Basics

Often abbreviated as DEF
A Consumable Fluid Used for Selective Catalytic Reduction (SCR) systems (essentially wet scrubbers/gas-liquid contactors, but scaled down) mainly on portable diesel engines to reduce NOx emmissions
Is essentially an aqueous urea solution
According to wikipedia:
- an aqueous urea solution made with 32.5% urea and 67.5% deionized water
There are some issues with amonia venting off over time and it thus getting "weaker"
The injection rate of DEF into the exhaust depends on the specific after-treatment system, but is typically 2–6% of diesel consumption volume
Commercial Truck Stops Have it "On tap" ie from a pump in most cases
Most consumers get it in small disposable tanks
- Can often be "expired" with this sales model
Supposedly small issue with excess amonia out of the exhaust if dosage ratio is off (simple control issue)
May be irrelevant if (near)Stoiceometric Diesel Combustion Can Be Reached (and thus standard Catalytic Converters can be used

To-Do

Any way to sense offgassing? Also what sensors are needed, outside of standard oxy-fuel ratio sensors (ie ammonia gas sensor, liquid sensor...)
DIY Via pelletized/powderized urea? (aggricultural supply, may store better)
See how far off Stoic Diesel is, if it even is possible