This is a two-scenario question really, we'll start with the easier one... Extending an exhaust? I want to extend the exhaust on a petrol generator, so the generator can be used inside a van or box trailer, but the exhaust fumes need to be routed outside. The generator will not be permanently fixed, so a flexible pipe would be the best option. It needs to be able to withstand heat, and transfer as little heat as possible (yes, I know, it's an exhaust so it will get hot, but the cooler it can be kept the better). What are the best options? Silencing an exhaust? I could do with one of the petrol generators running quieter, I was thinking of grafting a moped exhaust or similar on, would it make any difference?