The care and feeding of your DPF

Submitted: Wednesday, Aug 23, 2017 at 16:28
ThreadID: 135450 Views:8241 Replies:9 FollowUps:58
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Since I am in the process of buying a new diesel powered tow vehicle which will mainly see duty dragging our van around, and of course the odd bit of sight seeing, I thought I might do a bit of research on the above subject. This considering that the fitment of these devices seems to be the latest attempt by manufacturers to make diesel exhausts as clean as mountain air.

From what I have been able to understand, a DPF is little more than, as the term implies, a filter to catch soot particles which is a "natural" and apparently extremely carcinogenic, byproduct of burning diesel fuel. Along of course with a bunch of other nasties.

By all indications, I shouldn't have gotten anywhere near to my present 3 score years and 10 and not have long ago departed this mortal coil, so to speak. Having spent most of my working life driving, tuning, trouble shooting, re-building and dyno testing these dispicable machines.

Anyway, it appears that the "stuff" the average DPF captures is basically soot, carbon or somewhat unburnt particles present in exhausts. Now my understanding is that black smoke was an indication of overfueling or lack of sufficient oxygen or too low a temperature to achieve efficient combustion Now like any filter, a DPF can only trap and contain a certain amount of particles.

When the quantity becomes too great to permit the flow of exhaust gasses below a certain value, a "regeneration" process takes place. This basically raises the temperature in the exhaust system and therefor the DPF, basically "burning" off the excess load that is blocking up the filter medium. Apart from a rather acrid smell there is also a quantity of ash which is theoretically expelled from the exhaust pipe.

All good for some variable period, depending on vehicle usage.
Unless I misunderstood the reason, the fitment of exhaust gas recirculation (EGR) features was to lower the combustion temperatures and therefor the reduction of nitrous oxides (NoX???) or some such. The lowering below optimum combustion temperature of pretty much any fuel, results in incomplete combustion.

Ever watched a dog chasing it's tail. Unless the dog is very flexible or it's tail abnormally long it rarely catches it. (;-((

Cheers
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