T6 Hovercraft mode - what is actually happening?

[2into1]

We get plenty of threads asking why T6s often imitate a 'hovercraft' when you stop and park up. We know it happens when you stop the engine part way through a DPF regeneration.
But do we know what is actually happening when all those fans are whirring and heat blasting from underneath?
Is it using fuel as I wander off with the keys in my pocket?
Is it just using 12v to power the fans to cool down the process that was already underway?
- am I doing 'harm / wear' each time it happens?

I'm particularly annoyed that the 2(?) hourly forced regeneration always seems to having terrible timing. Today it again chose to start a regen just as I returned from a long run. It did its hovercraft impression as I nipped into Tesco before arriving home. It did it again as I arrived home. It will do it again tomorrow when I drive 4 miles to yoga, and probably again as I return.
I'll then be back to longer drives, free from re gens as it waits until I'm a mile away from home to start the next one.
I read that some users leave the engine running to allow it to finish the cycle, or drive a few extra miles to achieve the same - which rather negates the environmental goals of the system.
I think the more we know about the process, the better we can 'manage' it.
- so what is happening?
- how long does it take?
- does that timing depend on how its being driven?
- how long is it between regens?
- is that fixed or does better trips lengthen the intervals?

 

[Jay20cali]

Great post

 

[Jay20cali]

Noticed this a few times with a weird smell had me worried for a min??
now I know it’s standard,
but I would not expect it on a nearly new van with super low miles and only motorway trips under its belt

 

[Billywizz]

It’s doing its bit to pretend he/she is environmentally friendly when it’s not!
Just enjoy and drive and sleep in it before you’re not allowed to.

 

[VW Guru]

We get plenty of threads asking why T6s often imitate a 'hovercraft' when you stop and park up. We know it happens when you stop the engine part way through a DPF regeneration.
But do we know what is actually happening when all those fans are whirring and heat blasting from underneath?
Is it using fuel as I wander off with the keys in my pocket?
Is it just using 12v to power the fans to cool down the process that was already underway?
- am I doing 'harm / wear' each time it happens?

I'm particularly annoyed that the 2(?) hourly forced regeneration always seems to having terrible timing. Today it again chose to start a regen just as I returned from a long run. It did its hovercraft impression as I nipped into Tesco before arriving home. It did it again as I arrived home. It will do it again tomorrow when I drive 4 miles to yoga, and probably again as I return.
I'll then be back to longer drives, free from re gens as it waits until I'm a mile away from home to start the next one.
I read that some users leave the engine running to allow it to finish the cycle, or drive a few extra miles to achieve the same - which rather negates the environmental goals of the system.
I think the more we know about the process, the better we can 'manage' it.
- so what is happening?
- how long does it take?
- does that timing depend on how its being driven?
- how long is it between regens?
- is that fixed or does better trips lengthen the intervals?

Hi @2into1 allow me to answer your questions

1 what is happening well the cooling fans are running to cool down the engine bay when your moving air is being rammed into and over the engine, when you stop so does the air flow so the fans run at full speed to cool down the exhaust and engine. Parts of the exhaust system get to over 800 degrees when in regen and the cooling fans run to stop a thermal incident happening. They can run for up to 10 mins after engine off. It’s only the fans nothing else is consumed.

2- how long does it take? This is variable depending on your driving style optimum conditions for regen are 2000rpm in 4-5 gear it then takes around 15mins but it all depends on the driving style of the driver and condition it’s used in i.e town low revs it will take longer to regen than motorway speeds.


3 does that timing depend on how its being driven? As answerd in the last question yes


4 how long is it between regens? Totally variable depending on the conditions it’s operated under I.e constant town work = higher regen frequency motorway work = lower frequency but it will always go into regen every 2 hours of a drive cycle accumulatively I.e 30mins driving day 1 30mins day 2 1 hour day 3 and it will go into regen

4 is that fixed or does better trips lengthen the intervals? The 2 hour cycle is fixed but it’s variable depending on operating conditions, driver and journey type ie town or motorway.

Hope that makes it a little clearer but if not please ask as many questions as you want one final point always have over a quarter of a tank of fuel if just running around town or the vehicle will not regen and you will go into limp mode and ha e to go to a dealer

 

[Tom Rae]

........................................................
Hope that makes it a little clearer but if not please ask as many questions as you want one final point always have over a quarter of a tank of fuel if just running around town or the vehicle will not regen and you will go into limp mode and ha e to go to a dealer

That is a bit concerning as quite a bit of my mileage is around town. No mention of that anywhere else that I have found? Thanks for the heads up.

Tom

 

[Volkywagen]

it would be interesting to see what the urban MPG figures are with the regen constantly working

 

[Loz]

it would be interesting to see what the urban MPG figures are with the regen constantly working

24-27 welcome to my world...)

 

[zinglefiffy]

It's a shame there isn't a button or some way of telling the van it's a good time to get its next regen in if its close to needing one.

Sent from my Nokia 6.1 using Tapatalk

 

[Lightning]

24-27 welcome to my world...)

My petrol Cali is more efficient than that.


Sent from my iPhone using Tapatalk

 

[Les]

Hi @2into1 allow me to answer your questions

1 what is happening well the cooling fans are running to cool down the engine bay when your moving air is being rammed into and over the engine, when you stop so does the air flow so the fans run at full speed to cool down the exhaust and engine. Parts of the exhaust system get to over 800 degrees when in regen and the cooling fans run to stop a thermal incident happening. They can run for up to 10 mins after engine off. It’s only the fans nothing else is consumed.

2- how long does it take? This is variable depending on your driving style optimum conditions for regen are 2000rpm in 4-5 gear it then takes around 15mins but it all depends on the driving style of the driver and condition it’s used in i.e town low revs it will take longer to regen than motorway speeds.


3 does that timing depend on how its being driven? As answerd in the last question yes


4 how long is it between regens? Totally variable depending on the conditions it’s operated under I.e constant town work = higher regen frequency motorway work = lower frequency but it will always go into regen every 2 hours of a drive cycle accumulatively I.e 30mins driving day 1 30mins day 2 1 hour day 3 and it will go into regen

4 is that fixed or does better trips lengthen the intervals? The 2 hour cycle is fixed but it’s variable depending on operating conditions, driver and journey type ie town or motorway.

Hope that makes it a little clearer but if not please ask as many questions as you want one final point always have over a quarter of a tank of fuel if just running around town or the vehicle will not regen and you will go into limp mode and ha e to go to a dealer

Hi when you say it's fixed 2hrs but variable is that 2hrs or less between regens never more than 2hrs.

 

[Lightning]

Actually, I just checked and my long term average TSI consumption on the trip computer is 23.1, so you’re still winning.


Sent from my iPhone using Tapatalk

 

[Volkywagen]

My petrol Cali is more efficient than that.


Sent from my iPhone using Tapatalk

so was my dads 2.8 brooklands!!

 

[motacyclist]

It's a shame there isn't a button or some way of telling the van it's a good time to get its next regen in if its close to needing one.

Sent from my Nokia 6.1 using Tapatalk

Good idea, like choosing when your computer does an update

 

[alan middleton]

Actually, I just checked and my long term average TSI consumption on the trip computer is 23.1, so you’re still winning.


Sent from my iPhone using Tapatalk

. My mustang does more than that!

 

[B J G]

Actually, I just checked and my long term average TSI consumption on the trip computer is 23.1, so you’re still winning.


Sent from my iPhone using Tapatalk

Mine does about 27 during regen but about 35 at other times giving an average of 33. Well over a TSi 23.

 

[Lightning]

Mine does about 27 during regen but about 35 at other times giving an average of 33. Well over a TSi 23.

On the bright side, petrol is cheaper, I’ll never have a DPF light, I won’t run out of AdBlue or over fill it, or have to drive around with more than 1/4 of a tank to avoid a dealer visit, and Euro 4 petrol is still allowed in the London ULEZ, so mine is likely to be useful for longer On top of all this I don’t sound like a hovercraft or get oily hands every time I fill up, which is often...

I wouldn’t swap.


Sent from my iPhone using Tapatalk

 

[westfalia]

On the bright side, petrol is cheaper,

Petrol is 20 cents per litre more than diesel here in germany.

 

[Lightning]

Petrol is 20 cents per litre more than diesel here in germany.

Thanks, I won’t be going there then! It seems to vary a lot throughout Europe, when I was in Portugal there was a diesel shortage.


Sent from my iPhone using Tapatalk

 

[VW Guru]

Good idea, like choosing when your computer does an update

The new model year crafter will actually have a button on the dash to initiate a regen because crafter size vehicles do a lot of start stop work with couriers. Not sure if they will bring the idea over to Cali/ transporter but there is no reason why not as they have the same engines

 

[B J G]

On the bright side, petrol is cheaper, I’ll never have a DPF light, I won’t run out of AdBlue or over fill it, or have to drive around with more than 1/4 of a tank to avoid a dealer visit, and Euro 4 petrol is still allowed in the London ULEZ, so mine is likely to be useful for longer On top of all this I don’t sound like a hovercraft or get oily hands every time I fill up, which is often...

I wouldn’t swap.


Sent from my iPhone using Tapatalk

I spend approx. 3 months per year in France where diesel is cheaper than petrol. Only takes a Budget to revert the petrol price advantage. As far as I'm aware ULEZ applies to Euro 4 diesel same as petrol plus it will be safe to assume that all versions of internal combustion engined vehicles will have the same end of use due to emission/clean air legislation.

 

[Lightning]

I spend approx. 3 months per year in France where diesel is cheaper than petrol. Only takes a Budget to revert the petrol price advantage. As far as I'm aware ULEZ applies to Euro 4 diesel same as petrol plus it will be safe to assume that all versions of internal combustion engined vehicles will have the same end of use due to emission/clean air legislation.

ULEZ applies to Euro 6 diesel.
So you spend 9 months in U.K. where petrol cheaper.



Sent from my iPhone using Tapatalk

 

[Digger]

ULEZ applies to Euro 6 diesel.
So you spend 9 months in U.K. where petrol cheaper.



Sent from my iPhone using Tapatalk

Euro6 vehicles exempt under ULEZ

 

[Lightning]

Euro6 vehicles exempt under ULEZ

Euro 6 diesel exempt and Euro4 petro exempt


Sent from my iPhone using Tapatalk

 

[B J G]

ULEZ applies to Euro 6 diesel.
So you spend 9 months in U.K. where petrol cheaper.



Sent from my iPhone using Tapatalk

Wife's car was changed from a diesel to a petrol. She hates the smell of petrol. Mainly used for local runs.
Actual cost difference on my modest mileage between petrol & diesel isn't a worrying cost factor.
I'm happy with diesel as the best option for my use with its torque and bhp.