Driving today mostly freeway and was getting close to a regen. When it happened I monitored it carefully, then wrote the data to a file. I am using an ODBLink MX WiFi talking to ForScan on an iPhone 6 Plus. Data points are approximately every 30 ms. I threw it into XL to chart it, almost brings XL to it's knees, about 64000 data points in this chart:



X axis is time in minutes, Y is EGT temps at the four measurement points, fuel delivery which I believe I have displayed in L/h * 10 to get it on the same scale, and DPF soot in g/l*100. The chronology is also interesting for the diesel nerds among us. At the start of the chart I am just finished accelerating onto the freeway (880 North at Brokaw). The regen starts at about 4.5 minutes. Temperature gradients are pretty steep with downstream lags. You can't see it at this scale, but the fuel delivery is jittering between what would be normal (around 13 L/h) up to about 45 or 50 L/h in pulses. At about 9.4 minutes I get off the freeway at Mission Blvd and there is about 2 miles of city streets with two red lights. At about 11.8 minutes accelerate back on the freeway (680 North). Climbing Sunol grade from about 15 - 18 minutes (this is maybe 800 ft 5% grade I'm guessing). Over the pass and down the other side note the drop in fuel delivery. But normally on that downgrade there would be zero fuel top to bottom, here it was pulsing on every few seconds to keep the heat up. The next few humps in EGT and fuel delivery are the hills you go over north of Sunol, then it levels out at Pleasanton and the regen turns off. EGTs decay away, fuel gets well behaved. The stuff at the end is pulling off the freeway and a short drive into Danville for lunch at Armadillo *****'s BBQ. The last plateau in the fuel is idling writing the file and letting the EGTs drop a bit more. Truck was empty, cruise control set to 65 mph.

I also captured a bunch of other parameters but these were the most interesting. I may try this again with a flat freeway run, it would be interesting to compare that with one after done after the new PCM flash which is supposed to somehow change the regen cycle to be easier on the valves.

 

You are one sick puppy! Very cool, though ... great info for those of us who thrive on this stuff.

 

Thank for sharing.... It would be interesting to perform the same plot but at a steady speed/throttle position to eliminate some variables.

 

Good stuff SR!

Agreed... I have watched temp fluctuations in EGT14 swing up/down a couple hundred degrees even during steady state 65 mph (not towing)..
It would be really interesting to see steady state fuel flow and also oil temperatures. One other thing I would be curious to know is - what is EGR doing during a regen cycle?

 

I'll try to capture one during a flat freeway run, but of course you can't always arrange that.

The fuel flow is pretty flat line in steady freeway driving, but very twitchy during regen. It seems to have the same background flow but has pulses, usually several a second of up to 2 or 3x the background. Then they will stop for a second or two. I haven't noticed anything abnormal happening with oil temps but haven't paid much attention.

EGR is a little harder to understand. There are some PIDs but it isn't clear to me what they relate to. The DEF pump PWM is also a little hard to understand - it is twitchy all the time, and it isn't clear from watching it why it does what it does.

 

Great info and data. A log capture of the same route without the regen cycle would be interesting to see what the baseline data on looks like for that route.

 

I would really like to know the EGR strategy for diesels these days. I know and understand it well for gassers, but suspect that diesels would be a different animal since they don't use air volume as a means to control power.

 

That is awesome. Thanks for sharing. The engineer in me really appreciates this type of info.