Light Off Catalyst

As the catalyst heats up, converter efficiency rises rapidly. The point at which conversion efficiency exceeds 50 percent is called catalyst light off. For most catalysts this point occurs at 475-575°F (246-301°C). A fast light catalyst is a 3-Way Catalyst (TWC), that is located as close to exhaust manifold as possible. Because light off catalyst is located close to exhaust manifold it will light off faster and reduce emissions quicker than the catalyst located under vehicle. Once catalyst lights off, the catalyst will quickly reach maximum conversion efficiency.