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  1. Some clarification please 
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    Hey guys,

    I need some clarification as to a problem i am having with underboost.

    Id like to grasp the concept first in a effort to making me understand more and hopefully resolving my issue!!!

    So my question is : what is the relationship between turbo boost and speed??

    I am under the impression through some logical explanation of mine, that a cars engine revs, makes boost etc the same in every gear and its the gearing ratios that determine how fast/how much power is created.

    Im getting underboost from 3rd gear onwards but not in 1st or 2nd which is blowing my mind!!!!

    Any help would be greatly appreciated

    Thanks!!!!
     
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  2. Re: Some clarification plz!!!! 
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    Quote Originally Posted by alevuc View Post
    Hey guys,

    I need some clarification as to a problem i am having with underboost.

    Id like to grasp the concept first in a effort to making me understand more and hopefully resolving my issue!!!

    So my question is : what is the relationship between turbo boost and speed??

    I am under the impression through some logical explanation of mine, that a cars engine revs, makes boost etc the same in every gear and its the gearing ratios that determine how fast/how much power is created.

    Im getting underboost from 3rd gear onwards but not in 1st or 2nd which is blowing my mind!!!!

    Any help would be greatly appreciated

    Thanks!!!!
    Engine code/type? Any modifications?

    Ian
    A4 B6 Avant Nogaro Blue
     
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  3. Re: Some clarification plz!!!! 
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    No mods

    Skoda octavia bkd 2.0tdi

    Tnx
     
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  4. Re: Some clarification plz!!!! 
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    less effort is required in 1 st gear and 2nd gear so the turbo can keep up. in 3rd it then needs to work harder but can't, so underboost comes up.
    Audi 80 tdi avant with 360,000 miles...
     
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  5. Re: Some clarification plz!!!! 
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    Right ok - is the underboost code "only" restricted to turbo and components (turbo, vac hoses, sensors etc) or can it be e.g. a fuel issue or temp issue or maybe even the engine condition compression etc???

    Tnx
     
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  6. Re: Some clarification plz!!!! 
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    the map sensor measures the pressure inside the inlet manifold and looks for a certain level against a set figure it has stored, the 'desired boost'. if the measured value falls outside of these figures at any stage then it comes up as a code and the engine will drop into limp mode. so underboost could be the turbo, or the amm, or indeed an engine problem. all it means is that the measured value as picked up by the map sensor is lower than the ecu wants it to be.
    Audi 80 tdi avant with 360,000 miles...
     
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  7. Re: Some clarification plz!!!! 
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    Right ok - im understanding you

    So far ive changed : MAF, MAP, EGR cooler, EGR valve cleaned and vacuum checked, Turbo actuator new and tested, Vacuum lines hold vacuum. Ive visually checked the intake pipes and cleaned them and they seem ok, yet to do boost leak test but.

    With this im freaking out that it might indeed be an engine issue as in - its screwed....

    While ive got you - as mentioned all the components hold vacuum, but my solenoid valve block starts buzzing like a min after i turn the car on, i then squeeze one of the vac lines n the buzzing stops......normal???

    Tnx for your replies mate - appreciated
     
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  8. Re: Some clarification plz!!!! 
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    couldnt say for sure, but do i remember crasher talking about the solonoid valve block ? maybe its leaking vacuum and stoppinmg the turbo actuator working. does it pull the turbo lever all the way when you start the car up. remember the turbo needs vacuum to make it work. not enough vacuum means underboost
    Audi 80 tdi avant with 360,000 miles...
     
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  9. Re: Some clarification plz!!!! 
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    It does pull the actuator up, now how far up its meant to go i dont know

    I've had a diagnostic check and the guys @ vw told me its making approx 1800mbar n requested was 2000 (or 2200 cnt remember) so im understanding the limp mode, just dnt know where to start with rectifying it
     
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  10. Re: Some clarification plz!!!! 
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    use a vacuum pump to see how far the arm pulls up, or bypass the solonoid block and put it direct to the vacuum source.
    Audi 80 tdi avant with 360,000 miles...
     
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