Catalytic converter cold-start emissions problem

Stage demonstration with two catalytic converters — ceramic (Corning extrusion) and a metallic Fe-Cr-Ni-Al-Y alloy substrate. The metal version was studied as a lightweight, fast-heating alternative because cold-start emissions occur before the heavy ceramic substrate reaches operating temperature. Inspection-station advice to run the engine 20 minutes connects to this.

You need to understand there are different properties. Structural materials have tensor mechanical properties, all kinds of different properties. Functional materials have chemical properties, magnetic properties, all kinds of things. [Tom holds up a ceramic catalytic converter substrate.] Here's an example of a catalytic converter. A ceramic substrate that takes the platinum or palladium catalyst. [Tom holds up a second, metallic catalytic converter.] Here's another one, only this is made out of metal. This is made out of a high-temperature metal, because you've got gases going through here at above 2000 degrees. Most metals are going to oxidize and melt, so they have to use a ceramic which has high temperature capability. This is the type of catalytic converter you have in your car. It's made by Corning by an extrusion process, very proprietary, to get thin walls.

Tom shows a low-thermal-mass platinized stainless-steel catalytic converter designed to heat up quickly to handle cold-start emissions, contrasted with heavier ceramic monoliths. Student notes BMW failure mode of cooling between cycles.

[Tom shows a stainless steel catalytic converter.] This is not your typical ceramic catalytic converter. I could have brought a ceramic one, but they're heavier. This one's made out of a very fancy stainless steel and they would platinize the exhaust. It's very lightweight. They wanted to design that because most of your emissions problems are when you first start up the vehicle. The catalyst isn't working when it's cold. When you start up the vehicle, all your emissions go right out the back until you heat up the catalyst and it starts working. If you've got a big thermal mass, it takes longer to heat up, and so it might be two or three minutes where you're spewing out all kinds of pollutants. You'll pass the test at the shop if you've run your car for 10 or 15 minutes, but if you went in fresh and tried to pass the test, your catalytic converter isn't working — you'll flunk the state inspection.