- The catalytic converter was initially introduced in the early 70s because of EPA-ordered cuts in emissions.
- Lab work finally proved that a catalytic converter would work, but mass-producing them became a new and even more difficult hurdle.
- With the OBD2 regulations that came about in the mid-90s, a second O2 sensor was added behind the front catalyst brick to monitor the catalyst’s ability to store oxygen.
The catalytic converter was initially introduced in the early ‘70s because of EPA-ordered cuts in emissions, and in response to those orders, auto industry execs said the EPA’s targets could never be met. But thanks to old-fashioned American ingenuity, they were. What the EPA conceives, American engineers always achieve. Fuel-cell engineer Jonathan Frost once said:
“When the U.S. introduced clean air legislation in the 1970s, many engineers said that cleaning up emissions from cars was impossible, but the legislation was passed anyway and new technology was invented in the form of the catalytic converter.”Jonathan Frost
In 1972, then Ford President Lee Iacocca said that “if the EPA does not suspend the catalytic converter rule, it will cause Ford to shut down.” He was obviously wrong, but at the time, the prevailing wisdom was that the catalytic converter was a near-impossible concept, overly expensive and inefficient, pegged as an idea that would never, ever work.
The Origins of the Catalytic Converter
The 1970 requirement that auto manufacturers would be required to reduce harmful emissions 90 percent by the 1975 model year drove Engelhard Industries and Corning Glass to propose the device that would later become the catalytic converter. A “catalyst” foists chemical changes on other elements while resisting any change in itself.
The catalytic converter adds the necessary oxygen molecules to CO and HC (the exhaust from rich mixtures), to change those harmful elements into CO2, which is the same thing we breathe out. The exhaust gasses flow from the combustion chambers through the catalytic converter’s core, which is a block of ceramic material honeycombed with tiny lengthwise channels, designed to force every cubic millimeter of the gasses into contact with the catalyst material, and that’s where the necessary changes take place.
Mass Production of Catalytic Converters
Lab work finally proved that a catalytic converter would work, but mass-producing them became a new and even more difficult hurdle. Engineers would have to take an abrasive clay mixture and force it through a shaped die at high speed to create the complexities of structure we see in Cat-Cons today. This process is called “extrusion” and at the time it was very commonly used for creating things like metal pipes and hollow noodles, but nothing anywhere near this complex had ever been attempted. It was a daunting task.
But that wasn’t all. Once that soft block of honeycombed clay emerged from the die, it first had to be cut to the proper length and then heated simultaneously inside and out until it was totally firm. And all this had to be done without distorting those tiny channels or causing the clay to crack, and then they had to find a way to coat all the channels with a layer of very fine platinum particles so that the platinum wouldn’t simply fall off after repeated (and vast) temperature swings.
Under normal conditions, a catalytic converter races from ambient temperature to 800° F in 30 seconds, and the temperature of the gases can climb as high as 2,000 degrees. Catalysts will normally float between 1000 and 1700°F while driving. In early development, on nearly every prototype, thermal expansion ruined the guts of the converter after just a few drive cycles.
But then it was discovered that samples of clay from one mine in Georgia showed much better heat resistance. This clay turned out to consist of microscopic needle-like units aligned in such a way as to withstand the thermal expansion, and that was the key to making a cat that would last.
With the OBD2 regulations that came about in the mid-90s, a second O2 sensor was added behind the front catalyst brick to monitor the catalyst’s ability to store oxygen. The sensor behind the catalyst is typically lazier than the sensor between the catalyst and the engine when the catalyst is working properly.
Watch this video to understand how catalytic converters work:
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