diesel particulate filter requirements

[matmce]

Hi All
I have a question relating to the DPF in an D40 auto 07 STX (or any DPF for that matter). I have done a search and read quite a few threads but could not find an answer.
How often should the car be driven at the appropiate speed for a full generation cycle without waiting for the light to come up on the dash (which has not happened to me yet)
Now before everyone tells me how the DPF works, i have owned the car for a couple of years now and i don't think i have had any problems with the DPF. I have aslo been reading lots about them and i understand how they work (active and passive regeneration)(It still confuses me which one is which). But i have yet to read anything that tells me the following things.

How many times, lets say per tank, should i drive at highway speeds. Once, twice, more or less??
I"m wanting to know as a general rule (and to save on fuel) as i only travel a short distance to work and back for most of the tank of fuel. I do try to go for a bigger drive when i can, but its not always possible to get to the required speeds for the required time.
Anyway i hope everyone understands the question (yes there is one in there somewhere)


Cheers

 

[KraftyPg]

There is no set number no set distance and no set calculation to run a car at to make the regen not happen, regens will happen when and where required.

Shorter trips can make the regen cycles more frequent but there is nothing to say that it's 1 trip or 10. Longer trips should see the DPF burn off as required and that requirement will probably be less often but there is still no figure that says when the regen will take place. On longer trips it appears the chance of the driver having to interact are less but again not calculable.

Regens are automatic and happen mostly without the driver knowing unless the driver knows what they are looking for, some suggest regens happen atleast once every 1000ks, some suggest more but the one thing that is definite is they happen automatically when the car needs it. The only time you will see the light is if your current driving is not letting the regen happen.

The fact you have not seen the light simply means your driving up until now has been satisfactory to allow the regen to complete. Keep driving until you see the light, then remember the 80kph/2000rpm theory and you'll be fine.

 

[matmce]

Thanks for the reply.
That's basically what I thought.
Now, here's one for all those of us that are for a better word 'anal'.
How much fuel do you think the "active" regen" cycle adds to fuel consumption?

 

[KraftyPg]

Next to SFA.....unless your a DPF fearing SOB and then it's 4 million litres a regen.

There is no exact figure because there is no set time for a regen to occur but it is also very dependent on conditions.

The first time I noticed mine come on I dropped a cog and drove it for about 5ks in a 60 zone because I couldn't get to a 100 zone any sooner. Another time it came on I had to drive at highway speeds for nearly 30ks before the light went off. Every time is and will always be different.

 

[Old.Tony]

I did read somewhere that regens can occur between 100 and 300km apart (I think BossHog discovered this when his regens were resulting in clouds of white smoke). That shouldn't be considered definitive - his Navara was by no means "standard". Regens can take up to 10 minutes if memory serves, but you'd have to think that once the car decides a regen is needed because of the pressure differential between the two sensors, it will monitor the difference and once it's within a certain range it ought to stop the regen.

I don't know that BossHog's experience was "typical". To emit clouds of white smoke you'd need a fair bit of fuel. I don't think a regen uses that much fuel - some of us (like Krafty) can get similar or better economy than manuals, so clearly the DPF isn't hugely thirsty.

As Krafty said, if your light has never come on (and DOES come on during initial startup) then whatever driving style you have is obviously appropriate.

 

[KraftyPg]

If you want to test your DPF it can be done....sort of. It wasn't exactly deliberate but my driving pretty much caused the light on the dash a few months ago.

I'd done a large number of short trips and I was doing one particular short trip back from my parents and was deliberately driving and keeping the revs as low as possible just playing with fuel figures in my head. Was all 40-60 zones and there was almost no traffic (joys of country towns) to hamper my little test but it was also bloody cold.

Together with the outside temp, the engine not running hot and the slow driving I wasn't surprised when the DPF light came on simply because it stands to reason I wasn't giving the engine what it needed to keep the DPF clean. But again the regen happened exactly as I expected it too.

It's obviously not a definitive test and may not be recommended by Nissan but I know my DPF, it's regen and it's request for me to help said regen all work. But above all I also know that with standard driving even if that standard driving is mostly in lower speed zones I'm not having to fear the fact that there is a DPF under my car just ticking away like some secret time bomb.

 

[matmce]

Thanks for the replies, it put my mind partially at rest knowing my driving style isn't as detrimental as i was thinking. It also helps me understand my fuel usage as i generally get much better figures on a return long highway trip.
Thanks again and thanks to everyones thoughts, opinions and knowlege on this forum. It has served me well in the past.
Cheers