AFTERTREATMENT TECHNOLOGIES
To meet Tier 4 Interim emissions standards and beyond, Cat aftertreatment components have been designed to match application needs.
For small to medium applications: 
Service-free compact systems Passive regeneration No supplemental fuel needed
For medium to large applications: Durable packaged systems designed to withstand even the most demanding applications Fuel-efficient, reliable regeneration Operates automatically
Cat Aftertreatment components include: Diesel Oxidation Catalyst (DOC).
The DOC uses a chemical process to transform pollutants in the exhaust stream into less harmful components.
Diesel Particulate Filter (DPF)
A DPF traps additional particulate matter that's carried in the exhaust stream, preventing it from being released into the atmosphere.
Passive Regeneration System (C4.4 ACERT, C6.6 ACERT)
All Cat Tier 4 Interim engines use a passive regeneration system that continually regenerates at a slow rate, during normal machine operation, using the heat from the engine's exhaust gas.
Cat Regeneration System (C7.1 ACERT-C18 ACERT)
The Cat Regeneration System (CRS), is an active regeneration system used in engines rated130-560 bkW (175-750 bhp) when supplemental regeneration is needed. CRS elevates exhaust gas temperatures to promote oxidation and burn off soot in the DPF.
