I did, and it said...
Quote:
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If the overheating condition persists for a long period of time, or if the temperature soars high enough, the honeycomb itself may breakdown and melt forming a partial or complete obstruction and causing a sharp rise in backpressure.
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Since we're talking about the mixture being slightly richer until the car warms up, maybe ten minutes or so, we aren't talking about an overheating condition that persists for a long period of time. We also aren't talking about really high temperatures unless we have something that's running extremely rich at very high torque/power outputs. For instance,
this SAE paper shows via Figure 8 that in order for a cat to reach the damage threshold in terms of temperature it needs a 20% misfire rate, which corresponds to a A:F ratio of under 12:1, at 3000rpm and a fairly heavy load of ~4kg*m=~28ftlb. To put that into perspective a 2L engine from Hyundai when the paper was published makes ~120ftlb at 6000rpm, and ~60ftlbs@3000rpm, so at half load for a 2L engine, 3000 rpm, and a constant less than 12:1 A:F ratio, we can get into an area where the catalyst is at risk. That said, most people don't start up their car and use on average ~30+hp while keeping the engine cold enough to stay w/ the richer A:F mixture constantly. In other words the only way the cat would be at risk is w/ the engine running constantly richer, not just during the warm up.
So in order to see a risk for the cat we would need to run constantly at 12:1 and half of the engine's likely maximum speed and maximum torque. Since an engine run like this is going to warm up very quickly, I doubt we can stay at 12:1 and ~30hp long enough to do any damage to the cat. If we go richer than 12:1 we'll have something that will probably bog down and run poorly, which wouldn't be something a manufacturer would do. Furthermore, higher power outputs require higher speeds and the airflow under the car would help keep the cat cool. I'm betting that short of a constantly rich mixture manufacturers design prevents damage to the cat from being a problem even during WOT cold starts.