I agree with Mike, Do not wrap anything around the pipe. Some years ago I used a full tuned pipe in my racing aircraft. The 40 size engine turned 27k and the pipe got hot! The pipe was totaly enclosed and exited the fuselage ot the side above the wing. I will attempt to describe the setup.

I used what is called a pressure cowl. The air entering the cowl was ducted to the engine and forced through the fins by a tube that was a tight fit around the engine. I made a fibreglass tube that enclosed the pipe for its full length 15". The tube had about 3/16" clearance from the pipe all round. I put three strips of silicone on the pipe to hold it in the middle of the tube. The only exit from the pressure cowl was down this tube. So, all of the coling air was forced through the engine fins and over the pipe. It worked perfectly.

Pressure cowls have been around for a long time. Control Line Team Racers have been using them for decades. Even the 1930s original VW bug had ducted air over the engine.

Most pylon racers using tuned pipes now use a totaly enclosed pipe with a full length pressure cowl.

Ed S