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my vacuum woes

Discussion in 'A3/S3 Forum (8L Chassis)' started by DaveA3, Nov 30, 2010.

  1. DaveA3
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    DaveA3 Audi A-Trizzle!

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    Hi All,

    I swapped my boost gauge over to a brand new one as i dropped my old one on the floor and it had a mind of its own. Anyway now i can see proper reading i realised last night that my vacuum is a bit all over the shop:


    It starts at -20hg as normal

    Then if i put a bit of throttle on idle or moving it goes down to -26hg then after a while it goes to -25hg -26hg bouncing between the two each time i left off the throttle. if i idle after a lil drive it sits at -26hg.

    Does this mean i have a leak somewhere? :think:

    cheers
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  2. S3BAM
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    S3BAM Member

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    Most probably i changed all the boost hoses on my old scooby had same prob cable tied them all up cured it.

    What gauge are u running as some cheaper runs seem to flutter a bit my Led one(already on car when i bought it) on my Octy Vrs flutters a little
    Last edited: Nov 30, 2010
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  3. s3dave
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    s3dave TFSI Hybrid

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    you can put a little reducer in the pipe that stops the fluttering
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  4. DaveA3
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    DaveA3 Audi A-Trizzle!

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    yeh i have the reducer and it does stay steady on the number its reading but it just doesnt sit nicely. i cable tied all the pipes a few months back i should get to see if i missed one anywhere. i think its the pipe off the manifold that has the check valve in between as i have a blue silicone one on instead as my standard one was split. I remember the originalone has a reducing pipe inside the end so its probably not as snug as that. hmm ill have a think and check it out later :)

    cheers
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  5. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    Idle vacuum is less on initial start up as the throttle is held open more on cold start/fast idle until warm... the idle vacuum should increase once past that and will also increase when you let off the throttle as the ECU will close the throttle completely... you will see this for example if you are off the throttle going down a hill...

    <tuffty/>
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  6. DaveA3
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    DaveA3 Audi A-Trizzle!

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    ahh i see but would u say that -26 is still a leak somewhere?
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  7. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    If you had a vac leak then I would expect the vac figure to be more positive than negative...

    <tuffty/>
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  8. DaveA3
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    DaveA3 Audi A-Trizzle!

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    hmm ok just strange how i can have more vacuum than normal lol
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  9. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    Because by changing the boost gauge you fixed a leak?

    <tuffty/>
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  10. DaveA3
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    DaveA3 Audi A-Trizzle!

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    not that i mean i thought the standard vacuum was -18 to -20 but somehow i have more. guess im just being paranoid
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  11. s3dave
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    s3dave TFSI Hybrid

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    Is it a cheapish gauge Dave? it may not be calibrated correctly...-26 would mean your rev counter would be showing 6/700 nearly stalling?
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  12. DaveA3
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    DaveA3 Audi A-Trizzle!

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    it was £40 not a cheap one at all really. At full boost it holds at 18psi and sits at 0 when off etc
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