Max differential pressure for G450 ?

   #1  

benTSH

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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 à 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 à 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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DrPeter

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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
 
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benTSH

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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
 
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Eric

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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.
 
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benTSH

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ok understood :thumbs:

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
 
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golfi_vend

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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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benTSH

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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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benTSH

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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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