[morgan46]

I cant remember exactly, but it has something to do with keeping the exhaust gases hotter in the pipes.
I'm sure someone will know about it better!

And keeping the heat away from the airbox!

 

[morgan46]

So there is a function behind it and not just aesthetics

:NefRider:

Yep Header wrap retains the exhaust gas heat IN the pipe, reducing the passing by air from dropping the temp until it exits the pipe. The reason for this is increased exhaust gas velocity.....heat moves towards cold due to it's higher pressure....example, in your bathroom, turn on a space heater and run the shower full hot, leave the room and close the door, come back in five minutes and open the door, you'll get blasted in the face with the heat build up as soon as you open the door.....
The reason for wanting this effect in your engine is INTAKE SCAVENGING. For a few degrees of crankshaft rotation at the end of the exhaust stroke and beginning of the intake stroke, both the intake and exhaust valve are slightly open, this is called valve overlap. Overlap uses the speed of the exhaust gas as a "vacuum" to help draw a fresh intake charge into the cylinder, the faster the exhaust gas speed, the more vacuum you have to stronger draw more of an intake charge into the cylinder. This results in an increase in both horsepower and torque.

And if it is applied to the pipe PROPERLY, it looks great!!!