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I decided to buy an AutoEnginuity scanner with Ford Bundle as a a belated B-day gift for myself--like 5 months late.
Just tried it briefly this morning and it seems pretty easy to use. I didn't even have to read the manual. I don't care for the red LED's on the OBD dongle. Red to me means something wrong. Wished they were green instead.
There's a "distance since last regen requested" and a "Distance since last trial regen" counter.
What's a "trial regen"? An incomplete regen? I did indeed shut the last one down early.
So I'm curious--what parameters and levels typically trip the regens to start? I see DPF pressure and the temperature sensors and all, but I assume the DPF pressure plays the biggest role. Is there a typical pressure drop given some exhaust flow rate (which I assume is partly a function of rpms and boost) that would say "it's about time" for a regen?
What are typical values/symptoms that would indicate if the DPF is near full, end of life, or plugged (assuming a CEL doesn't come on first)
Here's my typical 40minute drive home from today. Starting from cold engine at work, there's quite a bit of stop and go and 40-50mph driving. I took the log output from AE and plotted it in excel chart.
Top 3 lines are pre-CAT, post-CAT, and post-DPF temperatures.
Bottom line is my DPF pressure in psi
I left my EGT-A off since it's all over the place between 300-800F
Note that post-CAT temperature lags pre-cat, and the DPF-outlet temperature lags even more. There's quite a bit of thermal inertia if that's the right term (sorry, I'm an EE and I almost flunked thermos) in the CAT and much more in the DPF. That also means if the DPF is bloody hot, it takes more than just a few minutes of idling to cool it down even if EGTs are low.
The last 10minutes is a drive up a hill where I live, hence a rise in temperatures
I thought driving at high EGT's going up the hill would heat up the DPF and help passive regens. From this, one has to drive at high EGT's for a while before the DPF gets hot enough (>600F?) to do anything.
I get the feeling one trigger for regens is a running average DPF pressure reading accumulated over some period of time since I'm pegging the default max DPF pressure limit setting whenever I'm accelerating moderately, but no regen yet.
I'm due for a regen in about 100miles. Hope to catch it
That thermo that is retained in the cat/dpf is called passive regen. That heat buildup in there is good actually. Helps to prolong the time between the active regens.
I thought(??) soot starts burning around 600F in our DPF's. I'm thinking the fact that the DPF is so massive, it takes quite a bit to heat it up, and once it's heated, it takes a while to cool off. I idled for about a minute before shutting down, but it was still sitting at 400F+ though my EGT's were around 300F.
Got lucky this morning and caught a regen. First half of the regen was in stop-and-go traffic with the rest on freeway. Only bummer was my laptop automatically powered off (!$#@!) so I lost the last 6minutes of the regen before I was able to power it back on and resume recording.
As expected, I blew a cloud of smoke for about 30-60seconds the moment I started moving after sitting at a long light
So it looks like the way regen works, it gradually increases heat from the CAT to maintain approx 100F temperature rise at the output of the DPF compared to inlet temperature. And it keeps increasing as long as there's a temperature rise.
I'll have to get another capture to see when regen stops and hopefully I'll remember to keep my laptop from powering off
Only complaint so far is having to quit and restart the program every time my laptop is shut down for any reason. Otherwise it won't recognize the USB security dongle even though it's plugged in already. And then it takes a few minutes to link up to the engine to do whatever before being able to do anything
Need 2 USB ports --one for USB security key and one for the OBD dongle
Here's what appears to be a passive regen occuring right around 425F. Note the output temperature of the DPF is higher than the output of CAT ever got. The only way the output of the DPF is hotter than its input must be due to soot burning.
The first half of chart was me getting on and then stuck in 5mph freeway traffic. As soon as it opened up and I got up to freeway speeds and things heated up, the passive regen occurred.
The DPF pressure on the lowest graph roughly correlates with throttle and load. My DPF is pretty full and feels way overdue for a regen. Maybe these passive regens are keeping the regen from starting sooner (??)
I caught this on the way home tonight. The truck was feeling very constipated and as soon as ECT hit 161F, the "cleaning exhaust" message flashes just as I entered the freeway. Notice the DPF pressure was pegged while heating the DPF at a rate of 100F/min. Regen stopped on its own about 2 minutes before I pulled into my driveway.
Note how abruptly it finished by itself right around 6:27 (heat output of the CAT turns off) while the DPF was still producing heat. The last 5 minutes of driving was up a small grade if that has anything to do with anything.
I also note that DPF outlet temperature rose slightly above 1200F for about 1 minute total just before it stopped. It seems like there was still more soot burning, and as earlier, EGR was turned on immediately afterwards as long as throttle was 0%.
I logged commanded and actual EGR on this capture. During regen, EGR commanded is always 0%, but there are instances where the EGR actual was sitting 0.16~0.32% for minutes at a time. Strange because during regular driving with no-regen, 0% commanded always = 0% actual. I don't seem to see any correlation with anything. I surmise if EGR is turned on during regen, it's to quickly control the amount of oxygen in the exhaust and therefore control/limit DPF temperatures(??)
As soon as regen stopped, EGR was increased upwards of 40% at 0% throttle...probably to ensure any further DPF combustion is stopped. When EGR is cycled normally at idle, I rarely see anything beyond 15%
EGT's were all over the place between 600-900F with steady throttle.
I'll bet the gradual temperature rise of the DPF during heatup is done to prevent cracking the DPF substrate.
"Distance since last completed regen" stops incrementing during regen and is reset to 0 when regen stops on its own. If regen is interrupted, it does not reset and continues incrementing.
"Distance since last trial regen" is zeroed during regen and resumes incrementing as soon as regen stopped. I'll bet scan tools that are able to indicate when regen is in progress simply monitor this PID for a zero value
There are 3 PIDs that time how long the DPF temperature exceeded 3 different and unspecified temperature levels. Unfortunately, I turned those off earlier.
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