From Grok - if you're interested?
In a turbocharged engine, a catalytic converter can "burn up" or fail due to a combination of factors that are either unique to or amplified by the turbo system. Here’s what could cause this:
First off, excessive heat is a major culprit. Turbocharged engines already run hotter than naturally aspirated ones because the turbo compresses air, increasing exhaust temperatures significantly—sometimes pushing past 1,000°F (540°C) under load. The catalytic converter, which needs to operate around 400-800°F (200-425°C) to function properly, can overheat if those exhaust temps spike too high. If the engine’s running lean—too much air, not enough fuel—the combustion gets even hotter, sending scorching exhaust straight into the converter. This can melt the internal ceramic honeycomb structure, effectively burning it up.
Then there’s unburned fuel, which is a big issue with turbos. If the engine misfires or the fuel mixture is too rich—too much fuel, not enough air—raw fuel can dump into the exhaust. In a turbo setup, this fuel can ignite either in the turbo itself or when it hits the hot catalytic converter downstream. This causes a secondary combustion inside the converter, spiking its temperature way beyond normal limits. Over time, or even in one bad event, this can degrade or melt the catalyst material, ruining it.
Oil contamination is another factor, especially with turbos. The turbo relies on oil for lubrication, and if its seals fail—say, from wear or overboosting—oil can leak into the exhaust side. That oil burns in the catalytic converter, coating the honeycomb with soot or carbon deposits. This clogs it up, increases backpressure, and traps heat, which can lead to burnout. A failing turbo bearing or a clogged oil return line can make this worse.
Backpressure itself is a sneaky problem in turbocharged systems. The turbo relies on exhaust flow to spin, and the catalytic converter sits right after it. If the converter’s already partially clogged—maybe from prior damage or contamination—it restricts exhaust flow. This builds pressure upstream, slowing the turbo spool and stressing the engine. The trapped heat can cook the converter further, accelerating its failure.
Finally, physical damage or poor tuning can push it over the edge. Turbo engines are sensitive to tuning—if the boost is cranked too high without proper fuel delivery, you get lean conditions or knock, both of which hammer the converter with heat and unburned fuel. And since the converter’s under the car, road debris or a hard hit could crack its shell, letting exhaust bypass the catalyst and causing uneven heating that leads to failure.
So, in short: extreme heat from lean running or turbo overboost, unburned fuel from misfires or rich mixtures, oil from turbo seal leaks, backpressure from a clog, or bad tuning can all torch a catalytic converter in a turbocharged engine. Regular maintenance—like checking turbo health, ensuring proper air-fuel ratios, and watching for misfires—can help avoid this mess.
