The substrates are the backbone of the converter. This is where the proprietary mix of precious metal(s) and the washcoat formulated to store O2 allow the conversion process to take place. Converters are available in single- or multiple-substrate designs.
The mat cushions the converter substrate, holding the ceramic catalyst in proper alignment. Creates a seal between the substrate and body, making sure all exhaust goes through the catalyst. Allows for thermal expansion of the body.
Another vital part of an emissions control system. These sensors are placed before and after the catalytic converter on an OBDII vehicle. They are designed to monitor the O2
storage efficiency of the converter. This information also allows the PCM to adjust fuel controls.