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Thread: Dawes Valve?

  1. #1
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    Angry Dawes Valve?

    Hi, I'm new to the arcane world of Diesel GU ZD3.0 and I have been told that I need a Dawes valve.

    I have been looking closely at my Boost and EGT gauges on a recent trip and I noticed the Boost gauge was climbing up to 15lb and then suddenly dropping when no apparent acceleration was happening .

    I have heard a Dawes valve will prevent over-run of the Turbo, so - where can I get one, and get one fitted in WA?

    I have paid about $4K on some upgrades (3" exhaust and the gauges + Catch can and Filter) and I'm not very happy with the standard of installation.

    I really need someone who will not give me the runaround and give me real story and also assist with the installation

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  3. #2
    The master farter
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    The Dawes will limit the boost level, also give a more linear power curve, you can also add a needle valve in the mix and then you can adjust the spool up rate of the turbo. In my opinion, do both. And no need to mount the needle valve in the cab for on the fly adjustment, as you will eventually be told to do. Its a waste of time, both valves are a set and forget setup. Ive fitted too many of these things to care. As for anyone in WA, got no idea sorry.

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  5. #3
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    I second what Mudski said.
    My boost was going up and down like a roller coaster for no apparent reason. Now I have a similar product to a Dawes and it makes a huge difference. They are easy to fit yourself and come with instructions for installation.
    Don’t set it to over 16 psi or you will get limp mode especially in cold weather.


    Sent from my iPhone using Tapatalk Pro

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    As above. I think the dawes and needle on a 3L Di, especially the CRD is a MUST in my opinion.
    CRD factory boost is a Yoyo that needs to be tamed for smoother boost and spool rate, your motor will thank you for it.
    2005 TD42TI

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    Hi down under,

    I am a french owner of a 05/2000 3.0Di Y61 PATROL (ZD30), with 160 000km, which I bought brand new... 18 years ago.
    I did nothing on it until reaching 150 000km. No problem whatsoever. Good stuff.

    I cleaned the intake manifold, blocked the EGR, and replaced the standard/old exhaust by a 3" stainless exhaust which I imported from Australia (your lovely country).

    I was not happy with the way the ECU was managing the VNT, which was creating a 'hole' in pressure rise when revs were going up at around 2100 RPM ( more or less as described by Chaz on his website).

    I fitted a Dawes Valve and needle valve last week to try and fix this, but am still not happy with the result.
    I set up the Needle valve as explained in many posts and on Chaz's web page ( around -550mbar vacuum in the actuator circuit).
    On a vacuum gauge, what I see is that once the dawes open, the pressure in the intake manifold drops by 3psi, and then has more than difficulties to raise again.

    In no way do I get a smooth and continious increase of pressure whilst revs go up once the dawes is open.
    It looks to me like the VNT is closed all the time ( and the pressure goes up nicely and quickly from 0 to 14 psi with my current setting of needle/dawes valves, and then when the Dawes open, that's it. Pressure drecreases suddenly.

    I have tried different settings , but in fact, the VNT stays closed untill the dawes open, but opens too widely in one go, thus creating a significant hole in pressure.


    I tried to set up the Needle, so that the vacuum pressure was like -650mbar at idle, to compensate for when the Dawes opens and suddenly adds around 250mbar of positive pressure, giving a vacuum of around -400mbar, but this was still not good either.

    It looks like the Dawes acts like an ON/OFF valve, whilst I was thinking that the more the pressure goes, the more it would leak, and then would reduce the raise in pressure, bu opening wide the VNT.

    What am doing wrong ?.

    I am a member of a french PATROL Forum (30 000 members), but nobody has this system in use (yet).
    Your help would be much appreciated in teaching all of us how to do this setting properly.

    Pleade dont' laugh, but it looks like I am a pioneer in my country ( unbelievable isnt'it ?) when you guys have done this ... 10 years ago ?

    Thanks guys

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    nobody ?
    I found a solution to get a progressive opening of the variable geometry by improving Chaz's schematic as follows :
    Any comment welcome.

    Capture décran 2018-08-31 à 19.44.27.png

  9. #7
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    Error in my posted diagram.
    This is the correct arrangement :
    Capture décran 2018-09-01 à 12.22.46.png

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