Ford 2012 Super Duty Pickups F-250 User Manual page 17

F-250/F-350/F-450
Super Duty Pickups
The Selective Catalytic Reduction (SCR) has strong advantages over the competitive lean NOx trap system,
similar to what a customer would find in a Ram Pickup truck.
Lean NOx Trap
• Diesel engines normally operate with an excess
ratio of air-to-fuel (also known as "lean" operation)
• A Lean NOx Trap (also known as a NOx Adsorber
Catalyst) chemically traps the NOx in the
exhaust on the surface of the catalyst during
lean engine operation
• As the surface of the trap becomes full, the
system triggers the engine to run rich (increases
the fuel-to-air ratio) to clean the trap
What's an Absorber?
We're all familiar with something that absorbs: a sponge. A sponge soaks up (absorbs) a liquid from the
outside and stores the liquid internally until full. Once the sponge is full, it stops absorbing and can only take on
additional liquid if drained (squeezed).
What's an Adsorber?
An adsorber, on the other hand, attracts and holds particles on an outer surface — similar to a pleated filter on a
vacuum cleaner, a furnace filter or charcoal granules in a vapor canister.
June 2011
Performance/Handling
Diesel Engine Emissions cont'd
MAKE THE POINT: SCR Competitive Advantages
SCR Advantages
• Designed for greater fuel efficiency compared to
• Lean NOx Trap systems constantly cycle between a
• Lean NOx Traps also trap the sulfur in diesel fuel and
• It's expected that in the future all OEMs will rely on
ENGINEERING INSIGHT
Absorber vs. Adsorber
esourcebook.dealerconnection.com
RE&T: 2012 Source Book
2012
Lean NOx Trap
lean and a rich fuel mix, which consumes more fuel
than an SCR system
can become clogged, requiring a higher temperature
regeneration to remove the sulfur from the trap
this technology
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