204 DSG intermittent momentary power loss

[mmi]

oh, ok, im a complete newb to logging and what not, ill have another go today.
do I need to drive the van for each log to be saved?

1) blockmap - engine not running - just turn ignition on and create the blockmap file (cold engine is just fine)
2) Turbo actuator test - engine idling (cold engine is just fine)
3) Turbo changeover valve test - engine idling (cold engine is just fine)
4) EGR test 1st - engine idling (cold engine is just fine)
5) EGR test 2nd - hot engine idling - thus a bit of driving to warm up the exhaust

 

[mmi]

log files from earlier

Thank you very much for the log files - and especially having markers in the files - helps to pinpoint and confirm the moments of the issues.

Some preliminary thoughts... about the last logged session (of total of three in the recording).

Large scale view in time of markers whereabouts​

A downselected period for closer view - from 760 to 775 seconds​

Well, probably the most illuminating period because of

• high vehicle speed = high engine load
• only few gear changes
• also "things" happen at slower rate thus easier to understand

General conditions - speed, engine revs​

No noticeable glitches in engine speed signal - not even by zooming in.

Turbo actuators​

Obviously at about 764 seconds the pedal was floored, the gear was stepped down to 4th at 764 seconds, and stepped up into 5th at 768.5 seconds.

Turbo vane actuator (blue) and turbine changeover actuator (grey) reach and stay at their "full blast" positions.
Turbo wastegate (red) regulates charge pressure until...

Charge pressures as seen by the ECU​

I guess the pressure drop seen at 767 and 770.5 seconds drive the ECU to start to close the wastegate (squared red in picture one above).

Air mass flow & engine torque​

Air mass flow is in sync with charge pressure - quite naturally. And of course the recorded/calculated engine torque follows.


QUESTION - does this happen also on gear 7?

In the log the 6th gear was used and marked at 830 seconds (below).

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It has been remapped, though I don't think it was a very good one.

My guess is that the turbo just can't handle the excessive air flow and the airflow in turbine vanes simply suddenly "slips" ???

Unfortunately I don't have reference values at the same conditions (4th gear full blast at and above 3800 RPM). Only thing similar by speed I found was only 130 grams/second of air flow - just barely half - but that's on 7th gear so also number of cylinder fill-ups is about half of what would have been on 4th gear.

Of course a culprit could also be a misbehaving manifold pressure sensor (which are known to get clogged). Or misbehaving wastegate actuator or valve.

 

[Cog Head]

Thank you so much for your input & analysis

It happens in all gears if I pull away wile towing the caravan, I booted it in the logging to try to simulate that.
I’ll get the block file and other tests you requested today.

I’d like to get to a point where we can isolate a certain part, or few suspect parts that I need to look into, rather than shooting in the dark at random parts and getting nowhere with it.

We aren’t going away to Europe with it this year, but I’m building a bit of a fear of the motorway hills around Santander in Spain, anyone who’s been there will know them.
The thought of attempting to scale those hills with this high demand / load power dropping out, isn’t very appealing at all.

 

[Cog Head]

turbo and recirculation test

 

[Cog Head]

blackcap from earlier too, the engine wasn't completely cold, it was left parked after towing said caravan home after the weekend.

 

[mmi]

turbo and recirculation test

Thank you.

Turbo actuator test - sweeps a few times from min to max - OK as expected based on the logged journey.



Turbine changeover valve test - sweeps a few times from min to max - OK as expected based on the logged journey.



Also both pressure sensors read same value as seen earlier thus no suspects there either.



Also the wastegate can also be tested using VCDS but the recorded data already shows that it operates correctly.
Just fullfilled/edited the procedure into the posting

Post in thread '[T6_measured] 01-Engine - Built-in tests for turbocharger'

13 Oct 2024

01-Engine - Basic Settings​

IDE07136-Test of wastegate actuator (only Bi-Turbo)​

HOW-TO​

Engine running​

VCDS > Select > Engine > Basic Settings > IDE07136-Test of wastegate actuator​

Select "Measuring Values"​

Pick up the following data items for monitoring:

IDE00021 Engine RPM​

IDE00347 Air mass: actual value:​

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

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

IDE07744 Particle filter: air...​

• mmi

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I’d like to get to a point where we can isolate a certain part, or few suspect parts that I need to look into, rather than shooting in the dark at random parts and getting nowhere with it.

I think the issue is that the requested 3.5 bar charge pressure is simply too much asked. Stock CXEB does at maximum only 3.1 bar.

Still interested to see results of the EGR test - to evaluate DPF condition - as the blockmap data a kind of suggests some degree of blockage there.

4) EGR test 1st - engine idling (cold engine is just fine)
5) EGR test 2nd - hot engine idling - thus a bit of driving to warm up the exhaust

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

23 Apr 2023

So it seems - inevitable P0401.

Well, visited a VW garage to be tested - the van had accumulated 30 events in ECU's memory since July 2021 (since 20 months now). Eventually managed turn on the emission light at event number 31 - thus had a priviledge to have EGR flow tested. The result - pending - the ODIS went to an unending loop without a concluding result.

Meanwhile, I think I have reproduced the EGR flow test using VCDS. However, I don't have any reference value to estimate the degree of EGR cooler blockage. Neither did ODIS tell the reference value (should have told but the computer...

• mmi
• egr p040100 t6_measured
• Replies: 83
• Forum: Engine, Gearbox, Exhaust, Drivetrain

• 

 

[Cog Head]

Once again, thank you!

I’ll try to get the EGR & watergate actuator tests done this evening.

Does the van need to be driven or will a period of ticking over be ok to get the exhaust hot enough?

 

[mmi]

Does the van need to be driven or will a period of ticking over be ok to get the exhaust hot enough?

Whatever is convenient for you - we'll be in the right ballpark anyway - as the actual temperatures are recorded



S3 is DPF input
S4 is DPF output

 

[Cog Head]

I’ll do this in the morning, I just realised the van is parked rot next to the neighbours house, I don’t think they’d appreciate me running tests at 22:21