Exactly what speed/revs/time period is needed for a DPF regen?
#1
04-01-2014, 09:05 AM
Exactly what speed/revs/time period is needed for a DPF regen?
I've seen a lot of advice saying to run the car for x minutes at y revs (or z mph), but what is the definitive answer? The owners handbook is quite vague and just suggests driving above 50 mph for 15 minutes (I can't quite remember and don't have the manual in front of me).
Most of my driving is my 7 daily mile commute to work, across town and on some country roads (I get up to 50mph for about 3 minutes), the rest is short trips around town, BUT I've always made a point of taking it on a longer trip once a week, at least 15 minutes on the motorway above 70mph. I assumed this should be enough to clear the DPF, but maybe it isn't. Should go for longer or more frequent? Should I be doing it in 4th gear instead of 6th?
Most of my driving is my 7 daily mile commute to work, across town and on some country roads (I get up to 50mph for about 3 minutes), the rest is short trips around town, BUT I've always made a point of taking it on a longer trip once a week, at least 15 minutes on the motorway above 70mph. I assumed this should be enough to clear the DPF, but maybe it isn't. Should go for longer or more frequent? Should I be doing it in 4th gear instead of 6th?
#2
04-07-2014, 03:40 PM
Regen requirements
Iainso - a few thoughts.
I suspect there is no absolute answer as to some extent it will depend on the condition of the fuel injectors and the overall combustion system.
When I bought my car 5yrs ago all this diesel technology was new to me so I asked the mechanic at the Mazda garage. His answer "Drive for 20 mins at over 2000rpm". This is still somewhat vague as it makes no reference to how or for how long the car is driven each week.
One guide could be to check the oil level - if it looks like it will be over 3/4 full between 12500 mile services then it is being regenerated by the engine management system too many times. This would indicate the need to regen by driving at high speed etc more often.
My car never sees a motorway - we do not even have any dual carriageways in the county but I have not had any regen issues so far. ( Apart from a false DPF light when the mechanic did not reset the computer after an oil change). Admittedly I am generally able to do longer runs at 50- 60 mph (1800-2200rpm) than you describe.
One other thought. My car has just had a major service (73000) miles where the cam belt was changed. As part of that they also removed and cleaned each fuel injector. I do not know what milage you are at but if this was not done especially on a car doing a lot of stop/start low speed driving it could cause excessive regen. as the DPF becomes blocked.
As part of the service they also changed the cambelt tensioner. This cost about another £160. I do not know if a worn one would affect the combustion or whether the engine management system would compensate for it.
From your description I would take every opportuntity to drive it hard.
Hope this is of some help.
2008 Mazda 5 2.0D Sport.
I suspect there is no absolute answer as to some extent it will depend on the condition of the fuel injectors and the overall combustion system.
When I bought my car 5yrs ago all this diesel technology was new to me so I asked the mechanic at the Mazda garage. His answer "Drive for 20 mins at over 2000rpm". This is still somewhat vague as it makes no reference to how or for how long the car is driven each week.
One guide could be to check the oil level - if it looks like it will be over 3/4 full between 12500 mile services then it is being regenerated by the engine management system too many times. This would indicate the need to regen by driving at high speed etc more often.
My car never sees a motorway - we do not even have any dual carriageways in the county but I have not had any regen issues so far. ( Apart from a false DPF light when the mechanic did not reset the computer after an oil change). Admittedly I am generally able to do longer runs at 50- 60 mph (1800-2200rpm) than you describe.
One other thought. My car has just had a major service (73000) miles where the cam belt was changed. As part of that they also removed and cleaned each fuel injector. I do not know what milage you are at but if this was not done especially on a car doing a lot of stop/start low speed driving it could cause excessive regen. as the DPF becomes blocked.
As part of the service they also changed the cambelt tensioner. This cost about another £160. I do not know if a worn one would affect the combustion or whether the engine management system would compensate for it.
From your description I would take every opportuntity to drive it hard.
Hope this is of some help.
2008 Mazda 5 2.0D Sport.
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