Half Hour Long Regen Possible

Noticed a regen happening today. My wife stated she might have interrupted once or twice this week. So at our destination I left her in the car while I took care of business. 26 min later the car is still at 950 RPMs fans going. So I get back in a blip the throttle twice and RPMs go back to 800 like it is done. Sit a few min more for fans to go off.

Also notice what feels like driveline slack when pressing or releasing accelerator while in motion. It sounds like a soft knock sound and only occurs once per press or release. It can occur even with a very slight or hard press of the pedal.

Any ideas on either?

The idle won't go back to normal until you blip the throttle. It's possible that the regen could have finished several minutes before you tried that.

A ScanGauge (or whatever) would be a great gadget for your car. It sounds like both of you are interested in the vehicle's operation and it will take the guess work out of regen activity.

That said, I have noticed a very long (15+ minutes?) regen once on the highway (watching the ScanGauge)... Not sure why.

The regen didn't last that long, the ECU just doesn't lower the idle speed when it finished.

The only way to tell for sure is with something monitoring the EGTs.

-J

I have some general questions about regen cycles as well,

What are the visual/audible cues that the TDI is doing a regen?

Is there any way to monitor or initiate regeneration using VCDS?

I've noticed on a few occasions when I've shut down the engine, the radiator fan continues to run for several minutes. Did I just interrupt a regeneration cycle?

snow patrol said:

I have some general questions about regen cycles as well,

What are the visual/audible cues that the TDI is doing a regen?

Is there any way to monitor or initiate regeneration using VCDS?

I've noticed on a few occasions when I've shut down the engine, the radiator fan continues to run for several minutes. Did I just interrupt a regeneration cycle?

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Rpm's will climb to 1g

Not standard, but you can monitor with a gauge

yes, it does not matter, drive more worry less

snow patrol said:

I have some general questions about regen cycles as well,
What are the visual/audible cues that the TDI is doing a regen?

Click to expand...

Elevated idle, radiator fans running, 1000+ degree DPF temperature (easily monitored on a ScanGauge or similar device).

Is there any way to monitor or initiate regeneration using VCDS?

Click to expand...

There is an option to initiate a service regeneration if the soot loading in the DPF exceeds the maximum allowable amount for an automatic regeneration

I've noticed on a few occasions when I've shut down the engine, the radiator fan continues to run for several minutes. Did I just interrupt a regeneration cycle?

Click to expand...

Yes.

vwracer said:

Rpm's will climb to 1g

Not standard, but you can monitor with a gauge

yes, it does not matter, drive more worry less

Click to expand...

,...unless you think 1300f under your hood/floor, zero coolant/oil flowing, with only ambient air blowing by, isn't a good thing...

snow patrol said:

Did I just interrupt a regeneration cycle?

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VeeDubTDI said:

Yes.

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I disagree that all fan running conditions are indicative of regenerous interruptus. You could have interrupted a regen cycle, but I've observed that after a drive up a hill (like to home with the roads' climb in elevation) that coolant temps over 212-215 will keep the fans running for a few minutes after shutdown. I know that EGT's are low since I habitually allow it to idle to below 450F after parking based on my Scan Gage. But coolant temps are elevated, and the fans run to bring temps down. Of course the temp gage in the cluster is all but useless for actual temperature indication, which is why the SG is such an important tool for these cars.

I haven't nailed it down, but I think the fans will run any time the DPF temperature is above a certain point. Preliminary observations indicate somewhere in the 600-700F range. So if you shut it down after a long hill climb or otherwise high load driving, the fans will run even if it wasn't in a regen. Coolant temp could also play into the fan after-run strategy, as you mentioned.

There is no absolute indicator of a regen other than DPF temperature. When in doubt, monitor it so you know for sure. If you have any interest at all in your vehicle's operation, the ScanGauge is an essential tool.

tdiatlast said:

,...unless you think 1300f under your hood/floor, zero coolant/oil flowing, with only ambient air blowing by, isn't a good thing...

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VW obviously doesn't...

vwracer said:

VW obviously doesn't...

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...uhhh...and VW likes to sell, and service, their cars.

tdiatlast said:

...uhhh...and VW likes to sell, and service, their cars.

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With YOUR money!

VeeDubTDI said:

I haven't nailed it down, but I think the fans will run any time the DPF temperature is above a certain point. Preliminary observations indicate somewhere in the 600-700F range. So if you shut it down after a long hill climb or otherwise high load driving, the fans will run even if it wasn't in a regen. Coolant temp could also play into the fan after-run strategy, as you mentioned.

There is no absolute indicator of a regen other than DPF temperature. When in doubt, monitor it so you know for sure. If you have any interest at all in your vehicle's operation, the ScanGauge is an essential tool.

Click to expand...

Yes, I agree that exhaust temps also play a role in fan operations. But I see the EGT drop rapidly after a drive while waiting for temps to reduce to 450F before securing the engine. Coolant temps do not drop as quick due to heat soak from the engine and do not drop as fast as dpf temps.

kulak said:

Also notice what feels like driveline slack when pressing or releasing accelerator while in motion.

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No, but I do think I've noticed odd behaviour while a regen is occurring. An acceleration from a stop seems to require just a tad bit more pressure on the accelerator pedal on a manual as the clutch is released. First couple of times I inadvertently stalled while using accelerator pedal pressure that was just barely enough had a regen not been happening, but obviously was not enough during a regen. I first chalked this up to just having got back into a manual after many years, but then noticed it seemed to happen while the RPMs were elevated while idle at a traffic light. Maybe I'm wrong, but possibly a link?

I've since adjusted myself anyway so that it's no longer an issue.

One question about not interrupting regens after arriving to destination. I wait for the regen to stop before shutting off the car, but run the engine at 1500 rpm (in neutral) because I believe I'll be giving the DPF more oxygen and fuel to burn the sooth (like if I was driving instead of parked). Is that good or bad? Any opinions?

Not necessary. The computer regulates the air supply automatically so that it gets the proper amount of oxygen into and through the engine for the process to complete effectively.

Thanks VeeDubTDI!