Since I got hold of AlfaOBD on my Android phone I can finally keep a continious watch over things like DPF pressure/temperature/clogging/etc/. (Multecuscan is brilliant, but not available on Android).
After numerous P1206 blocked/clean DPF errors I took the plunge and cleaned all the usual sensors/suspects. I then washed out the DPF with a combined overnight soak/jetwash using a strange combination of cola, brake cleaner and water! I am happy to say that the system is now seems fine with low pressure readings and no errors.
My conclusion is that this time the DPF really WAS clogged (but last year the pressure sensor broke and the symptoms were much the same). Apart from the normal sooty EGR valve I think my other engine bits are in reasonable health.
Anyway, during all this AlfaOBD has given me some surprising observations:
1-The clogging percentage value is a completely 'dumb' time based counter. It does not respond to the pressure readings or (as far as I can tell) driving style. It just creeps up continuosly as the engine runs.
2-The regen is also a dumb process. It is triggered when the clogging counter creeps somewhere past 80%. It is NOT triggered earlier if your pressure readings are getting too high (which is why you get pressure errors before it even tries to do a regen).
3-If the system is working properly then it will quite happily trigger a regen during normal A and B road driving with junctions. It will even carry on if you leave the car idling.
4-The clogging percentage will only update when the regen is stopped (either by completion or because you killed the engine). The new value seems to be purely a calculation derived from how much of the regen got completed (maybe back to only 60% for an interrupted regen, back to approx 20% for a full one). The figure then starts to crawl steadily upward again.
5-The most valuable thing I learnt was that the high revs/low load approach is not very good at raising the DPF temperature. On faster roads using 5th gear and a bit more load on the engine gave much steadier DPF temperature increase (although I guess high revs would help to blow out the crud, but would this be offset my pushing more soot into it in the first place?)
Hope this is some help to someone!
Martin
After numerous P1206 blocked/clean DPF errors I took the plunge and cleaned all the usual sensors/suspects. I then washed out the DPF with a combined overnight soak/jetwash using a strange combination of cola, brake cleaner and water! I am happy to say that the system is now seems fine with low pressure readings and no errors.
My conclusion is that this time the DPF really WAS clogged (but last year the pressure sensor broke and the symptoms were much the same). Apart from the normal sooty EGR valve I think my other engine bits are in reasonable health.
Anyway, during all this AlfaOBD has given me some surprising observations:
1-The clogging percentage value is a completely 'dumb' time based counter. It does not respond to the pressure readings or (as far as I can tell) driving style. It just creeps up continuosly as the engine runs.
2-The regen is also a dumb process. It is triggered when the clogging counter creeps somewhere past 80%. It is NOT triggered earlier if your pressure readings are getting too high (which is why you get pressure errors before it even tries to do a regen).
3-If the system is working properly then it will quite happily trigger a regen during normal A and B road driving with junctions. It will even carry on if you leave the car idling.
4-The clogging percentage will only update when the regen is stopped (either by completion or because you killed the engine). The new value seems to be purely a calculation derived from how much of the regen got completed (maybe back to only 60% for an interrupted regen, back to approx 20% for a full one). The figure then starts to crawl steadily upward again.
5-The most valuable thing I learnt was that the high revs/low load approach is not very good at raising the DPF temperature. On faster roads using 5th gear and a bit more load on the engine gave much steadier DPF temperature increase (although I guess high revs would help to blow out the crud, but would this be offset my pushing more soot into it in the first place?)
Hope this is some help to someone!
Martin
