CR170 DPF soot loading rates: standard vs. Stage 1

Hi all

Greetings from the UK Long time member, very infrequent poster...

I have a 2011 Skoda Yeti, with the CR170 CFJA engine. Just covered 50k miles.

I've recently had a Stage 1 tune (est 205-210bhp) from a well known UK tuning company, and have been logging DPF soot loadings with VCDS - both in standard and Stage 1 tune.
I usually do two 40mile journeys each day. Half of each journey is open road, 60+mph, the other half is slower urban traffic.

Was wondering if my findings are typical, or whether I possibly have an issue with the car.

Standard tune:
The "Calculated Soot" value rises slowly, and takes around ~250-300 miles to reach 16g, at which point a regen is triggered.
The "Measured Soot" value tends to rise on average by maybe 2g per journey; at points during the journey it will rise a little more than this, but other times it will reduce slightly when I'm cruising fast enough for DPF exit temp to be over ~310ºC.
In summary, regens tend to be triggered by the rise of the Calculated Soot value, every 250-300 miles.

Stage 1 tune:
The "Calculated Soot" value rises similarly to standard tune, maybe a little faster if I really use the power, but generally the same.
The "Measured Soot" value rises constantly and fairly quickly. In the course of the same 40 mile journey above, it will rise by maybe 12-14g. At 16g it will trigger regen. The levels rise during normal, light-throttle cruising as well as full power use.
In summary, regens are triggered by the quick rise of the Measured Soot value, every 60-80 miles.

I think the soot loading with Stage 1 tune is excessive, however this is a standard CR170 Stage 1 tune from a very well regarded company with plenty of happy customers; I've logged requested vs. actual boost & airflow for them over a full-throttle run in 4th gear and they think everything looks in order, they've double checked the map too.

So I'm wondering if there is some underlying issue with my car ?

Does the soot loading behaviour of the standard tune sound normal ?

Any thoughts or suggestions of things I can check/log would be very welcome.

Thanks

I should add - there have been no errors logged at all.

So...

Measured soot is based on the delta pressure sensor across the DPF and the flow rate calculated over the DPF. Pressure/Flow gives a number that can be turned into a soot mass.

The "calcualted soot" is based on essentially a set of lookup tables in your map based on speed and load and a few correction factors....

Your remap will not have affected calcualted soot as you have noticed - this would never get remapped by any but the most diligent of tuners... People that diligent would also probably not have made the new tune extra sooty...

However your seeing the measured soot rise at a rate that is much higher than before is because your engine genuinely is either. A) producing more soot or B) the flow rate calculations got broken by your remap.

In my experience you will have option A - lots more soot... You will probably find that the smoke limitation on your remap has been changed to a level that is producing far to much soot - this then is depositing high amounts of soot in your DPF and that leads to the pull up you see.

To combat the above effect the easiest way is take the car back to your tuner and ask for an EGR delete also.

Many thanks for the useful reply.
Can you expand on why the EGR delete would help ?
I'm in two minds about an EGR delete; if my understanding is correct, it will lead to longer warmup times, and also I think it's used to help maintain DPF temps too ?
My tuner mentions that the "lambda limiters" are set to stock values. Any idea what this means - is this the "smoke limitation" that you refer to, or something else ?
Thanks again

Hmm... If the lambda limiters are what you say they are then with them set to stock values it should not be so smoky...

The egr delete will essentially reduce the amount of soot your engine produces by a scale of around 10 so will take much longer to fill up the dpf....

I would however before looking elsewhere - try using VCDS to force a service regen and drive the car for 30mins on the motorway until the soot readings are back to 0.

Thanks again.

And another question, sorry

Why do you suggest the service regen, will that do something different to the normal regen process?

Also - do you know if it's possible to restrict the EGR on a euro CR170 using a plate/gasket with a hole ?

Cheers

The reason I suggest the service regen is it can be that your normal regen hasnt lasted long enough one time and that will cause the amount of soot in the filter to be too high. And each regen is not long enough to clear it out.

A service regen should last longer and therefore ensure its completely empty..

OK thanks.

My journeys are usually long enough for the regen to complete - I've been logging with VCDS every day for the last few weeks, and the regens always take values back to 0.

I've asked my tuner whether they can remove or reduce the EGR amount.

I guess deleting EGR completely will be best in terms of reducing soot production, but won't be good in winter if it makes the engine take longer to warm up.
Was wondering if it's possible to significantly reduce EGR, but in under some conditions, have it function as normal to aid warmup. I don't know what's possible in terms of EGR maps though.

Thanks for your help!