Fan Issues

[Stripey]

Oh, and forgot to add, the high speed fans that occasionaly stay on when you turn ignition off just means you have interrupted an active regen or one has recently completed. The fans are on to cool the various bits down as the regen makes things very hot. So the fans are not a regen in progress as I previously thought!

Also, it is not dangerous or damaging to interrupt a regen. It should start again when the car is next started as the sensor would still be picking up high soot levels in the DPF.

 

[jivemonkey2000]

If a passive regen is occuring and you interrupt it, will this not result in the fan being activated on park and remain on also? I ask as today mine was up to 103 degrees on the MFD for oil temp and around 8 minutes later I arrived at work - the fan stayed on. I was aware this was related to the regen, but are you saying that this would be an active regen and not passive?

 

[Stripey]

I dont think oil temperature is relevant, its all about exhaust temp which isnt displayed anywhere.

You cant really 'interrupt' a passive regen as such because a passive regen is just the natural heat from normal driving, burning off the soot. Effectively, this is the filter working as it should. So in your example, i would guess that the fans were on to cool stuff down because of an active regen (i.e. more fuel being burnt to produce hotter gases). As that fuel burn is done in the engine, the fans need to cool it down. With passive, certain driving styles (higher revs) produces hotter gases naturally so they burn the soot without extra help.

 

[jivemonkey2000]

I dont think oil temperature is relevant, its all about exhaust temp which isnt displayed anywhere.

You cant really 'interrupt' a passive regen as such because a passive regen is just the natural heat from normal driving, burning off the soot. Effectively, this is the filter working as it should. So in your example, i would guess that the fans were on to cool stuff down because of an active regen (i.e. more fuel being burnt to produce hotter gases). As that fuel burn is done in the engine, the fans need to cool it down. With passive, certain driving styles (higher revs) produces hotter gases naturally so they burn the soot without extra help.

Would it not be too much to assume that if the engine is running @ 100 degrees, then it's more than likely the exhaust temperature would be up there with regards temp too? Might see if I can log them on VCDS on my next journey to see the relationship..a nice graph would be great!

 

[matt2]

I found a copy of the VW service training manual for mechanics/technicians (for tdi common rail engines) on the internet. It goes into detail about the DPF which was interesting to read.
........

You may find this link useful: http://www.vwaudiforum.co.uk/forum/showthread.php?147028-DPF-information

 

[Stripey]

Would it not be too much to assume that if the engine is running @ 100 degrees, then it's more than likely the exhaust temperature would be up there with regards temp too? Might see if I can log them on VCDS on my next journey to see the relationship..a nice graph would be great!

I'm far from being a mechanical expert (so I could be talking utter nonsense) but I wouldn't expect much of a relationship between oil temp vs exhaust temp once an engine gets up to 'normal' running temperature. This is because an engine is cooled to keep it at (or below) a certain temperature but exhausts/gases are not cooled and vary according to how hard the engine is being worked.

Mechanics, please step in and give the definitive answer!

 

[Option155]

This is the reason I went from MK5 Diesel to MK7 Petrol. Too many low mile journeys and clog up issues after 30K miles. I''m pretty sure I must have been asked about typical driving (annual miles, typical journey etc) which would have flagged up that Diesel not appropriate, but was definitely not advised against. Great car, but expensive problem a few years down the line. Glad no such problems poss now.

 

[dickt]

Mine does active regens whenever it feels like it. I've learnt to ignore them - both the stationary rpm and the fan noise after stopping.
Maybe you should not have been sold a diesel?
An earlier member of this forum got VW and his dealer to admit that he was mis-sold the diesel.

 

[grahamgolf]

According to the handbook the gear change indicator on my (2.0 TDi manual) will suggest a lower gear to aid regeneration (it doesn't say if this is active or passive).

I do relatively few short journeys. The sales guy on handover pointed out that driving in 6th (at least at legal motorway speeds on the flat roads of southern Britain) will not get the exhaust gasses hot enough to do any regeneration. He suggested changing down to get the revs above 2,500 for 10 mins occasionally. Only done 400 miles in 6 journeys and not aware of a regen yet.

As an aside, is there any evidence that premium diesel slows down the soot build up in the DPF?

 

[jivemonkey2000]

Mine does active regens whenever it feels like it. I've learnt to ignore them - both the stationary rpm and the fan noise after stopping.
Maybe you should not have been sold a diesel?
An earlier member of this forum got VW and his dealer to admit that he was mis-sold the diesel.

I am fully aware of a diesel's DPF requirements and did not get "advised" by a some sales boy I needed otherwise, I knew that my driving patterns needed a diesel, which is why I ordered a GTD instead of GTI; salesmen know shit all. Regarding your regens..it sounds like you should not have been sold a diesel. People should educate themselves prior to purchasing a new vehicle. I was only reaching out to other person's experience as I drive shorter distances during the week and was curious as to the regen operation.

 

[tom1]

I found a copy of the VW service training manual for mechanics/technicians (for tdi common rail engines) on the internet. It goes into detail about the DPF which was interesting to read.

To summarise:

The regen of the DPF is performed in stages:
- warm up
- passive regen
- active regen
- customer initiated regen drive
- service regen

Warm up - this brings the oxidation catalyst and DPF up to operating temperature quickly through an extra injection of fuel after the main injection. Phase is complete when operating temperature is reached.

Passive - soot is continuously burnt without additional intervention when exhaust temperatures range from 350 - 500 degrees C. This is often at normal motorway/A road driving conditions.

Active - when exhaust temperatures are not high enough to effectively burn off soot particles, soot accumulates in the filter. When a specific soot load has been reached, the engine control module will initiate an active regen. Effectively similar process to warm up phase - more fuel burnt to increase exhaust temperature.

Customer initiated - lots of short journeys, where high enough exhaust temperatures are not reached, will cause the filter to reach threshold value. The DPF indicator lamp will come on in the instrument panel. This prompts the driver to perform a regen drive - a short journey at increased speed to ensure high enough exhaust temperatures are reached to burn off the soot in the filter.

Service - if the regen drive is not performed (or successful) the DPF lamp and the glow plug indicator lamp will appear in the instrument panel simultaneously. The text 'check engine - service shop' will also appear. This prompts the driver to take the car to a garage to get it sorted.

There is also a 'Distance Regen' which is a distant dependent regen. The engine control module will initiate an active regen automatically if during the last 466 - 621 miles (750 - 1000 km) no successful regen has taken place. This is an additional safeguard to minimise load condition of the DPF.

It seems there is no visible indication (icon/message) that a regen is taking place, only an indication that one needs to take place. As we all know, there is an audiable indication (the fan running) and a smelly indication (soot burning) but if you're driving, the only indication that a regen is taking place is slightly higher revs at idle.

(I can't guarantee the above info is totally up to date and accurate but it has gone some way to improving my understanding!)

There are 2 more things to look out for that I have noticed (1.6L TDI)

While in regen mode you will get much more turbo spool, this is to do with the engine getting slightly more power, or something along those lines I was told.

The Current MPG will normally flick to 200mpg if you're on a flat/down hill surface and take your foot off the gass, while in regen mode this will go up in blocks for example 60, 80, 120, 160, 190, 200. Rather than 60, 200

 

[buu]

I have 1.6TDI with 7 speed DSG. If I understand correctly from the manual if you have a DSG then the regeneration icon light will not glow at all? So the regeneration happens automatically no matter how you driver and where you drive (city traffic/motorway)?
I noticed that regeneration starts when at idle with the auto hold on the idle RPM is not approx 800 but approx 1000.
Question: if the regeneration is happening when I reach home and still continues should I leave the engine running for some 5-10 minutes in P gear till the regeneration end or just turn off the engine.

Yes, I can confirm when the regeneration is happening the acceleration is much better, especially when the car is stopped at the junction.

 

[Stripey]

Question: if the regeneration is happening when I reach home and still continues should I leave the engine running for some 5-10 minutes in P gear till the regeneration end or just turn off the engine..

Might as well just turn engine off. It will start another active regen when you next drive it.

 

[Lenti]

HI Guys,
I have the 1.6 TDI BMT, i have recently noticed this like i can say for a week, when i start the needle stays in 1000RPM, and while i drive to work and stop for a coffee i see the needle than drops a little bit but not as it should be as standard at 800 or 900RPM, i turn it off have the coffee and when i start again it stays at 800RPM appr...so just curious if this is the regen of particel filter taking place or not, as i am reading this thread it seems so but do we have the confirmation. And by the way i drive like 40 km/h up to 100km/h but this 100km/h not very often.

 

[bertj]

I don't know if this makes sense but I suspect that constant driving in Eco mode complete with stop/start will produce lower engine/exhaust temperatures, increased soot and therefore more frequent regenerations. I've had quite a lot of experience with the somewhat 'gutless' 1.6tdi engine fitted to a dsg car and found that it seems, IMO, to struggle at low revs when the dsg box automatically selects a higher gear; Eco mode only makes this characteristic worse. Rather beside the point but I also find the selection of coasting in Eco mode very disconcerting because I miss the normal engine braking. I'm also quite surprised that the OP finds a significant difference in fuel consumption when using Eco mode.