metre!!!

    If I were you I'd use normal aluminium ducting at 10% the price per metre.

    Size would depend on where you intend getting this feed from , as you'd want your intake the same size as the ducting if possible.
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  3. Jonesy
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    Jonesy Member

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    [Jul 29, 2007]
    lol probably look elsewhere then, probably gonna try run it from the inner wheel arch, or maybe front bumper. To be honest i havnt really looked at the possibilties so dont even know if its possible. Ill check it out 2moro, where do u recommend getting the alumium ducting from?
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  4. abdus
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    abdus Top Gear VCDS Map User

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    [Jul 30, 2007]
    try B&Q for some ducting....
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  5. Jonesy
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    Jonesy Member

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    [Aug 1, 2007]
    ok thx ill have a look.
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  6. Ess_Three
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    Ess_Three Active Member

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    [Aug 2, 2007]
    You want the feed to the airbox to be bigger than the diameter of the hose from the airbox to the turbo. so you always have plenty of air in reserve.
    I used 100mm (4") duct.

    To fit that to an S3 you will need a FMIC though, as there is no room...but with a FMIC fitted you can run a 100mm duct from behind the front bumper to the airbox.

    Where in the front bumper to take the air from?
    Well if you are really sad you can measure the areas to determine which has the area of highest pressure (yes, I really am that sad) using a manometer and set the duct there.
    To save you the work...I found that a 100mm duct facing down towards the floor in the area behind the passenger foglight, level with the top of the foglight grille to provide the highest positive pressure area.
    It's only mb...but it helps.
    Keeping the duct in the high pressure area, but NOT pointing forward at that low level reduces the chances of picking up water from puddles, and the associated (expensive) hydrolock issues.

    Also, if you use a 100mm duct, get hold of a 100mm/4" subwoofer port to put into the end of the duct to smooth the airfolw into the hose...it also gives a firm place with which to mount the end.
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  7. Ess_Three
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    Ess_Three Active Member

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    [Aug 2, 2007]
    If you have a local Arco in your area, they will be able to supply black 4" HVAC ducting that will do the job very nicely indeed.
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  8. Dave_Bayern
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    Dave_Bayern Slipping at 3.5Krpm

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    [Aug 2, 2007]
    Interestingly, thats exactly where the CAI ends in an A3/Mk4 Golf configuration.

    Do you run cold air feeds to your brakes?
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  9. Ess_Three
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    Ess_Three Active Member

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    [Aug 2, 2007]
    Which make of CAI is that then Dave?
    My faith in tuning companies is slowly being restored...


    I did not.
    I removed the inner dirt shields days after getting the car new...
    And ran grooved discs with better pads or Brembos from then on and never had any problems with them.

    I also ran wheels with lots of air gaps...unlike the TT Cop style wheels which do nothing to cool the brakes!
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  10. Dave_Bayern
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    Dave_Bayern Slipping at 3.5Krpm

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    [Aug 2, 2007]
    Its a carbonio. I actually had to stop trimming the front grille for intercooler pipes to ensure that there was some protection for the filter.

    Best pic I can find whilst away from my pc is here:

    [​IMG]


    I have TT comps so am looking to run air feeds to the brakes. My normal track wheels are RS4 reps so plenty air gaps, but there will be a time I use the comps...
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  11. Jonesy
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    Jonesy Member

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    [Aug 3, 2007]
    thx for the infor guys, ive bought some ducting from b&q, a metre for 7 quid plus 2 metal clamps, unsure whether i can fit the ducting in the engine bay as its quite large but ill give it a go at the weekend.
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