If you have a subscription to Motortrend+ you might want to check out this episode of Engine Masters: https://www.motortrend.com/plus/deta.../5209849/30774

To summarize they tested various heat barrier materials on a piece of 22 gauge sheet metal place next to a header that was producing 960F heat for 30 seconds. Not all of the materials worked very well and a couple of them were worse than the bare sheet metal baseline test. The conclusion was that insulation that was multiple layers and or incorporated some air pockets worked the best. The fancy gold stuff was not good at all.which is a bummer because it is soooooo pretty.

They also tested three types of header wrap. All of them cut header heat about 150F with no difference in the type or wrap used. In the past they have tested header wrap to see if it adds power, which is a claim that header wrap manufactures have made since this stuff was introduced. Their testing showed absolutely no HP increase from the use of header wrap.

My conclusion from their testing is that if you use the right insulating material you are better off insulating the stuff you want to keep cool. So the air box, intake manifold, floor above the exhaust, header heat shields, etc. Wrapping the header is going to knock down a portion of the heat but not as much as insulation applied strategically around the exhaust.

 

interesting!
and for sure its ok to insulate the cold part instead of the hot part, it seems like its a little out of the box thinking, but it shouldn't be.

 

Engine Masters is one of the best shows on TV!

 

Aren't you at Lake Garnett this weekend?

 

Unfortunately no. Family emergency came up early Friday so not able to go. Next year I guess.

 

Header wrap 100% works , I never bought the increase HP claims but the amount of heat is noticable .

 

Hotter exhaust moves faster, and in the case of the RX-7 this should improve scavenging (or spool on a turbo motor). A long primary N/A header would probably benefit the most from heat wrap.

Of course it all relies on the exhaust tuning. I suspect in most cases, your standard header is probably tuned for modest exhaust temperatures. If you're racing at a high level and can keep the exhaust together, you are definitely going to have a power advantage with a hotter exhaust, assuming it is designed/tuned properly.

Check out 2 stroke race stuff, they often have a hot button on the handlebar to preheat the exhaust before a race. Scavenging has far greater benefits on a 2 stroke/rotary vs. a 4 stroke, just look what happens when you swap out a log manifold to an RB header.

 

Huh, I have used the gold stuff (DEI is local-ish and we could buy at dealer pricing) to insulate plastic HVAC cases from header heat with good results.

I have a couple hundred dollars worth of it to insulate the floor of the R53 I am working on.... the short version is that it has a Subaru drivetrain, for ground clearance the 3" downpipe has to run next to the transmission, which meant I had to modify the floor a lot (more) to clear the pipe, and because of both the way the Mini floor is structured and the need to have foot well room for the passenger, there is only about 1/2" of clearance from the pipe to the floor. No air gap possible...