What do you all think of injecting DEF on the 6.4 at regen to increase clean and less regens! Just a thought! I was thinking of getting parts form 6.7 to use. Maybe a button pushed on regen Input Please

 

Def is used because of nox, DPF is used for soot. Would not help with the burning off of the soot.

 

I think there might be more to it than that. Go back to when we first started discussing urea around here. From what I remember, urea is what several manufacturer's wanted to use for the 07 emissions requirements, but the EPA nixed the idea of a user added emission system. That was the big hit on MPG's for the 6.4 supposedly.

It's not strictly the NOx vs. soot argument, but the emissions tuning package that improves when you're allowed to factor urea into the equation. If more states keep sniffing diesels during inspections, maybe someone will come up with a tune to do this. Otherwise I'm guessing the tuners will keep with the delete tunes and just not worry about it.

 

No, that's not a good idea unless you just want to void your warranty. If it's DEF you want, then get a truck with a 6.7.

 

As has been stated about urea, it is for NOx.

That having been said, there are two ways to decrease emissions on these engines. One is to run the engine lean to produce less soot. The drawback is it produces more NOx. Then there is the opposite - run the engine rich to decrease NOx, but it produces more soot.

The 6.4 runs on method 2 - runs ritch to bring down NOx and catches the soot in the DPF. Adding urea, without changing anything else, would be attacking the NOx and would do nothing for the soot and DPF/DOC.

The 6.7 uses method 1. It runs leaner, producing less soot, but also produces more NOx. The urea/DEF attacks the NOx while the DOC/DPF still handle the soot. By emitting less soot the DPF works that much less on regens, and by running the engine leaner there is less fuel consumed from the start. So fuel efficiency goes up on two fronts - lean and less regens. The opposite is true of the 6.4 - rich and more regens.

I would be curious to know what the total fluid efficiency is of the 6.7 with the use of urea. You may get better fuel mileage, but you also have to worry about DEF now too. Adding another expendable to the vehicle that increases fuel mileage doesn't in itself make it "more efficient". Both fluids have to be factored together.

 

Great post! You explain the emissions control strategy well.

A 2.5 gallon jug of DEF goes for around $14.00 at O'Reilly auto parts. That much DEF would last ~3,000 miles.

 

Yes, you can feel good that us 6.7 owners have yet another thing to keep up with to run a diesel engine. Fortunately, approx. 1,000 MPG for DEF is not exactly something significant enough to blow up the cost per mile spreadsheet.

 

I glad I asked I was told DEF was injected to help clean DPF soot!

 

Just to clarify a little bit (I know all of this because I co-own an emissions company), the DEF doesn't reduce NOx by itself. It merely needs to be present for the proper reaction to take place within the catalyst.

The DEF is injected into the exhaust stream far enough before the SCR (Selective Catalytic Reduction) catalyst so that the fluid is evaporated into the exaust stream, which then leaves only ammonia. The ammonia reacts in the SCR to reduce NOx. Typically a DPF (Diesel Particulate Filter) or a DOC (Diesel Oxidation Catalyst) is placed upstream of the injection point and the SCR to protect the SCR from particulate. Some applications (large power plants, etc) inject aqueous ammonia instead of DEF - DEF caught on because it is much safer and doesn't need to be regulated like ammonia.

Dosing DEF upstream of the DPF or DOC would probably ruin it - these filters are very sensitive to contaminants other than exhaust gasses. For example if you blow a turbo and shoot a bunch of oil down the exhaust pipe, your whole emissions system is probably shot.