Seriously, at the kinds of temperatures available in normal operation downstream of the turbocharger you can't drive any soot oxidation directly with oxygen. It's too cold at the 300C - 450C you can reach in the DPF.I'm still not convinced it wouldn't be somewhat helpful. EGT temps while on the highway are higher than those at slower speeds and the DPF fills up slower as well. It would be nice if GM didn't dork up the emissions on this truck, but we have what we have. If someone had the money it would be worth it to Jet hot coat everything, but that seems like a lot of work, lol.
I have different findings with my CCSB Z71 4x4. My truck is at its happiest cruising 65 mph at ~ 1650 rpm. The DPF filling rate is very low. If I speed up to 75 mph at ~ 1930 rpm the rate goes up a lot (By rate I mean DPF full % increase per mile travel, not per unit time).I get what you're saying, but anecdotally I noticed slower DPF fill rates at faster speeds on the highway than at slower which corresponds to higher EGT temps and a larger soot load. Right now my ZR2 emission system is a total crap shoot since it regens every 100 miles, but in the past it was much better and I had increased intervals driving at 75 vs 65...
I have an ultra gauge that I watch the soot level on and what I base my previous posts on. When it's finished regenerating it is anywhere from 14-20% full still but usually drops a couple of percentage points in the first couple of miles after it's done.I have different findings with my CCSB Z71 4x4. My truck is at its happiest cruising 65 mph at ~ 1650 rpm. The DPF filling rate is very low. If I speed up to 75 mph at ~ 1930 rpm the rate goes up a lot (By rate I mean DPF full % increase per mile travel, not per unit time).
What you and I do not have available to us is a map of the soot mass rate coming out of the engine as a function of speed and load. Is the engine a lot smokier at 1900 rpm than at 1600? My truck suggests it is. But also keep in mind that 75mph demands a lot more power from the engine than 65 mph, so both rpm and load are changing. Your truck maybe acted differently, but is different again now with short intervals. Shortening intervals suggests a problem.
You say your truck regens every 100 miles. Are you looking at an OBDII reader to watch the regenerations happen? What soot filling level are you seeing reported when a regen finishes?
My guess is that the GM regeneration strategy is mostly driven from the DPF pressure sensors, since this approach is pretty reliable in DPFs that are primarily actively regenerated. If your regeneration intervals are shortening, there are a few possible causes:
1) It is possible that your DPF is filling with ash or is suffering from ash-bridging which makes it act like it is full of ash. This means the 'starting' pressure drop is high, so each regeneration can't reset you to empty, but just some fraction of empty. Basically.....your DPF is smaller now because it is full of ash and so it fills up faster.
2) Your engine is making more soot because of 'problems' and this soot is filling the DPF faster.
3) There is a problem with the pressure sensor, possibly drift or a downstream leak resulting in erroneous high pressure drop readings.
4) You are driving more aggressively, or have changed your use pattern of the truck without considering it.