Whats it doing when the engine revs.stays at 1000 rpm

[fireman]

Diesel vrs. Just come off motorway after slow lazy drive home and as i pulled upto the lights on exit i noticed the engine revs stayed at 1000 and the stop start was disabled. Later on after driving through town the car returned to normal. Mate suggested it is doing exhaust regen. Is he correct as driving on motorway was probably right conditions to do it?

[0voyager0]

Dpf regeneration for sure. Unfortunately it's common.

[fireman]

So whats this thing where you sit on the motorway at 55mph and 2000 rpm to allow for it to do it from time to time

[James@RRG_Skoda_Rochdale]

Passive regens are carried out under driving conditions where the dpf can generate enough heat to burn off appropriate amounts of soot to keep the pressure stable. These go on unnoticed most of the time.

When it idles high when you come to a stop, often with the fans running (which may also run on with the engine off for up to 20 mins) and has no lights on the dash it's been carrying out an active regen cycle during driving that hasn't completed.

This is because the driving conditions for a passive regen have not been met.

If the DPF light comes it is advised that you to drive at 50mph in 5th gear on the motorway or similar, this aids the ecu in active regen mode. During active mode extra fuel is injected in the form of a 4th injection pulse, this extra fuel vastly increases the combustion temps by double or even triple what they would normally be, this helps burn of the excess carbon build up.

Worst case scenario being a forced regen, using diagnostic equipment as carried out by a dealer, this is where too many failed attempts to regen the dpf have been made and the ecu deems it unwise to continue.

There's also a service regen that is carried out using diag equipment. This can usually be carried out under any soot load.

Edited 1 May, 2016 by James@RRGRochdale

[GoneToBeemer]

So whats this thing where you sit on the motorway at 55mph and 2000 rpm to allow for it to do it from time to time

That's when you get the DPF light when the car hasn't been able to complete a passive regen. You then have to drive the car under certain conditions to ensure it can clear the DPF.

[fireman]

So as i best to drive it under conditions that mean it can do a active regen if needed from time to time as also do fair bit of town driving daily?

[themanwithnoaim]

Rag it in low gears if you wanna avoid active regens, motorways cool the exhaust too much, needs heat I'm afraid

[fireman]

Ok chaps. Thanks again for your advice

[James@RRG_Skoda_Rochdale]

ragging it is what creates the solid carbon particulate build up.

To raise up exhaust temps effectively driving in a lower gear uphill is bar far the best technique to burn off excess particulates.

it's the increased engine load that helps clear the exhaust not raised engine speed.

Edited 30 April, 2016 by James@RRGRochdale

[MrAdamwood]

When it idles high and has no lights on the dash that's known as a passive regen.

When you have to drive at 50mph in 5th gear on the motorway or similar that's an active regen.

Worst case scenario being a forced regen, using diagnostic equipment as carried out by a dealer.

Sorry that's not quite right....

When you drive it fast with high revs getting the exhaust nice and hot it is passively regerating, burning a little soot all the time it's hot enough.

When it idles high at 1000 rpm, the a soot threshold has been reached and the car has interviened and is taking action by adding more fuel to create the high exhaust temps required to burn off a large quantity of soot asap, this is active regen.

When the dpf light comes on, this is telling you it needs a customer regen, it needs help as it has tried to carry out as many active regents as it can but the driving style has not allowed it to happen by driving short trips with low speeds...the light is telling you It needs to be driven in a certain way, higher engine speeds to carry out a successful regen..... If this is ignored it will go in to limp mode to protect itself and your off to the dealer....if you still carry on driving it, it's new dpf time!

[Auric Goldfinger]

You can do many miles at Motorway speeds and then get a regen within a few miles of home. This is because driving at motorway speeds in 6th ( Manual box ) the draft under the car keeps everything cool, once you leave the motorway and start driving a bit slower in differant gears the engine warms up enough to do a regen.

 

I drove home from N Wales last weekend and the car did a regen 5 miles from home.

[fireman]

Very informative info chaps. I'll adopt my driving style accordingly when in no rush to get home some days

[James@RRG_Skoda_Rochdale]

Sorry that's not quite right....

When you drive it fast with high revs getting the exhaust nice and hot it is passively regerating, burning a little soot all the time it's hot enough.

When it idles high at 1000 rpm, the a soot threshold has been reached and the car has interviened and is taking action by adding more fuel to create the high exhaust temps required to burn off a large quantity of soot asap, this is active regen.

When the dpf light comes on, this is telling you it needs a customer regen, it needs help as it has tried to carry out as many active regents as it can but the driving style has not allowed it to happen by driving short trips with low speeds...the light is telling you It needs to be driven in a certain way, higher engine speeds to carry out a successful regen..... If this is ignored it will go in to limp mode to protect itself and your off to the dealer....if you still carry on driving it, it's new dpf time!

I've amended my originally vague post to include more info.

higher engine speeds are not necessarily key to a successful regen though. Engine load is what creates more heat due to increased injection periods, that's why it's advised that you do 50 mph in 5th and not 70 mph in 3rd. But the main factor is that active mode is, well actually active. It'll take over the fuelling control itself and fire the extra fuel needed for the regen to take place.

[SuperbTWM]

higher engine speeds are not necessarily key to a successful regen though. Engine load is what creates more heat due to increased injection periods, that's why it's advised that you do 50 mph in 5th and not 70 mph in 3rd. But the main factor is that active mode is, well actually active. It'll take over the fuelling control itself and fire the extra fuel needed for the regen to take place.

 

I wonder if there is actually any actual data regarding what speed and gear is best for greater DPF temps. 

 

Some are saying that higher speeds cool the DPF because of the drafts caused, but surely travelling faster does increase engine load as well so there must be a balance somewhere. In my head doing 50mph in 5th isn't ideal as personally I don't think the engine is working hard enough and despite the cooling effect of the air I find it hard to believe the DPF is hotter at 50 in 5th than doing 80 in 6th. Just my opinion of course.

[James@RRG_Skoda_Rochdale]

Its in the owners manual (page 38/39) and how we've been told to carry them out by VW AG technical since the days of the mk2 vrs tdi circa 2006.

I assume that at this constant vehicle and engine speed combination the dpf is not cooled too much by the passing gasses and the additional fuel can be added and the ecu still keep engine temps within a safe spectrum, ideally travelling up a slight incline would cause the need for more power thus helping the situation.

Again just because the vehicle speed is higher it doesn't mean the engine is under most load.

Mid range is where the engine is under most load and is the point from where most power is produced.

When power is measured on a dyno the vehicle is driven to maximum rpm in the middle gears such as 3rd 4th and 5th because the highest gear is only geared to produce higher top end speed and not acceleration due to the nature of its design where the mid range gears are of a similar size to each other they give a better relative measurement because they are closer to a 1:1 ratio.

If you think about it doing 2500rpm in 5th is right on the edge of the power band and keeping the engine under load, the engine is propelling the car and loading the gearbox. where doing 80mph in 6th is cruising speed where the vehicle is running off its own momentum, the gear is designed to maintain top vehicle speed with minimal engine load so it might only be running at 1500rpm.

Edited 1 May, 2016 by James@RRGRochdale

[davitc]

Checkout a few posts on here i.e.

 

http://www.briskoda.net/forums/topic/301020-my-new-diesel-smells-like-burning-rubber-andor-the-fan-stays-on-after-engine-is-turned-off/

 

I typically get this after a short spirited drive on a Motorway and with my shortish (20 mile) Commute I'm getting down to 1 active regen a tank full of fuel now I've a few miles.

 

Take action if you get the DPF warning light as others have said, otherwise jus let it do it's thing.

Edited 1 May, 2016 by davitc

[Gabbo]

Very informative info chaps. I'll adopt my driving style accordingly when in no rush to get home some days

 

No need to adapt your driving style or drive round for 15minutes with high rpm, you are just wasting your fuel & time for no reason.

What has occured is perfectly normal & in no way a problem.

 

When the car starts a regeneration it has no way of knowing if you are 30s or 5hours away from your destination.

Sometimes you will stop before its able to fully finish & will notice high-idle & sometimes loud fan noises after you stop.

This is perfectly normal & nothing to worry about at all.

It will continue (if needed) the next time you drive the car.

 

Unless you have a warning light on the Dashboard (and I can't remember anyone on the forum reporting this with the O3) just carry-on driving as normal.

[Gadget007]

in my Vrs i have found that it on average does an active regen per each tank full (850km + on average for each tank).

using an OBD scanner and the torque app on my phone the exhaust temperature normally sits around 350degC when driving and around 200 when idling. during an active regen at 110km/hr temp raises to 650ish, dropping the car back a gear or two raises the temp to 700 with no noticable change in fuel consumption (based on instantaneous consumption reading) and at this temp the regen lasts for a shorter period.

 

from my experience if i regularly take a drive on the highway with the revs above 2k regenerations seem to occur less frequently.

[frdazzvrs]

I have a skoda octavia tdi vrs 170 bhp mk2 and recently i had a remap stage 1 and now I am experiencing the same problem and my mechanic change the manifold and the air intake and now the solenoid valve and still the car revs 1000rpm from time to time and i am reading the comments here and it's seems to be normal to do so.  I have only one question when it is doing the 1000rpm rev it is normal that the car work a little bit different like when you press all the gas paddle it's like choking for a split of a second and then it goes again. And when i am on 4th gear and i press all the paddle down instantly when it reaches 130 km it's start to take and lose power instantly and if i press the paddle slow it's ok