40 CFR 90.329 - Catalyst thermal stress test.
(a)Oven characteristics. The oven used for thermally stressing the test catalyst must be capable of maintaining a temperature of 500 ±5 °C and 1000 ±10 °C.
(b)Evaluation gas composition.
(1) A synthetic exhaust gas mixture is used for evaluating the effect of thermal stress on catalyst conversion efficiency.
(2) The synthetic exhaust gas mixture must have the following composition:
|Constituent||Volume percent||Parts per million|
|Oxides of nitrogen||280|
|Nitrogen = Balance|
* Propylene/propane ratio = 2/1.
(c)Phase 2 engines. The catalyst thermal stress test is not required for engine families certified to the Phase 2 standards.