33501116
Catalyst · Power Solutions International
Diesel oxidation catalyst, three-way catalyst and ammonia slip catalyst: operating principle, part number and replacement checks
The oxidation catalyst converts carbon monoxide and unburnt hydrocarbons into carbon dioxide and water on a platinum-palladium coating, and during active regeneration also generates the heat the downstream particulate filter needs to burn off soot. On gas-fuelled commercial and nonroad engines, a three-way catalyst instead converts carbon monoxide, hydrocarbons and nitrogen oxides simultaneously. An ammonia slip catalyst sits downstream of the SCR stage and oxidises excess ammonia.
The part number is tied to the precious-metal loading and the ratio of platinum to palladium, or on three-way catalysts rhodium, to the cell density and volume of the substrate, and to the lambda and temperature control tuned for the engine family. With every emission stage, coating formulation and housing geometry change, while for the ammonia slip catalyst the pairing with the upstream SCR catalyst also governs the design. The assignment of part numbers on this page comes from official certification documentation issued by the US Environmental Protection Agency.
Declining conversion efficiency first shows up through on-board diagnostics as an exceeded efficiency threshold. Thermal ageing from sustained high exhaust temperatures, poisoning of the coating by sulphur, phosphorus or zinc compounds, and mechanical damage to the substrate reduce catalytic activity permanently. A faulty ammonia slip catalyst shows up as increased ammonia slip, a faulty three-way catalyst as rough idling.
Replacement is governed by the part number, since outwardly identical housings can contain different coatings and substrate volumes. Checks should cover the sealing faces of the flange joints, the condition of the lambda and temperature sensor connectors, and the insulating jacket that limits heat loss. After replacement, many control units require an adaptation or learning drive for catalyst efficiency monitoring. Pricing and availability are not part of this page.
Fits these engines (2)
| Power Solutions International PSI LC8 CNG | Heavy-Duty-Straßenmotoren |
| Power Solutions International PSI LC8 LPG | Heavy-Duty-Straßenmotoren |
Excludes price and availability — those come from the supplier.