P139C Code

[Racket]

It has been brought up and discussed before - Adding a moisture trap (Inline) but my dive into the system gives me the take away that (It will not work)


From my (Detailed Operation) I need to find time for a final draft


Modifications to the EGR Tube & Hoses (Prevent or Lower the Moisture Risk)

It has been discussed all over the web about adding a moisture trap or desiccant filter bowl to the hoses – and many posts stating yes it will work, but has anybody actually installed a working solution – I cannot find one, sure the web leads you to believe it can be done but it lacks the real evidence of a proven working solution.

Here is my thoughts on this, first we need to understand how a (Air Tool) moisture trap works and what is required for the moisture to separate – One key factor (required) and that is – Velocity if we reflect from what we learned from above – At the (Hi-Pressure) reference port we have a high pressure but a low velocity, this takes away the key requirement for the moisture trap function of operation.

Air Tool Style (Moisture Trap)

Air inside the trap is forced to change directions suddenly (spiral or sharp turns) the air can turn easily but the water droplets cannot, so they are flung outward towards the walls of the bowl and gravity fed down into the bottom of the bowl – all from the air movement (Velocity) flowing in one direction and in a constant flow.


The EGR Tube Assembly (Pressures)

• Bidirectional Pressures (positive and negative)
• High Pressure / Low Velocity (Avg 3-15psig)
• Pulsed Exhaust Pressure
• Condensation, not liquid flow
• No steady flow direction

The moisture trap only works when there is a continuous flow and that flow is strong enough to move the liquid into the bowl – the DPFE hoses do not produce this requirement. So basically all the moisture trap will do is add volume to the pressure reference and may skew the sensor (bias) however still fall within the (Tolerance Bands)

The trap can provide (One Source) of collection and that is the gravity fed moisture that drains off of the DPFE sensor (Cooling Effect) Ref: DPFE Sensor Factor noted above. The reason this is a gravity feed down when (there) is no flow on the hoses, so the moisture has already reached the sensor and past the intended trap to contain it. The trap also will induce yet another (cold source) for condensation to occur – opposite of what you want to achieve.

Then you need to think about the added volume aspect of the equation, you would most likely need a trap on both hoses to equalize the DPFE (Zero Pressure Ref) in theory the sensor does have the +/- 0.30 Tolerance band, so this may not be an issue and one other item that you would need to address and that is the (Cold Start) frozen trap – this is going to alter the pressure reference and as well when it’s not frozen – where is the (full) bowl going to deliver the now pure moisture content – straight into the sensor you are trying to protect,

Desiccant Bowls

Desiccant requires a steady flow of air moving through the media (beads), the DPFE hoses have no steady flow and any vapor on the beads will saturate them almost immediately – so when they become fully saturated you end up with a dead volume bowl doing absolutely nothing as its intended function (drying) and also adding the same factors of skewing the pressure reference and then the same side effects of the moisture trap (once saturated) you are adding to the moisture problem you are trying to address.

Summary (Key - Take Away)

Because the upstream reference port sees high static pressure but very low velocity, there is no mechanism to move or separate moisture, making an inline moisture trap or desiccant filter ineffective and creates additional issues with the system


These are my thoughts on how a added (Moisture Trap) would function in the EGR System, feel free to experiment and play by trial and error.

1. It has not been proven (exactly) where the liquid moisture that ends up at the sensor (we visually see) (Main Source) - I feel its actually more at the plastic sensor housing being colder than the (EGR Tube) and gravity draining down into the hose

2. If not the sensor housing then its the (EGR Tube) itself (Temperature Variations) on the inside tube walls - EGR Flow (Tube Heats) - EGR Not Flowing (Tube Cools)

3. The flow in the EGR Tube after the EGR Cooler is already lowering the temp of the exhaust gas down to near the dew point

Ugh all I was thinking was a small/tiny descent unit - usually 2-3 bucks. All I'd want is to track how long until any color indicator reveals a lot of moisture was trpped.

Now it sounds like it's another insufficiently designed component and system.

Like the harness support for the radiator fan.

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[airline tech]

Did not mean to discourage anyone from trying a (Moisture Trap), its only my opinion that it would not work (as intended) - its actually something you could rig up as a test rig with different hoses and note if any reading changes occur (at the sensor) then monitor for moisture accumulation.
If is does not work, then simply reinstall the original hoses.