204 DSG intermittent momentary power loss

[Cog Head]

Thank you so much mmi
Your input is incredible.

So, it looks like the DPF is coming off this weekend!
Now I have to decide what to do with it, clean and keep it, or something else, I’ll have a chat with one of our resident tuners to get their takes on what to do.

I feel like I should replace / clean the EGR valve and cooler assembly and also remove and clean the inlet manifold to get it all cleaned up, being gummed up with carbon cannot be helping the engine one bit.

 

[Cog Head]

Also, I’ll give the van a good kicking later on today to see if the forced regen has cured / helped elevate the power loss issues.

 

[mmi]

Also, I’ll give the van a good kicking later on today to see if the forced regen has cured / helped elevate the power loss issues.

If VCDS is onboard I would propose to use the setup below

IDE00021 Engine RPM​

IDE00075 Vehicle speed​

IDE00347 Air mass: actual value​

IDE00589 Fuel pressure​

IDE04090 Exhaust temperature bank 1​

IDE07736 Turbocharg.2 compress.outlet: press.sensor 1 bank 1: raw value​

IDE07738 Charge air cooler inlet: pressure sensor 1 bank 1: raw value​

IDE07742 Cylinder head: pressure sensor 3 bank 1: raw value​

IDE07744 Particle filter: air pressure sensor 1 bank 1: raw value​

IDE07783 Turbine actuator 1 bank 1: posit.feedback - Raw voltage​

IDE07791-ENG180364 Turboc.1 turbin.bypass valve 1 B. 1: pos.feedback - Raw voltage-Voltage_16_usigned_1000​

IDE08138 Bypass valve for turboch 2 turbine inlet: activation​

The DPF pressure and, exhaust gas temperatures are added.

 

[mmi]

Meanwhile,

after regents EGR test

Differential pressure across the DPF - after DPF regeneration​

Interestingly the pressure peaks across the DPF are significantly less than on the previous illustration (now 26 mbar vs. 65 mbar previously) in post #138 204 DSG intermittent momentary power loss.

This would be perfect result if it would only last. Wondering if this is an indication that only small area of the DPF ceramic comb is passing the exhaust and thus the DPF would show excellent performance for a brief moment only.

The gradual decrease in pressure is probably because the DPF (S1, S2) cools down during the test. See below

Temperatures along the exhaust pipe​

 

[Cog Head]

So that makes a lot of sense with how the van feels when it looses power, it’s like you have to work the van up to that point, then when it happens, if I don’t lift, the power dropping outs become more and more frequent and last longer, until I eventually lift off for fear of blowing something expensive into the stratosphere.

May I assume that a dirty inlet manifold would also add to the restriction of flow through the engine and add to the problem?

 

[mmi]

May I assume that a dirty inlet manifold would also add to the restriction of flow through the engine and add to the problem?

Surely every point of air flow loss will count when pushing the limits.

However, as the turbo 2 pressure sensor is well before manifold (in fresh air) and it also detects charge pressure loss I would think the pressure loss indeed is turbo based. Otherwise the pressure would have remained high at the sensor.

Of course as the turbo is a kind of chicken and egg type of thing - it need exhaust flow to build up charge pressure, which is needed to build up exhaust flow...

 

[Cog Head]

It’s still behaving the same as before, at high revs and high demand / load.
I don’t have any log data just yet, I’ll get that in an hour or so.

 

[mmi]

It’s still behaving the same as before, at high revs and high demand / load.
I don’t have any log data just yet, I’ll get that in an hour or so.

Perhaps you could after the logging journey let engine idle and make yet another engine blockmap recording?

 

[Cog Head]

latest log is attached

 

[Cog Head]

blockmap attached

 

[Cog Head]

I hope the log file is ok, I went on pick her ladyship up from work, while I was waiting for her I paused the logging, then resumed it when we left to head back, it was logging on the way back but when we got home it had stopped saying stopped for safety purpose.

 

[mmi]

I hope the log file is ok,

Thanks - as there were some different parameters recorded it's even more interesting.

Unfortunately the DPF pressure was left behind - not recorded

IDE07744 Particle filter: air pressure sensor 1 bank 1: raw value

Also the grouped UDS requests was not ticked this time - slowing down the data logging somewhat

---

Anyways, below a couple of plots of data before the pause

Exhaust temperatures​

The exhaust from the engine reaches about 800 °C and seemingly saturates there (see in more detailed below - a kind of saturated - flat - "waveform")

Exhaust temperatures - zoomed in​

Which brings back an earlier posting of @nazarko1984 (below) - saying there actually might be an exhaust temperature limiter at 800 °C

N

Post in thread '204 DSG intermittent momentary power loss'

6 Aug 2024

Hi MMI,

I went to the garage who made a remap. This is normal behaviour when you do remap. There is EGT limiter set to 800C. Now they move it to 880C.
What I learned it is still safe to 900C but to be avoid any issues I decided to do not reach that high temp.

Thank you for your inputs.

RG.
Marek

• nazarko1984

• 

Perhaps also your remapper can confirm this?

---

Anyways, the other things are the same - charge pressure and wastegate fluctuations at power loss

Charge pressure​

Wastegate activation​

Fuel pressure​

 

[Cog Head]

Ahh nuts, sorry about that, it was setup in a bit of a rush as I was running late, I’ll give it another go.

Well spotted on the exhaust gas temperature, I’ll be making contact with a new tuner soon, I’ll show them the EGT chart and ensure they make the necessary changes to remove that from the equation.

I’ll still get the DPF off the van this weekend and give it a really good clean, it can do no harm, and I’ve already got 2x5L bottles of the cleaner solution now.
I think I’ll do a bit of a write up on it with plenty of photos, I’ve struggled to find one.

 

[n10n]

This would be perfect result if it would only last. Wondering if this is an indication that only small area of the DPF ceramic comb is passing the exhaust and thus the DPF would show excellent performance for a brief moment only.

This rings some bells - the pressure drop goes up fast after regen and evens out when more soot accumulates to pores:

Post in thread '[T6_measured] 01-Engine - Built-in test for EGR'

2 Aug 2023

Basics of Diesel Particulate Filter (DPF) Operation | CTS

This CTS Knowledge Base article describes the fundamentals of diesel particulate filter (DPF) operation. The article provides a summary of the filtration processes occurring in the DPF, various types of DPFs in common use, and differences in filter operating and regeneration strategies...

www.ctscorp.com

• n10n

• 

I would think if large part of the comb would be blocked even after a regen, the pressure drop would also stay high?