Ok - so it won't raise the temps as much as going 90 will... that's great. But it will still raise the temps due to the increased flow of exhaust. The question is now "at what temperature will the DPF begin being cleaned?".
Obviously, the idea is to burn the particulates trapped in the
particulate filter, therefore, it would have to reach at least the flash point temp of each of those compounds that is being burned.
Doing some research - Wiki.com
Taken from -
Diesel particulate filter - Wikipedia, the free encyclopedia
Quote:
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In addition to collecting the particulate, a method must exist to clean the filter. Some filters are single use (disposable), while others are designed to burn off the accumulated particulate, either through the use of a catalyst (passive), or through an active technology, such as a fuel burner which heats the filter to soot combustion temperatures, through engine modifications (the engine is set to run a certain specific way when the filter load reaches a pre-determined level, either to heat the exhaust gases, or to produce high amounts of NO2, which will oxidize the particulates at relatively low temperatures), or through other methods. This is known as "filter regeneration". Sulfur in the fuel interferes with many "regeneration" strategies, so almost all jurisdictions that are interested in the reduction of particulate emissions, are also passing regulations governing fuel sulfur levels.
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Some thinking points:
How do you produce higher amounts of NO2?
Well, I'm not sure about in diesels, but if you really want NO2 production in Gasoline cars, you just lean the mixture a few points. Or advance your timing a few degrees.
Obviously, diesels *generally* don't have "timing", such as gas engines do, however, it is quite possible to lean the mixture of a diesel engine.
How to lean the mixture of ANY engine.
Rev it high. Period. The fuel system of an OEM equipped engine is not designed to provide a stoich ratio (not relevant for diesels) at high RPMS, and cannot compensate for the quality of air at those levels. Friction at this RPM raises engine temps, which in turn insulates combustion chambers to create higher ignition temps and pre-ignition in diesels (pre-pre-ignition, really, since they *generally* run on pre-ignition anyway.)
The resultant higher combustion chamber temp, including the leaner A/F mixture, creates more heat than normal, which could in turn to be used to "regenerate" the particulate filter.
Conn- PLEASE don't misinterpret this as an argument to what you're saying - it's not.
I'm simply saying that at 90 mph or at 20 MPH, the exhaust temp will still increase, just maybe not as much, or as quickly, and that the filter itself relies on heat to regenerate, which is not necessarily caused by a richer mixture, as many would report.