Originally Posted by Benn0
You are collecting some good info there.... maybe 50% is the magic number. I'd love to set up this monitoring on my car, just haven't got the spare time to mess around with it.
This number is A
calculated value for %DPF , but whether it is THE
calculated value that the ECU works on we'll see.
One would assume that it would have to be up to a certain %full level before the ECU would think it worthwhile to use fuel to heat the exh and clear it. (60% ?)
Being just a calculated value, it seems to be steady for a few minutes and then updates suddenly (possibly some sort of moving average)
I've also today seen it just leap from 33% up to 47% and stay there for a minute or so and then drop down to around 34% where it was beforehand, which is probably because of the changing data for the calculated value.
One of the sensors it would be reading is the DPF differential pressure in (mbar) and that value will be reading all over the place rapidly changing with the changing gas flows in the exhaust system.
It would have to take into the pressure , engine speed intake air flow, and temperatures to calculate the gas flow and all of those vary so it's a moving variable rather than a steady value if it's not averaged over a time interval.
Iteresting all the different "advice" on how to drive with a DPF. This is my take on it:
- With short driving distances especially from a cold start DPF will fill up with soot more quickly. Temp from ambient to 200 C so is too cold and you are using increased fuel driving.
- Idling and sitting in traffic will also accumulate soot, as temp ~ 200 C. It will accumulate quite slowly as only about 1L/hr of fuel is injected, and that will not produce soot at a very high rate.
- On a longer drive where the temps go up to a slightly higher range 270-350C. A lot of the soot produced will burn off as it with react with NOx at this temperature range.
chemistry 2 C + 2 NO2 ----300C
------> 2 CO2 + N2 (moderate reaction rate)
Soot may still increase on the overall trip but at nowhere near the rate of driving around with a cold engine and never getting the exhaust temps high enough.
- Driving hard / towing. If you can get the temps up higher the soot will burn of faster. But, driving harder and using fuel at a higher rate produces soot at a higher rate too.
I'm not entirely sure that with this type of driving would actually reduce
the loading of the DPF in normal use. The reaction with occurs at only a moderate rate. Higher temps do speed it up.
- Exhaust temps 600 C ?. There is no way to get the temps up that high with driving even on a racetrack.
The soot burns very quickly at 600 C. And the only obvious way to do it is the active regen injecting (carefully measured) fuel to ignite in the exhaust.
The EGR also stops the recirc because we need some free oxygen for the fastest burn.
chemistry C + O2 -----600 C
-----> CO2 (rapid oxidation)
as the EGR is disabled there will probably be more NOx in the system too so the other reaction will also be occuring to help burn the soot.
The burn properly and quickly there would need to be a decent flow of gas (and O2) coming through the exhaust. I'm assuming Having the engine revs higher would be better than idling because the gas flow is more obviously.
I didn't know that idling for 2min disables the regen? That could be inconvenient.
I think VW's can regen at idle and I believe Toyota Coaster Bus (pain in the a$$) has to sit for 20minutes to do a clean at a higher revving idle.
If you've gotten down this far you must like reading, VW has a really good explanation on their ECU and their DPF system which generically is similar. I found this posted in the RAM1500 forum.
Lots of technical stuff in there - page 57 to 60 is where the DPF bit is so maybe just check those 4pgs
Originally Posted by XtRmn8
Mine is over 60% at the moment. I am logging my trips now so will report back once I see a regen occurring.
I am positive mine does a regen each time I see my instant consumption go up, which is normally every couple of week.
My instant consumption goes up from 6L to 8-9L at 100km/h and the last couple of times I noticed it lasts for about 15-20kms driving at 100km/h and than goes back to normal.
Mine must have been over 60% when it regen'ed. I saw it at 55% a day or 2 before and then drove about 400km on the highway before it regen'd. The DPF% was 6% when I checked it when i got home.