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Clairifacation of previous post

G

gordy from Iowa

Member

Subject was about a Cummings engine not using any DEF. not actually about tractors, but close. Pull two tractors and flat bed trailer with this engine.Anyway, had truck checked out. Every thing OK. Truck does not use a certain amount of DEF according to gallons of diesel used as some thought, Only uses DEF as needed to clean exhaust system. Can go a long time without any cleaning fluid being used.
 
DEF is used as a catalyst for the Catalytic Converter to remove NOx from the exhaust stream, unlike gasoline engines, the exhaust stream on a diesel isn't consistently hot enough to allow the catalytic converter to do it's job, that is why DEF is added. Also the amount of NOx in the exhaust is a function of the how hard the engine is working and this means the amount of DEF required varies. There is also a requirement to not allow excess DEF (ammonia) pass through catalytic converter.

That is to say that the amount of DEF varies depending on load and is not directly tied to the amount of diesel consumed or miles driven.

Rich
 
Use of DEF is definitely variable. I have a 2012 Volvo semi tractor that I use as my hauler. It has a Volvo D11 engine and is Tier 4 emissions. When fully loaded, it drinks DEF faster than a wino with a bottle in a bag. I also use it to pull my camper. With that light load, DEF usage is hardly noticeable, and fuel mileage is better than a pickup will do.
 
Never heard of a Cummings engine, must be European or something. I do have a 8.3 Cummins in a magnum though.
 
That is not correct, DEF does not clean out the exhaust. It is injected continuously into the exhaust so it can react in the secondary catalytic converter and convert the NOx into Nitrogen and water. You have two choices to reduce NOx, EGR, DEF or combination of both.

It has to use DEF or something is wrong, my truck does not seem to use a consistent amount, but does use it.
 
Use is not based on fuel consumption! That's fake news! ( 24 years and counting in research at cummins)
 


As most are saying, but contrary to what more smoke posted, Use of DEF is related to how the truck is used. A truck that is working under a load with some RPMs is not going to produce soot to accumulate in the filter. Low speed, low load, driving and idling will produce a lot of soot. Diesels SHOULD NOT BE IDLED!!!. Idling shortens the time between regens. The Mack that I drive occasionally gets idled too much. It goes through about 2 gallons / 100 gal of fuel, and regens every few weeks. My 2018 Fire Dept tanker to the best of my knowlege has yet to regen because it is rarely allowed to idle. Idling also causes wet stacking and dilution of oil with fuel which shortens engine life.
 
I remember this post and thought about replying then but didn't! Anywho I worked maintainence at an underground sand mine and had lots of diesel engines to deal with and found that you could have 10 of the same exact machine and they will not all use the same amount of def, had a couple that barely used any like you are talking about on yours then others loved the stuff!
 

DEF is used continuously at a rate that depends on the amount of NOx in the exhaust.

Regens do not use DEF. Regens use fuel. There are two different types. Those engines that are equipped with a particulate (soot) filter, inject extra fuel when the soot needs to be burned out of the filter.

Some engines do not have a particulate filter (primarily smaller off road), they only have 2 catalyst sections, the second one being where the DEF is used. In these, there can be a build up of crystallized urea. Once again, extra fuel is injected to heat the exhaust stream and clean the system.
 
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