re: How to test a Cat
The simple answere is that there is no easy way and not really by looking at it.
A catalytic converter is a clay or ceramic substrate covered with a very thin layer of catalyst (the catalyst contains platinum or iridium, $$$). It goes bad in two ways:
1. The catalyst gets damaged or poisoned (by sulphur or lead in the fuel or all the other combustion by-products). This is why you have 2 O2 sensors, one measures O2 before and the other after the cat, if there is a delta, all is good. Once there is not, you will get a code and an engine light.
2. the small passages may get plugged up with all the exhaust going through them. The only way to test is to put a pressure sensor in the exhaust and see, if thepressure before the cat is acceptable/correct. If is start going up to 3 psi or more, it is plugged up.
The cat gets hot, because it burns up un-burnt exhaust. It is considered a fire hazard for track and other uses.
Anton
I have had it off a couple of times but you cannot see through element, or even the element face due to the curves. How can you verify when it is going bad?
Since I track the car, it should probably be removed.... I just don't really need a louder car or the raw gas smell for the street.