[GUIDE] DPF Experiment and Results

[MrBenjaminHDM]

Originally Posted by SwissXC90

I did the calculations for my D5 powered XC90 and found that the DPF regen normally occurs once around every 1.5 tanks of fuel.

So as long as you do a motorway drive of at least 30min for every tank of gas, your car will always regenerate happily.

Not necessarily true I'm afraid, it's not that simple. The DPF will only regenerate once you're beyond a certain soot level. I'm averaging one Regen per one tank of fuel, the list of criteria in my original post is straight from VIDA and therefore your journeys and driving styles are a big factor. You seem to have found a sweet spot with your commutes.

For many of us the lure of £30 a year road tax, 64mpg and 0-60 in 6.7 seconds is too strong and we must learn to understand our DPFs more intimately.

[GusGecko]

Great stuff! Thank you for sharing.

[MrBenjaminHDM]

Originally Posted by GusGecko

Great stuff! Thank you for sharing.

Happy to help, it's a brilliant engine!

[antman99]

Just wanted to say thanks, great research and effort, not personally had a problem in my FWD D4 but good to know what to check.

[MrBenjaminHDM]

Originally Posted by antman99

Just wanted to say thanks, great research and effort, not personally had a problem in my FWD D4 but good to know what to check.

My pleasure, I've not heard of the rising oil level with the D4s I understand it was designed new from the ground up whereas the 5 cylinder D5s have been tinkered with over the years and weren't originally made to run a DPF.

Regardless, as you say it's great to know how to manipulate them for a long lasting and healthy engine.

[craigv60]

Do you have a feel for how quickly the soot levels fall once an active regeneration has started?

A LONG time ago, there was a post on Briskoda from someone who'd datalogged the progress of a regeneration from start to finish, while at a steady 65mph on a motorway. The car was a Superb with the 2.0 common-rail diesel.

From memory, the data showed that the soot levels fell from the active regen 'start' threshold, to less than 5% soot loading (which was the minimum level indicated by the ECU), in around 10 minutes - so the soot levels fall quickly.

However, the ECU continued post-injection for another few minutes AFTER the soot loading had fallen below 5%, presumably this is a margin to ensure that the maximum amount of soot is burnt off.

[MrBenjaminHDM]

Originally Posted by craigv60

Do you have a feel for how quickly the soot levels fall once an active regeneration has started?

A LONG time ago, there was a post on Briskoda from someone who'd datalogged the progress of a regeneration from start to finish, while at a steady 65mph on a motorway.

From memory, the data showed that the soot levels fell from the active regen 'start' threshold, to less than 5% soot loading (which was the minimum level indicated by the ECU), in around 10 minutes.

However, the ECU continued post-injection for another few minutes AFTER the soot loading had fallen below 5%, presumably this is a margin to ensure that the maximum amount of soot is burnt off.

As in the Original post my active regen test was conducted at 60mph and took 27 minutes from start to finish. The car had previously tried to regenerate on my drive to work which would suggest 27 grams of soot, it wouldn't have reduced on the way to work as it wouldn't have reached temp the first time.

I've not been able to watch the soot values live as I was alone in the car without the laptop. If I ever get a chance to I'll live log an active regeneration and update this post.

I'm not sure what Briskoda was logging but in my car the value is given in grams of soot and DPF pressure not % loading.

[craigv60]

Originally Posted by MrBenjaminHDM

I'm not sure what Briskoda was logging but in my car the value is given in grams of soot and DPF pressure not % loading.

I seem to remember that the VAG diagnostics expressed the soot content in the DPF as a percentage, rather than by weight, with an active regeneration being triggered at around 40% full .... but it was a while ago.

It's really useful information, thanks for posting.

[RoyMacDonald]

Originally Posted by MrBenjaminHDM

My pleasure, I've not heard of the rising oil level with the D4s I understand it was designed new from the ground up whereas the 5 cylinder D5s have been tinkered with over the years and weren't originally made to run a DPF.
.

Tinkered with is hardly the correct description. The original 163 bhp D5 is virtually a different engine to the 215 bhp D5. Hence the reason it was not fitted in the old XC90 because it would not fit in the chassis. The 185 bhp engines onward were all designed to run a DPF and have proved to be bombproof. They don't have issues unless there is an engine management fault.

Roy

[MrBenjaminHDM]

Originally Posted by RoyMacDonald

Tinkered with is hardly the correct description. The original 163 bhp D5 is virtually a different engine to the 215 bhp D5. Hence the reason it was not fitted in the old XC90 because it would not fit in the chassis. The 185 bhp engines onward were all designed to run a DPF and have proved to be bombproof. They don't have issues unless there is an engine management fault.

Roy

If we're going to play semantics then bombproof is hardly the correct description either, I don't think it would sustain a direct hit from a B61 nuclear bomb ;-).

The D5 engines have shared the same block, cylinder bore, stroke, turbos, common rail and compression ratios across different generations including 163-185. I'm not saying the DPF is an afterthought or even that it is done badly, what I am saying is that the D4 in it's current iteration was built from scratch to include a DPF. Over the years and even in this forum there has been DPF issues and oil level caused by DPF issues on the D5 highlighted and discussed.