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Thread: dawes and needle valve for common rail?

  1. #51
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    Don't get me wrong.
    I am not saying you do not need to have more boost to get more air in.
    But boost is not all. What you need is to maximize the quantity of air getting in your cylinder, as measured by the MAF voltage.

    There is not limitation at 16 psi boost on the Di. The MAP sensor is not used.
    I can get 20 psi if I wish, although, beyond 18 psi, the increase of air you get is little are you are getting beyond the efficiency zone of the 2052 garett turbo.

    Getting a lot of boost down low is only creating backpressure, and little air is coming in. In other terms, you reduce the power/torque you can get from this engine. If you let it 'breathe' properly, it becomes another "animal".

    To move the 2.5T, you need torque down low, which you don't get if you keep the vanes closed too long, and beyond what is needed to get the initial turbine spin. You need to free the exhaust gaz, or you build too much back pressure preventing the cylinders to get rid of the exhaust gaz, making room for more fresh air + fuel. And you have reduced torque and ... driving pleasure.

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    growler2058 (20th May 2021)

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  4. #52
    The master farter
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    On my old Di the boost limit was 16psi, yes not via the MAP sensor as you say, just thats when the stupid thing would just a have hissy fit and go into limp mode, at 16psi, or 14psi if I wound in the needle valve for faster spool up. After changing out the MAF housing for a high flow housing, no limp, no hissy fits, nothing, I wound the boost out to 30psi and still nothing. Drove great.

  5. #53
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    Quote Originally Posted by mudski View Post
    On my old Di the boost limit was 16psi, yes not via the MAP sensor as you say, just thats when the stupid thing would just a have hissy fit and go into limp mode, at 16psi, or 14psi if I wound in the needle valve for faster spool up. After changing out the MAF housing for a high flow housing, no limp, no hissy fits, nothing, I wound the boost out to 30psi and still nothing. Drove great.
    This is a non-sense mate.
    reducing the MAF voltage makes the ECM believe there is less air than real. So, the ECM requests less fuel to the pump.
    Pushing boost, when reducing the MAF voltage, results in increasing the AFR by reducing the fuel injection.

    The only way to get the most of our 3.0 motor is to control the MAF value at all times by using the RPM signal, and manage the turbo vanes directly to maximize the MAF value. I explained all this in details on a Patrol site, and many abandonned dawes+needle for dawes + 2 needles, and now the magic box. That one makes an unbelievable difference.
    I am just sharing here the result of the 18 months I spent full time of deep analysis and development to overcome once for all the limits of my own Patrol owned for 21 years now.

    The problem with beliefs which have been going on for so long, is that it is hard to believe they were just wrong. I have been misled myself, so I know what it is ! I have been running my home made electronic VNT controller including a LIMP avoidance function, and my old lady became a young girl, climbing like never, to the top of the highest mountains I have around.

  6. #54
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    Crikey, if you Two Legends can agree I’m for sure reconsidering going back to a 3.0L
    By far the zippiest Patrol we’ve ever family owned, unfortunately had to get rid of it humanely clutch hauling Nags in our hills and had to revert back to a sluggish TD42T, did I mention SLUG


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    mudski (24th May 2021)

  8. #55
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    Quote Originally Posted by MB View Post
    Crikey, if you Two Legends can agree Im for sure reconsidering going back to a 3.0L
    By far the zippiest Patrol weve ever family owned, unfortunately had to get rid of it humanely clutch hauling Nags in our hills and had to revert back to a sluggish TD42T, did I mention SLUG


    Sent from my iPhone using Tapatalk
    Haha! I'll agree to disagree. I only supplied maybe 5000 of these kits worldwide and fitted maybe a couple of hundred during my time with the shop. But yes the ZD is quite zippy. Easier to drive than the TD in the burbs, but thats all its got going for it.

  9. #56
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    Making the ECU believe there is less air coming through by enlarging the inlet, or by simply adding one or two schottky diode in serie (costs only 10 cents each) with the MAF signal to reduce it by 0.15V or 0.30V have the same dual effect :
    1/ it suppresses the limp modes as the MAF voltage is reduced
    2/ it also reduces the fueling and therefore the power/torque as the ECM makes use of the MAF voltage to request the correct amount of fuel per stroke to the IP. Believing otherwise is just wrong. Just put a voltmeter on your MAF signal wire, and you will just see with your own eyes what I am saying here.
    And if you consider the MAF 'characteristic response' in volts to quantity of air in g/s , which is a 'log' curve (available on the net), you will see that missing 0.3V ( ie measuring 3.7V instead of 4V) makes the ECM believe there is 30% less air (!!) and therefore the ECM will ask 30% less fuel to the IP.

    Unless you go for a remap which increases the well known limp thereshold values, to suppress them, the alternative is to use the RPM signal to clamp the voltage just below the limp threshold(s) until the RPM goes above the associated RPM limit, after a delay of around 2s. Only electronics and software allows all these "subtilities".

    With the magic box VNT, and by managing the garett vanes properly, I can get more than 3.65V below 2000RPM ( limp at 3.55 ), and well above 3.88V below 2500RPM, 3.98V below 3000... etc. Never any limp, immediate spool, and max power and torque out of my engine at all Revs.

    Historically, people with limp used to screw the limiting screw to decrease the initial spool-up (same effect as adding a needle), but at the expense of getting a 'sluggish' Patrol. Some went on modifying the MAF enclosure (just to reduce MAF voltage which you can get with a simple non-expensive diode).

    People who have now moved to Magic box in several countries do get a full control of their turbo 'map', maximize the airflow at all Revs (and therefore the Torque and power) with boost under control, no peaks - no holes.

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