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Thread: Max differential pressure for G450 ?

  1. #1
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    Max differential pressure for G450 ?

    Hi,

    After a short ride : 40 km on highway and 15 over interstate I've seen probably too much pressure on G450 :

    first part with DPF from 28% to 44% ( 62,59 grams of ashes )

    AVERAGE 178,5608412619 mbar
    ECARTYPE 110,3927556495 mbar
    ECART.MOYEN 85,8194944395 mbar
    MAX 692,5 mbar 3946 tours
    mini 16.9 mbar


    come back part DPF from 44% to 8% and then 15%

    AVERAGE 115,1602682849 mbar
    ECARTYPE 84,5817877386 mbar
    ECART.MOYEN 63,9932828197 mbar
    MAX 597,8 mbar 3900 tours
    mini 12.5 mbar

    it is better after the regen but not sounds good so as my engine has been touched by oil pump failure I dont want to spend too much on it as the engine work good except during regen DPF


    log at engine start:

    24.1 mbar Press. Difference Particle Filter
    2 mbar Press. Difference Offset what does this value means ?

    Thanks by advance

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  3. #2
    Ross-Tech Employee DrPeter's Avatar
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    Hello,

    - A G450 pressure sensor is reading the pressure 'difference' between two pressure lines.

    - The G450 pressure sensor offset is what the pressure 'difference' is between two pressure lines.

    Hope this helps,

    drpeter
    Last edited by DrPeter; 04-27-2016 at 05:31 PM. Reason: grammar

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  5. #3
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    Well not really but it's my fault : I'm french lol so I often can't translate very well

    The 2 mbar "offset" is so tiny and doesn't change so it is nearly insignificant even if maybe sometimes this value is higher but I'm still wondering its meaning; I need a 2,21 gigowatts lightning of knowledge Doc lol

  6. #4
    Ross-Tech Employee Eric's Avatar
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    The offset is going to increase with the engine output. Just like trying to flow lots of water through a small hose, vs a tiny amount of water. You get a considerable pressure drop (offset) with a high flow in a restricted passage, while it tends towards zero with a smaller flow. Your exhaust gas flow at idle is not very restricted by your DPF even when mostly clogged. However at higher rpm and load, things start to get crowded and that's where you'll see a difference. So really you should be looking at that offset at stabilized highway speed for significant measurements, or even full throttle at a given rpm.
    You ain't metal till you got a clutch pedal

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  8. #5
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    ok understood

    What could explain the fact that offset doesn't change and is 1 or 2 mbar ?

    Maybe I'm wrong because I didn't watched this data very seriously as only Press. Difference Particle Filter evolve during a ride

  9. #6
    Verified VCDS User golfi_vend's Avatar
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    Hey guys the offset isn't supposed to change. Offset is the fixed value when you adapt the Diff.Sensor for the first time and and zeroes out the possible measurement error in engine-off state.

    The MVB differential pressure does change. The possible pressures are noted(at least in my car) in VCDS pop-up.
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  11. #7
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    Here is my curves from turbo :




    http://dl.free.fr/b2sT2fIT7

    ok I have a lot of lag under 3000 RPMs ( and had an oil pump failure 40 000 km before now but with had stopped the engine immediately) but maybe it is normal ? ( a turbo can't push instantly I guess )

    Here I was between 32% and 36% of particules into the DPF and will do the test again after the next regen ( soon I guess ... )

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  13. #8
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    here are my curves with low DPF % :





    First curve not good but the next three more interresting : with a differentiel graph between request pressure and real


    3.6% 5.4% 7%

    the first area is smaller than the nexts even if the right one is a litte better than the one in the middle so it seems that the less particule in the DPF the better it works but I'm not a mecanic ;-)

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