Download that vag dpf app and went for a drive. Before and after in attached. Soot level is down but shows oil ash residue is the same. bit sure what that means. Anyone?
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Looks reasonable I think.
Oil ash residue is the amount of ash that gradually builds up in the DPF over its life.
Each time a regen occurs and soot is burnt off, a tiny bit of ash remains, and it gradually builds up (if you're familiar with open fires or woodburning stoves, you'll know that every so often you have to empty the ash out as it'll never burn off....same principle here....except you can't empty it out!).
Anyhow the key thing you're interested in is Soot Mass - and this has two figures - "Calculated" and "Measured".
"Measured" is based on the pressure drop across the DPF as read by pressure sensors. This will rise, but can fall as well during regular driving (without an active regen occurring) if driving circumstances get the DPF hot enough for passive regeneration to occur. In my last car you'd start to see soot mass drop
slowly once above EGTs of ~300ºC in some steady-state driving.
"Calculated" only ever seems to rise until an active regen is triggered, I think it's a failsafe way of ensuring an active regen occurs just in case the measured figures become inaccurate due to faulty sensors etc, so your DPF doesn't get blocked.
When either one of these gets above a certain limit - I think this limit varies between engines/cars but on my last car was typically in region of 16-20g - AND the car is driving at a steady enough speed (not just urban stop/starting), an active regen will be triggered. When this happens, additional fuel is post-injected to raise the temperature of the DPF to around 500-600ºC. If the driving conditions allow, this will cause the soot to burn off and you'll see the level gradually drop. Once the figures get low enough (and note they won't both go to zero, on my last car the "calculated" only ever got down to a few grams, whilst the measured went right down) the active regen will stop, temps will return to normal, and the "time/distance since last regen" counters will be zeroed.
If you stop the car before an active regen is completed, it won't necessarily re-start an active regen until it's all warmed up, driving conditions are right (steady speed etc) again. There's also a minimum amount of fuel needed in the tank for active regens to occur (not sure what the number is, but if you're running in the red, regens might be prevented).
Looks like you got 351 miles between regens which sounds like it's in the right ballpark.
My last car (a Yeti, with the VAG CR170 engine) would maybe do around 2-300 miles between regens when stock, when I switched over to the Stage 1 remap I'd be lucky to get half that as the rate of soot loading increased - which means it was regenning twice as often and therefore doubling the rate of ash accumulation (so potentially reducing the lifespan of the DPF
). By 120k miles it was taking forever for each regen to complete, and was chucking out grey smoke during active regens, which I took to mean end of life of the DPF. Whether I was unlucky with a sooty map (it was from a very reputable tuning company) or whether this is an inevitable side-effect of tuning, I don't know - I doubt many people have really studied their rate of soot loadings closely enough to know? Hence my slight nervousness of remapping the Audi.
My stock BiTdi 320 seems to happily do over 500 miles between regens, I guess what's typical varies from one model of car/engine to the next, perhaps the DPF(s) on these are physically bigger and able to trap more soot ? I don't know.
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I'll have a look at that app. Cheers
