You’ve finished installing your freshly wrapped headers and exhaust, but a few minutes after firing up the engine, you notice wisps of smoke coming from the engine bay and exhaust. You open the hood and nothing is on fire, but your freshly installed exhaust heat wrap is smoking like it’s going to catch on fire. Not to worry—this is actually normal for newly installed exhaust wraps that haven’t yet been exposed to heat.
Exhaust/header wraps are made with binders, which are specially formulated starches that give the wrap’s fibers some structure and lubrication during the weaving process. Once the manufacturing process is done, the job of the binders is complete, and when exposed to exhaust heat they tend to burn off, creating the aforementioned smoke after using exhaust wrap.
Another question often asked is why cheap wraps become brittle after a period of time/heat cycles and can disintegrate. This is the result of the wrap being exposed to temperatures beyond its operational rating. When a wrap sees too much heat, the chemical state of the fibers changes from being fibrous to a weak crystalline structure—essentially a very thin and fragile glass that shatters easily.
Above: Heatshield Products Lava Exhaust Wrap is rated for a continuous 1200-degrees Fahrenheit and intermitten max temp of 2000-degrees. Because of this and its makeup of volcanic rock fibers, Lava Exhaust Wrap won't become brittle and fall apart even after numerous heat cycles where it sees high temperatures.
Additionally, the maximum sustainable temperature (continuous) is often misrepresented on cheaper wraps; what’s listed is typically the maximum temperature they can withstand for less than a minute. That’s why it’s important to shop according by the continuous temperature rating of wraps, and make sure that rating is more than what your exhaust will normally see. And if you’re not sure, always err on the side of caution and use an exhaust tape or wrap with the highest rating possible.