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.
| Constituent | Volume percent | Parts per million |
|---|---|---|
| Carbon Monoxide | 1 | |
| Oxygen | 1.3 | |
| Carbon Dioxide | 3.8 | |
| Water Vapor | 10 | |
| Sulfer dioxide | 20 | |
| Oxides of nitrogen | 280 | |
| Hydrogen | 3500 | |
| Hydrocarbon* | 4000 | |
| 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.