Metal Honeycomb Substrates

Troubleshooting Common Issues in Metal Honeycomb Substrates

On diesel engines, metal honeycomb substrates can give you headaches if you don’t pay attention. I’ve seen plenty of converters fail or underperform, and most of the time, the problem isn’t mysterious—it’s installation, heat, vibration, or just neglect.

Cracks in the substrate show up more often than people expect. Engines that heat up quickly and cool down just as fast put a lot of stress on the metal. If the converter isn’t mounted perfectly or the brackets don’t hold it tight, the honeycomb can flex, and micro-cracks appear. At first, you might not notice, but efficiency drops, backpressure increases, and emissions readings go up.

Clogging is another common issue. Diesel engines leave behind soot, ash, and unburned fuel residues. Over time, these build up inside the honeycomb channels and restrict flow. High backpressure is the first sign—you’ll feel the engine hesitate or lose power. Engines that run at high load or go through frequent start-stop cycles clog faster, so inspection and cleaning schedules matter.

Coating wear is tricky because it’s not always visible. Oxidation coatings deal with CO and hydrocarbons; SCR coatings take care of NOx. If the coating flakes, wears unevenly, or gets contaminated, the substrate will fail to convert gases efficiently, even if it looks intact.

Installation mistakes make everything worse. Uneven exhaust flow, hotspots, vibration without damping—they all shorten substrate life. I’ve seen converters crack within weeks because someone didn’t align it properly or ignored heat shield placement. Even small errors multiply over time.

Maintenance is straightforward but essential. Check for cracks, flow restrictions, and coating wear. When replacing a substrate, match the original material, honeycomb design, and coatings. Even minor differences can cause stress points, flow problems, or faster degradation.

At the end of the day, a metal honeycomb substrate will perform reliably if installed correctly, maintained regularly, and treated with care. Skipping these steps will always show up in backpressure, engine performance, and emissions.