[335D Alpha Pappa]

Yes another thread on DPF regen

A little background on DPF regens, not specific to BMW:


What is a Diesel Particulate Filter (DPF)

A DPF is a device designed and integrated into the Diesel Engine exhaust system to trap and remove Diesel Particulate Matter from the exhaust gasses of the diesel engine. Much like the Catalytic Converter on conventional petrol engines, the DPF works to remove harmful toxins and lower the emissions of your diesel engine making it more environmentally friendly.

The aim is to remove 80% in the average diesel particulate (matter) emissions and although a great concept, it brings about a whole new line of problems. We are taking calls constantly from anxious customers and garages across the country when their DPF light is illuminated on the dash, indicating that there is at least a partial blockage in the DPF system.

The problem with the DPF System

The DPF works to trap and remove diesel particulate matter from the exhaust gasses of the diesel engine before it exits the exhaust. This is removed into the atmosphere, simply removed from the gasses that flow through the exhaust to help lower emissions. Imagine, a DPF is like a honeycomb on the inside, similar to the Catalytic Converter (CAT) of a petrol engine. As the gasses flow through it, the DPF will trap the harmful diesel particulate matter and with it’s advanced technology break it down to remove as much of it as possible normally (between 80%-100%). The diesel particulate matter is burnt off at very high temperatures in the DPF and left behind is a very fine soot residue. The problem is this soot, it has no-where to go and so will then begin a blockage in the DPF system and this is how common DPF Problems occur.

The soot and matter will partially block your DPF causing the DPF light to illuminate on the dash (normally when 45% blockage is reached) at which point regeneration is required to get the DPF back in to it’s safety zone. Regeneration is the DPF’s way to clear the blockage through continuously burning it at higher temperatures and allowing the now harmless produce to escape through the exhaust system. There are two types of Regeneration processes which will be explained further below.

Sometimes the DPF light will appear on the dash intermittently, this does mean there is a partial blockage in your DPF and a regeneration process is required. You should make yourself aware of this process but many people are unsure or have no idea of this DPF system as it’s still very new and not explained to everyone. If you bought your vehicle from new at a dealership, then this would have most likely been explained at the point of sale but in the second hand car trade, you can’t expect this type of information to always be passed on.

What happens is drivers see the light, then see it go off and ignore it – not knowing it’s a partially blocked DPF. They continue to drive and again it will illuminate the DPF light on the dash and go off again but eventually it will stay on permanent and in most severe cases bring on the Engine management light and even the Coil Light which could start blinking. If this happens, you will lose all power and the vehicle will fall into “Limp home Mode”. This is the automatic reaction of the Engine Management ECU and if you’re at this stage then unfortunately it will be a costly repair. You could be looking at having to replace the DPF unit and having your Engine Management ECU reprogrammed.


Passive Regeneration?

Passive regeneration is an automatic regeneration which often occurs on drives where there is prolonged high exhaust temperatures like for example on motorway type runs, but it can’t be said that all cars get the required long journey motorway type trips necessary to complete a passive regeneration of the DPF system and so manufacturers have had to adapt the technology and designing an “active” regeneration process controlled by the Engine Management Computer also known as the Engine Control Module (ECM).

Active Regeneration?

When the diesel particulate (matter) loading in the DPF reaches a pre-set limit (normally around 50%), the ECU will make minor adjustments to the fuel injection timing system which will in turn increase the exhaust temperatures and help initiate the DPF regeneration process. This is a smart way of getting a motorway type temperature to build up inside the DPF system and begin a full regeneration to bring the unit back to good health, however, if the journey is a bit stop/start where you’re in a built up city with traffic then the chances are the regeneration will not complete and eventually the DPF light will illuminate on the dash to tell you that the DPF system is partially blocked.

At this point it is recommended that you try to find time to complete a full regeneration and this can be done on a simple 10 minute or so drive of speeds above 40mph.

If you do not do this and choose to ignore the light, it may go out but come back on and as you continue in a relatively slow, stop/start pattern of driving the diesel particulate matter loading will continue to build up and clog up the DPF system until it reaches closer to 75% blocked at which point you can expect other more serious warning lights to appear on the dashboard. By now, driving at speed alone will no longer be sufficient and the car will need to go to a garage or dealership for regeneration. The other lights may be the engine management light constantly on and possibly even the glow plug light blinking constantly. It is not advised to continue driving the vehicle under these conditions to avoid further costly damages to the DPF system and other mechanical components e.g Turbo and Engine.


DPF additives and how they work?

The most common type of DPF systems feature an in-built oxidising catalytic converter, which is located close to the engine where you will find the exhaust gases will still be relatively hot so that passive regeneration is possible. In some vehicles there’s not always space nearer the engine in which case some manufacturers use a different type of DPF system, one which relies on a fuel additive to lower the ignition temperatures of the diesel particulate matter particles so that the DPF can be located further away from the engine.

The DPF additive is usually stored in a separate tank and is automatically mixed in with the fuel when you go to fill up. Only very small amounts of the DPF additive are required for regeneration for example on average 1 litre of DPF additive would cover around 2800 litres of fuel, enough to cover 25,000 miles at 40mpg. With this type of DPF, regeneration would be initiated by the ECU roughly every 300 or so miles depending on the vehicle and will normally take 5-10 minutes to complete. Normally you won’t even notice this process taking place and if anything, once regeneration is completed you might see a glimpse of white smoke exit the exhaust and that’s it.

[335D Alpha Pappa]

IIRC from the advanced diesel document, the 335D regens happen every about 800 miles and the fuel tank has to be above a certain limit.

[DieselRacer]

Originally Posted by 335D Alpha Pappa

IIRC from the advanced diesel document, the 335D regens happen every about 800 miles and the fuel tank has to be above a certain limit.

Mine performs regens all the time with less than a quarter of a tank, I watch it with my tq app, and it happens well before 800 miles, I think city driving has something to do with that...

[GottaBeKD]

Originally Posted by 335D Alpha Pappa

IIRC from the advanced diesel document, the 335D regens happen every about 800 miles and the fuel tank has to be above a certain limit.

I recall 400 miles +/-was the magic number. Depending on load and driving conditions

[Puerto Rican 335d]

what regen oops I forgot I have a dpf deleted LOL anyway still waiting for my OBD II bluetooth amigos

[WreckerX5d]

Originally Posted by 335D Alpha Pappa

IIRC from the advanced diesel document, the 335D regens happen every about 800 miles and the fuel tank has to be above a certain limit.

I guess that's whats 'supposed' to happen. BMWhat said my regen has an average of 320miles.

[335ddd]

Originally Posted by Wrecker335d

I guess that's whats 'supposed' to happen. BMWhat said my regen has an average of 320miles.

My bmwhat says the same thing . Like 551km

[dixy2k]

I get my regens more often, by choice. 160-250 miles.
I'd rather run a clean DPF.

[335D Alpha Pappa]

Originally Posted by dixy2k

I get my regens more often, by choice. 160-250 miles.
I'd rather run a clean DPF.

Are you forcing it thru the BavTech tool or BMWhat?

[dixy2k]

It's coded in the flash I have.

[DieselRacer]

My car last night started a REGEN with only 30 miles left in the tank, I filled up and went for a drive to let it finish...

[Vreimann]

Originally Posted by 335D Alpha Pappa

Are you forcing it thru the BavTech tool or BMWhat?

Can you force a DPF regen with BMWhat?

[Yozh]

Originally Posted by Vreimann

Can you force a DPF regen with BMWhat?

Not yet, it's coming as one of the paid add-ons.

[Vreimann]

Originally Posted by Yozh

Not yet, it's coming as one of the paid add-ons.

Thanks Yozh. Will be happy to see that function. In winter is when the odd regen timing is always never ideal.