2011 Octavia vRS Diesel - Fan on when cold

[Paul Bennett]

Hello,

My '11 plate vRS TDI estate confused me this morning when I parked at work (~7 miles from home, -1.5'c) as the fan came on when I turned the ignition off (car was up to temp on arrival).

Likewise at lunchtime I did a short journey and the same thing happened.

 

Is this normal behaviour as in a year of owning it I haven't noticed it before now (although I remember a friend parking her A3 2.0Tdi next to mine a month or so back and that did the same).

 

It's not always doing really short journeys either.

 

Thanks in advance.

[CWARD]

It will be the DPF regen kicking in.

[Paul Bennett]

Twice within half a day?

 

Does it need an 'Italian tuneup'?

[CWARD]

Is your air con on as this can cause the main fan to run on until the condenser has cooled down but that is normally a summer issue when the ambient temperatures are high.

 

Twice in a day is unusual. 

Edited 26 January, 2017 by CWARD

[Paul Bennett]

Climate control is on yes.

 

So:

Yes after journey to work.

No after journey to lunch.

Yes after journey to lunch.

No after journey home.

 

It's done circa 115k miles and is getting used increasingly less for long journeys as we use the mini (stupid economy).

[Jevpls]

3 hours ago, Paul Bennett said:

Twice within half a day?

 

Does it need an 'Italian tuneup'?

 

If the regen was interrupted then it might happen again and again and again...until the warning starts flashing.

 

And - cars don't need that so called Italian tuning at all.

 

 

[Paul Bennett]

Are you saying there's no benefit to a dpf of running at higher revs for a prolonged period (even when you're usually only doing quite short journeys)?

[James@RRG_Skoda_Rochdale]

An Italian tune up is a euphemistic term for taking the car out and driving it to maximum engine revs in a different gears repeatedly - that is not beneficial for a DPF on the verge of being full. 

 

Driving the vehicle under increased load in the mid range for a prolonged period IS beneficial.

 

The DPF regenerates most efficiently in 5th gear (on a 6 speed box) at around 2000rpm, ideally driving up a slight inclination. A tank of premium diesel won't go amiss either.

[Paul Bennett]

Thanks. I'd always taken it as a short motorway run at high revs rather than just ragging it around...

 

I found a post detailing the dpf behaviour of a Yeti; I'm assuming the process is the same for the Octy. Reading about it, the regen will have been interrupted on my journey as I won't maintain the required criteria for long enough and I won't have triggered it in my run out at lunch.

 

I've got a fairly long run tomorrow evening so I'll aim for 2k rpm in 5th for a period.

[James@RRG_Skoda_Rochdale]

The problem with the high revs is it creates blow-by cooling of the DPF and to achieve maximum efficiency during regeneration it needs to be as hot as possible. Having lower engine speed still allows for normal driving and regen but doesn't cool it too much.

[Paul Bennett]

Informative thanks and where I live now (Clitheroe), you're reasonably local.

[James@RRG_Skoda_Rochdale]

Plenty of decent hills up that way too!