What's inside a DPFE Sensor (Pics Inside)

[ctechbob]

Decided to tear my old one apart tonight.

Answer is, not much. The actual sensor looks to be a tiny strain gauge, which makes sense.

When these things were $20 I'd say just replace them, now I'm thinking if maybe a small packet of desiccant inside that tube wouldn't give longer life to it. There is no flow through the piece so it is just small bits of pressure moving back and forth, as long as you didn't plug the whole thing, a small mesh type bag of desiccant shouldn't change much. The moisture is probably effecting the bond between the small chunk of silicone and the substrate (just a WAG).

Backside (Small tube runs to the front chamber, larger tube to the back.

Anyrate, a little middle of the night nerding for everyone.

Front side. Note the water is just on this side.

The actual 'sensor'. Some form of strain gauge, piezoelectric would be my guess. Not an expert though.

The other side:

Circuit board. Not much to see here:

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[Racket]

Curious what the direction of flow is?

 

[ctechbob]

Curious what the direction of flow is?

There's no flow. Just pressure on the front and back. It is just measuring the difference in pressure between the two sources. Nothing actually flows through the sensor. That's why I think there could be some desiccant put on the one side, you wouldn't be blocking the flow since all that needs to move through it is pressure and as long as it wasn't packed completely full it should still work just fine. I could be wrong, I'm certainly not trained in fluid dynamics.

The front is sealed from the back by way of that small sensor chip.

 

[Racket]

I zoomed in to see the moisture.

So somewhere condensation is happening. If it really is in some pressure loop (the two different sized barbs might be a clue) I guess one side is reference and the other for metering. Seems like a simple chemical treatment like for marine applications would be all, but I can see where some type of dessicant somewhere might extend the life of these. Probably would add fourteen cents to the cost.

I used to work for a company called Pressure Systems Inc. and we hand soldered, bench calibrated and potted air pressure sensors for the aviation industry. This looks similar but I recall our sensors were for R&D so didn't get exposed to the elements much but this looks somewhat similar.

Otherwise I would spend five bucks and added some barbs to slip something on the pressure side to stave off failure:

 

[Apples]

The culprit is called... Heat!

 

[airline tech]

The water vapor in the exhaust flow being acidic over time damages the seal on the Piezoelectric
Pressure Transducer which affects the ability of it reading correct pressure.
The transducer measures the pressure difference between both sides (Upstream = Exhaust and Downstream = Intake) of it and converts it to a voltage. (So, its measuring pressure drop)
Upstream Exhaust - High Side Pressure = Large Tube
Downstream Intake - Low Side Pressure (Aka Ref Signal) = Smaller Tube

So, when the EGR valve opens the Low side pressure is Higher, than it is when the EGR valve is closed. (This is how the PCM reads the Flow)

So, when it fails, improper reading of flow, it is not reading correctly, the sensor will sense no flow when there is actually flow.
To put it another way, it is not reading that the EGR valve is open when the EGR valve should be closed. (Idle and Low RPM / Load) or a low EGR flow is now equaling no flow and the PCM is controlling the EGR valve with that reading.


If you can picture a juice bottle pressure seal cap - after you have opened it and take your finger and press on it - it pops back up is an easy way to describe what the transducer is.

 

[5thranger]

Decided to tear my old one apart tonight.

Answer is, not much. The actual sensor looks to be a tiny strain gauge, which makes sense.

When these things were $20 I'd say just replace them, now I'm thinking if maybe a small packet of desiccant inside that tube wouldn't give longer life to it. There is no flow through the piece so it is just small bits of pressure moving back and forth, as long as you didn't plug the whole thing, a small mesh type bag of desiccant shouldn't change much. The moisture is probably effecting the bond between the small chunk of silicone and the substrate (just a WAG).

Backside (Small tube runs to the front chamber, larger tube to the back.

Anyrate, a little middle of the night nerding for everyone.

Front side. Note the water is just on this side.

The actual 'sensor'. Some form of strain gauge, piezoelectric would be my guess. Not an expert though.

The other side:

Circuit board. Not much to see here:

You just unleashed the next pandemic when you opened that up.

 

[P-38Ranger]

Even though there is no flow during operation there is air “migration” so it could be contaminated over time. My thought is that, is FORD aware that their supplier has delivered a known failure part, or has the vendor, or vendors supplier, omitted a process that would mitigate this failure.
A whole new can of worms!!!

We all know that the ancient Ford Explorer Firestone tire incident was caused by Ford eliminating the department that tracked this kind of trend, and ended up paying 100 time more in lawsuits than that dept ever cost.
Is this an EPA issue? Do they fail before 100000 miles?

From the Motorcraft site.

Durability test specification- 10-years/150,000 miles

 

[Grandaccess]

oh no, one more thing to worry about
could you just dry it out and reseal it LOL

 

[KJRR]

We all know that the ancient Ford Explorer Firestone tire incident was caused by Ford eliminating the department that tracked this kind of trend, and ended up paying 100 time more in lawsuits than that dept ever cost.

Well here is some of the Explorer/Firestone story....
https://www.ranger5g.com/forum/threads/p-a-schilke-back-stories.18745/post-389144

 

[P-38Ranger]

Well here is some of the Explorer/Firestone story....
https://www.ranger5g.com/forum/threads/p-a-schilke-back-stories.18745/post-389144

Thanks. Interesting.

 

[ctechbob]

oh no, one more thing to worry about
could you just dry it out and reseal it LOL

If only it were that easy. The moisture is getting into the substrate and either damaging the bond between materials or altering the electrical properties of the assembly, or both.

What sucks about the whole ordeal is it used to be a $20 sensor and now it is pushing $70.

We're all still going to replace them from time-to-time, it just flat sucks that they've tripled in price.

If they come back in stock at Rockauto at the $19 price I'm buying 4 of them.

 

[Msfitoy]

If only it were that easy. The moisture is getting into the substrate and either damaging the bond between materials or altering the electrical properties of the assembly, or both.

What sucks about the whole ordeal is it used to be a $20 sensor and now it is pushing $70.

We're all still going to replace them from time-to-time, it just flat sucks that they've tripled in price.

If they come back in stock at Rockauto at the $19 price I'm buying 4 of them.

Also buy gas at $4 before it gets to $40...everything is going to sh!t...?

 

[ctechbob]

Also buy gas at $4 before it gets to $40...everything is going to sh!t...?

No doubt. If it kept longer I would.

 

[NotBudule]

Your not supposed to open those !!!

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