DPF Musings (Mostly P3)

My friend Nathan Rich posted some really useful stuff about DPF’s and regens over on the Volvo V70 & XC70 P3 owners club facebook page. There have been a few times reading other posts i thought, man, more people could do with reading that post……I’ll ask Nathan if i can put it on the blog, and he said “of course!” (actually he said “Yeah crack on mate”).

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So here goes

“As promised for those of you that were interested, a boring, dull and pointless if you just remove and remap, analysis of DPF regeneration.

FAIR WARNING! it’s quite a long one. If it’s not for you then scroll on. I’m just trying to be helpful and contribute to the group. It took a long time to compile, research and write out. This was initially for my own consumption but I hope it stops some of the myths and nonsense advice from people with perhaps good intentions but no clue.

I mentioned that these results came from a 2011 V70 D5 Twin turbo 205ps. I have had similar results from a 2015 XC70 D5 215ps but there are some small differences between the two. AWD models (so XC70s mainly) have a catalytic converter with a separate DPF whilst the V70 has a combined cat and dpf off the back of the turbo, to my understanding.

From VIDA:

For the particle filter to be regenerated, an exhaust temperature of approximately 600 °C is required downstream of the filter. This is achieved via various engine operations, such as throttling, changed fuel injection, glow plug activation.

Regeneration can be triggered in a number of ways:

▪ Used fuel volume,

▪ Time that engine has been running.

▪ Distance driven since last regeneration.

▪ Differential pressure across the particle filter or calculated particle weight in the filter.

▪ Start in the workshop using the diagnostic tool.

▪ Particle level in the filter calculated by the engine control module (ECM)

I was able to find this information. There are five levels or circumstances in relation to the DPF based on the calculated weight of soot in the filter.

Level 1 (24 grams): Engine control module (ECM) starts combustion of soot particles in the particle filter during highway driving.

Level 2: (27 grams) Engine control module (ECM) starts combustion of soot particles in the particle filter during normal driving.

Level 3 (32 grams): A text message, Soot filter full, is sent to the Driver information module (DIM), and the control module sets a DTC.

Level 4 (36 grams): Engine control module (ECM) can no longer start combustion of soot particles of its own initiative. A further text message, Engine system service required, is sent to the Driver Information Module (DIM), and another fault code is sent.

Level 5: (100 grams of soot or more) Combustion of soot particles cannot be started using the diagnostic tool.

I discovered that in order for a regeneration to take place you need:

-Minimum 20 litres in the fuel tank.

-No outstanding major faults.

-Of course the car must be at operating temperature.

If you want to know when your car is regenerating then you can try and notice the drop in fuel economy but this is harder than you think unless you are on a relatively smooth piece of motorway, or if you have an OBD2 dongle (I recommend a semi decent one like Veepeak) use Car Scanner app or equivalent to monitor the DPF temperature or Cat Temp B1S2. It will get HOT, like over 600 Celcius at times. I’ve had readings of 670 C.

To maintain regeneration you need to keep between 30% and 70% load. You don’t need to floor it and stay in 4th gear for 45 minutes. This is a myth. In fact if you boot it the ECU will stop regeneration as it will assume you need the power.

My results were as follows. I would trigger a regeneration at 24g on the motorway at a steady speed. It would reach the hottest temperature here and achieve the most efficient cycle. Soot would start to plummet and as long as I kept a steady speed, didn’t stop or slow down for too long, it would get down to zero grams in about 20 minutes usually a little less. I recommend giving yourself at least 30 minutes on the motorway if you are not monitoring your soot levels.

At approximately 25g I would trigger a regeneration at A road speeds of 40 to 60mph. My car would happily regenerate for as long as I could maintain the speed. This included slowing down and brief stops. However it would not usually reach as high a temperature and soot levels would decrease at a slower but still admirable rate

At 27 grams to 29 grams (29g is the highest I’ve seen my dpf reach). My car would reach operating temperature and would initiate a regeneration as soon as possible at 30mph speed limits, in busy traffic, stop/starting and whatever else, it did not give one shit.

It does not want to risk getting a clogged filter. The soot level reduction was at its worst but would try it’s best to get you out of trouble. It would usually burn off 10 to 14g and then stop. This is the danger zone for people that only do short trips. This is when you’ll most likely interrupt the regeneration and if you do this a few times you’ll get ‘soot filter full’ message, if ignored then you’re into level 4 territory with ‘Engine Service Required’ message (to be clear this does NOT mean you simply need to service your engine. This is a problem that needs urgent attention.

In this case it means as expressed in Level 4 above, that the car can’t initiate a regeneration on it’s own anymore. It will need VIDA to initiate a Forced Regeneration! Not something I recommend doing on your driveway. (EDITORS NOTE..can take an hour of the car siting at over 3000rpm to do a forced regen…..its not cool…literally)

Other interesting things I discovered. Once a regeneration has started you can slow down and stop, park up and it will eventually interrupt the cycle and stop regenerating. BUT! As long as you don’t turn off your car I found that it will attempt to regenerate again even if your soot levels are now below the 24g threshold. If you do switch off you’ll have to wait until the 24g threshold has been achieved again before another regeneration cycle initiates.

Your car wants to regenerate. As long as it’s in good health and maintained correctly it will.

I have never had a warning message. I don’t do much motorway travel at all. This is why I wanted to make sure I wasn’t going to cause myself problems. You don’t need to constantly monitor your car. Eventually you’ll get a good feeling for how long it will take for your car to build up to 24g. Which is different for all of us, cold engines make more soot, revving higher makes more soot. Cold high revving makes ALL the soot.

I hope you found this useful.”

Cheers for taking the time Nathan

It seems to me that P3 platform cars have a much better relationships with the DPF than the P1 ad P2 platform cars. I was wondering if its because P3 will regen even when doing slow town driving.

Whilst the above is true for the D5 variant Nathan has, it varies by engine type a fair bit, all basically has the same overarching concepts.

(Original Post HERE)

Some example DPF trigger levels…

Here is Vida for a P3 D5244T16

Here is Vida for a P3 D4204T14

Here is Vida for a P2 D5244T18

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