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Modified Airbox

Discussion in 'A3/S3 Forum (8L Chassis)' started by Grant, Jan 23, 2004.

  1. Grant
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    Grant Well-Known Member VCDS Map User

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    [Jan 23, 2004]
    After reading some posts about oiled cone filters being harmful to the MAF sensor and induction kits perhaps not being worth the money, I have seen a photo of a modified S3 airbox where various holes have been cut out etc.

    Does anyone know where to find a template for such a project? Seems a cheaper option to try than a full induction system at the moment.
    #1
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  3. RichA3Turbo
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    RichA3Turbo ...Watching you! Staff Member Moderator

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    [Jan 23, 2004]
    [ QUOTE ]
    Drill said:
    Rich, what's your opinion on adding the extra feed, as shown in the Doc? /ubbthreads/images/graemlins/grin.gif

    [/ QUOTE ]

    Well in 2 minds really...

    Mind 1 says great idea.. extra air feed that sucks in cold air -GREAT

    Mind 2 says what a stupid place to put it... directly opposite the main feed so the air feeds will push air own each other creating air brrier stopping air going firectly into the intake...

    I guess the pressure wont be great so MAY no cause a problem but something to consider.

    Cheers

    Rich
    #2
  4. Ess_Three
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    Ess_Three Active Member

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    [Jan 23, 2004]
    [ QUOTE ]
    RichA3Turbo said:
    Mind 1 says great idea.. extra air feed that sucks in cold air -GREAT

    Mind 2 says what a stupid place to put it... directly opposite the main feed so the air feeds will push air own each other creating air brrier stopping air going firectly into the intake...

    I guess the pressure wont be great so MAY no cause a problem but something to consider.


    [/ QUOTE ]

    Rich,
    I don't think you'll find it's an issue.
    Even at 100 MPH any positive pressure fed into the airbox is only a few inches of watergauge - next to bugger all - so 2 x next to bugger all wont cancel each other out.

    Also, have you ever held you hand next to an exposed throttle body (or MAF or airflow meter) on full chat?
    Quite a suction I can tell you.

    So with an engine that's pulling a vacuum on the airbox volume, any supply restriction will show this up as a vacuum measured in the airbox...loads of air feeds only means you don't pull a vacuum - in effect you are supplying (or oversupplying) the needs of the engine.

    The trick is to get enough air into the airbox at high enough air speeds to provide positive pressure in the airbox even with the engine on full chat...that would be ram air! It would be nice to have...but to get it you'd need to have a lot od space for ducting, do a lot of aurodynamic work to the bumper and finally test it in a wind tunnel.
    Anyone have a wind tunnel at home? /ubbthreads/images/graemlins/wink.gif
    #3
  5. RichA3Turbo
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    RichA3Turbo ...Watching you! Staff Member Moderator

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    [Jan 23, 2004]
    [ QUOTE ]
    Ess_Three said:
    [ QUOTE ]
    RichA3Turbo said:
    Mind 1 says great idea.. extra air feed that sucks in cold air -GREAT

    Mind 2 says what a stupid place to put it... directly opposite the main feed so the air feeds will push air own each other creating air brrier stopping air going firectly into the intake...

    I guess the pressure wont be great so MAY no cause a problem but something to consider.


    [/ QUOTE ]

    Rich,
    I don't think you'll find it's an issue.
    Even at 100 MPH any positive pressure fed into the airbox is only a few inches of watergauge - next to bugger all - so 2 x next to bugger all wont cancel each other out.

    Also, have you ever held you hand next to an exposed throttle body (or MAF or airflow meter) on full chat?
    Quite a suction I can tell you.

    So with an engine that's pulling a vacuum on the airbox volume, any supply restriction will show this up as a vacuum measured in the airbox...loads of air feeds only means you don't pull a vacuum - in effect you are supplying (or oversupplying) the needs of the engine.

    The trick is to get enough air into the airbox at high enough air speeds to provide positive pressure in the airbox even with the engine on full chat...that would be ram air! It would be nice to have...but to get it you'd need to have a lot od space for ducting, do a lot of aurodynamic work to the bumper and finally test it in a wind tunnel.
    Anyone have a wind tunnel at home? /ubbthreads/images/graemlins/wink.gif

    [/ QUOTE ]

    Tis a good point! i'll go with mind 1 then /ubbthreads/images/graemlins/grin.gif

    #4

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