Regen cycles? I have heard of them, but not witnessed any yet?

Hey guys,

I have driven my Golf-TDI close to 2k miles now and have yet to witness a regen cycle.

What are the signs, clues that you can give me so that I am aware of when the regen cycles are occurring?

Thanks so much!

fans running, funky smell, lowerOOPS! higher idle when stopped.

Throwback7r said:

fans running, funky smell, lower idle when stopped.

Click to expand...

Reverse this ... the engine will idle *faster* than normal when stopped (about 1000rpm rather than the normal 900rpm).

I normally detect a very slight hiccup when the regen starts, but didn't associate it with a regen for at least a few thousand miles and a number of cycles.

Thanks guys, so it seems VW does not necessarily want you to be aware of the regen cycles. I did park the car once and the fan kept running, I assume that was a regen?

One of my friends with a MKIV Golf TDI mentioned he get's a light in the console when the regen occurs. Is there such a thing for our MKVI?

I don't think a MK4 would have a DPF to regen with...

When the car is happiest (warm, etc) it idles right about 800rpm, or 830*. Regens put mine at ~950. If it is too cold (excessive idling below freezing temps for example) it idles around 980. It runs ~890 when warming up in warm (over 40F) temps. (Torque app observations over 60k miles)

*I'm guessing this 30rpm differnence is related to some EGR valve opening or something

Also, I'd think regens would be more noticable with a manual than DSG...but otherwise I agree, you can feel the hiccup when it kicks in and mines acts a little rough at idle sometimes, so I certainly notice them. The fuel flow rate at idle nearly doubles also.

Of course, all this is my 2011 Jetta experience...

VW has gone to great lengths to hide our car's "dieselness". Your car has regenerated many times already, you just didn't notice it.

If you are doing primarily highway driving most of your regenerations will be of the "passive" type and you will notice nothing unless you have an EGT gauge. Active regenerations occur as necessary based on time, soot load, DPF pressure differentials, etc. These "active" regenerations are easier to notice. Idle speed goes up a bit, radiator fans run at full speed, and you will sometimes notice a "burning brakes" like smell. Regenerations are most commonly noticed when you turn off your engine while a regeneration is in progress. In this case your fans will continue to race for 5 to 10 minutes after you turn off the engine.

The OP can rest assured that DPF regenerations have been occurring. If not, you would have had problems by now. There is no light or other indication in the instrument cluster to tell you that a regen is under way. The only light related to the DPF is a warning light when it is getting clogged and attempts to regenerate have failed. This light only lights when there is a serious problem. It does not turn on at all if everything is working properly.

Have Fun!

Don

P.S. Dozenspeed is correct. A Mk4 does not have a DPF. Therefore it does not have DPF regenerations and it has no light to indicate this. In North America DPF equipped cars started with the 2009 model year (late Mk5s).

In 2000 miles your car should have performed about 5 or 6 regens. Best way to monitor is by watching EGT (exhaust gas temp) on a ScanGauge or equivalent OBD2 data reader.

Thanks to everyone for the informative responses. I really do appreciate you all taking the time to educate a newcomer to the TDI scene.

http://www.myturbodiesel.com/wiki/tdi-dpf-faq-repair-cleaning-and-pictures/

Some good reading on DPF regens.

Connect a scangauge, put in the coding to monitor EGTs and DPF temps, watch the numbers rise!

unpleasant smell, (not the sickish sweet normal idle smell, more like burning plastic) rough running, fan stays on when stopped, poor economy (like -10%). If you don't make short trips or let it idle often, and occasionally beat the bag out of it most of your regens will be passive, ie naturally occurring high egt's clean the dpf, not ecu forced conditions (fuel injected on the exhaust stroke). Got a 10 minute uphill section of highway you can run at 80+ mph?

A bit of spirited driving really helps this engine, the Italian tuneup so to speak. Might also help with the intercooler icing issue by sucking any moisture out before it has a chance to build up to unsafe levels.

The ECU will do an active regen approximately once every 500 miles regardless of driving style. You may get more depending on driving style, but never less.

The rad fans running after you shut the engine off doesn't always indicate a DPF regen, does it?

Reason I mention is, my gasser MK2, MK5 & my old W123 Benz used to do that just to cool the engine off after a certain amount of time. I always thought it was a Euro thing to program the after run fans...

Diesels rarely generate enough heat to require the fans to run after shut down. The only time my wagon has done this is after a 30 minute track session where I'm running the engine between 3500-5500 RPM in 3rd and 4th with my foot flat on the floor when I'm not braking for the next turn. Coolant will get up to 95C, and the fans come on at around 98C. After some sessions the fans would run on low, but that's it. Gassers are different, of course.

Now that I can see EGTs it's interesting to see how much is going on regarding regens. My question is where does the heat come from, the fuel being pushed downstream? If so why would unburned fuel passing through the turbo raise EGTs?

It's coming from post injections, but it isn't like there's 100% raw fuel coming through the turbo. Most of that fuel starts to burn on its way through, raising the EGTs. Also, the exhaust throttles will modulate to create more backpressure and restrict flow through the DPF, which fuels the fire, further increasing DPF temps. This is why the DPF can remain at 1100F even when the pre-turbo EGTs are around 850 when the engine is idling during a regen.