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Thread: Boost Pressure

  1. 1st March 2012, 07:01 PM #1
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    Question Boost Pressure

    Have fitted a digital boost gauge, coupled directly into the inlet manifold and have done a few test runs with vehicle under various load conditions.
    Gauge indicates an ambient pressure just below one atmosphere (around 13.8psi) on idle (we are 200m above sea level here) and shows a maximum pressure achieved during the test drives of 35.5psi.
    After reading a number of posts on the forum, I understand that I should expect an ideal boost pressure of around 20psi give or take.
    I would assume that this is 20psi above the ambient pressure and I am reading 35.5psi ... therefore, in reality, I actually have about 21.7psi boost.
    Is the way I am interpreting this correct .... or not !
    If I am correct, is this too much boost? ...I don't have any surge issues at the moment.
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  2. 1st March 2012, 07:53 PM #2
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    see what fitting a boost gauge etc does, makes you doubt the beast and sweat the small stuff.
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  3. 1st March 2012, 08:38 PM #3
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    IMHO your boost gauge is wrong...

    at 200m above sea level you should be seeing somthing like 14.4ish psi (as opposed to 14.7@ sea level)
    Dave

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  4. 1st March 2012, 08:58 PM #4
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    Does it read 0 or 14 when the engine is not ticking over?. I do not have one but would have thought that it will measure boost over atmospheric so you are getting one plus atmospheres boost I suspect?
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  5. 2nd March 2012, 11:56 AM #5
    biggin
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    It's hard to believe that your setup measures absolute pressure rather than gauge pressure.

    I can see three possiblities:
    • your sensor and gauge do not match
    • the gauge is out of calibration
    • all is correct and your are somehow getting up to 35.5psi
    Try removing the sensor and check it against a known air pressure, or something.
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  6. 2nd March 2012, 01:28 PM #6
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    that it reads absolute isnt so strange, thats what the ECU is working off of and if its electronic it may have a switch on the back of the gauge that will allow you to flick it from absolute to gauge.
    Last edited by Blknight.aus; 2nd March 2012 at 11:38 PM. Reason: typo, when someone works out what and EVU is let me know.
    Dave

    "In a Landrover the other vehicle is your crumple zone."

    For spelling call Rogets, for mechanicing call me.

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    Archaeoptersix 1990 6x6 dual cab(This things staying)


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  7. 2nd March 2012, 03:11 PM #7
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    Quote Originally Posted by John W View Post
    Does it read 0 or 14 when the engine is not ticking over?. I do not have one but would have thought that it will measure boost over atmospheric so you are getting one plus atmospheres boost I suspect?
    Hi John W,
    Actually, its reading 13.7 with engine off
    13.6 on idle
    35.5 max boost achieved

    Also, made a mistake with our property altitude ... is 600m ... not 600ft (200m) :-(
    Last edited by rapserv; 2nd March 2012 at 03:13 PM. Reason: additional info
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  8. 2nd March 2012, 03:15 PM #8
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    Quote Originally Posted by Blknight.aus View Post
    IMHO your boost gauge is wrong...

    at 200m above sea level you should be seeing somthing like 14.4ish psi (as opposed to 14.7@ sea level)
    sorry Dave,

    made a mistake with our altitude ... should be 600m ... not 600ft.
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  9. 2nd March 2012, 04:18 PM #9
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    13.7 is near enough for atmospheric pressure at 600M, sounds about on the money for max boost in a disco td5 to me Deefer TD5's can be made to go consistantly higher as they dont have the wastegate modulator.

    I'd have to go back and have a look but I from memory the disco TD5 is allowed some "overboost" in certain circumstances
    Dave

    "In a Landrover the other vehicle is your crumple zone."

    For spelling call Rogets, for mechanicing call me.

    Fozzy, 2.25D SIII Ex DCA Ute
    Tdi autoManual d1 (gave it to the Mupion)
    Archaeoptersix 1990 6x6 dual cab(This things staying)


    If you've benefited from one or more of my posts please remember, your taxes paid for my skill sets, I'm just trying to make sure you get your monies worth.
    If you think you're in front on the deal, pay it forwards.
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  10. 2nd March 2012, 11:08 PM #10
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    Quote Originally Posted by Blknight.aus View Post
    13.7 is near enough for atmospheric pressure at 600M, sounds about on the money for max boost in a disco td5 to me Deefer TD5's can be made to go consistantly higher as they dont have the wastegate modulator.

    I'd have to go back and have a look but I from memory the disco TD5 is allowed some "overboost" in certain circumstances
    Almost certain it is actually the other way around: because of the wastegate modulator, the overboost limit on Td5 Discos is set slightly higher (240 kPa) then on Deefers (225 kPa). Stand to be corrected though.

    Rgds
    Matt
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