[spirilis]

I've had a mod floating around in my head for a while, and a rather minor experiment (on my maxi-scooter--a 2006 Yamaha Majesty) to report.

The question is whether it is worth adding some kind of header wrap or metal heat shield (even an aluminum foil wrap might work, as a low-emissivity arrester to slow/reduce radiant heat loss) to the exhaust system AFTER the catalytic converter.

I say AFTER the catalyst because while it might help wrapping the manifold and pipes before the catalyst, it's probably not a good idea to do anything that could run the catalyst hotter than it was designed for (risk of overheating).

On thinking about this, what came to mind is that if the pipe is hotter, the exhaust gasses may stay hotter further downstream from the engine and with hotter gasses come lower density, thus while the engine is still pushing the same amount of exhaust in both the control instance and the pipe-wrapped instance, the gas should move faster through the pipe-wrapped example thus reducing backpressure from cooling/condensing exhaust (I think?)

Any thoughts? Crazy idea or worth experimenting? (Or has it been done before...?)

Actually before closing I should mention the anecdote I do have--my Majesty scooter, I wrapped some foil around the exhaust pipe from the head to the furthest section I could get without fiddling with the pipe's mounting hardware, and while it's all VERY subjective I could swear I noticed more "punch" from the engine after it was warmed up. That could very well *all* be in my head though, and I wasn't keeping good fuel economy records with that thing before & after the experiment.