Bully Dog and SCT in hot water with the EPA

[SuperBuickGuy]

Again, I doubt it is the DEF that is causing the fuel economy drop. It's the particulate filter and specifically the particulate filter regeneration cycle that is the true cause. The exhaust particulate filter is regenerated fairly often** by injecting extra fuel into the cylinder while the exhaust valve is still open. Both DEF and particulate filters were added to diesel passenger vehicles at about the same time so most people conflate the issues with them.

** So the real question is how often do the OEM's schedule the particulate filter be regenerated? Initial press releases mentioned regeneration intervals of "approximately 100 miles" and thus "no significant impact on fuel economy". However, I suspect that 100 mile number was under ideal conditions that the real world schedule is more like once every 10 miles which obviously does affect fuel economy.

this isn't guess, this is observed and verified.

the DEF system regenerates about once every tank full. To do so, it heats up the exhaust by adding extra fuel with the extra fuel it adds the cow pee which creates hotter exhaust which cleans the cat.

In other news, no, DEF is not readily flammable ....

[Aircooled]

the DEF system regenerates about once every tank full. To do so, it heats up the exhaust by adding extra fuel with the extra fuel it adds the cow pee which creates hotter exhaust which cleans the cat..

You are still conflating two separate emissions control systems DEF and DPF.
DEF (Diesel Exhaust Fluid) injects urea into the SCR (cat) to reduce NOX emmisions. No regeneration nor extra fuel requried.
DPF (Diesel Particulate Filter) is a filter in the exhaust that captures soot to meet the diesel particulate emissions regulations. This is the system that is regenerated by dumping extra fuel into the exhaust to burn off the captured carbon.

[DanStokes]

Aircooled, you're a tad off. There are a couple of possible scenarios to treat NoX in the exhaust stream (some systems use a separate brick in the aftertreatment can) but in any case NoX is ADsobed onto the surface of whatever medium is used to catch it - it is not "converted" like HC, CO, and NoX are on a gas-fueled engine's cat. The NoX adsorber and the DPF both can be regenerated by adding either more fuel or DEF to heat the surface which subsequently converts the NoX to N2 and water vapor.

I've been retired for 15 years but I'm pretty sure I've retained this info properly though old age is a b1tc#!

Dan