Header wrap vs Header coating
From Nissan 350Z & 370Z Wiki
I have heard this question tossed around a few sports car enthusiast websites and decided to do a bit of research on the issue. This deals with the use of heat wrap around the headers vs. having them coated.
Facts: - Heat wrap is used to keep the heat inside of the header and improve scavenging of exhaust gasses. This helps to keep the heat inside of the header and allow for an even, high rate of exhaust gasses.
- Manufacturers of headers will not warranty their products (to include factory warranty) if the header itself is wrapped.
- Header wrap will damage the header beyond repair, no matter what material it is made of.
- When running a lean mixture, you "may" see minimal, if any gains at all. If you are running rich, you will not gain anything at all.
- And most importantly, if you do not mind replacing your headers and gaskets on a regular basis, and love the look of headers wrapped with tape (ugh), then this mod is for you.
Background on header/exhaust wrap. The use of header wrap started on the race circuit, mostly NASCAR, to improve on power gains. After time they figured that changing the headers and that after each race was not cost productive for such a minimal gain, the practice was done away with. Now, they use chemically treated or eclectrical applied treated headers. These include Jethot, Airborn, and others.
Just imagine for the average street car owner/enthusiast, having to replace a set of $700 to $1200 headers each week. You would not have any money to do any other modifications that would be of more benefit.
Proper use of heat wrap would be to use this for protecting fuel and oil lines. Most cars have adequate firewalls to protect the driver from the engine heat so using that as an excuse for wrapping is incorrect.
Headers need to be surrounded by cool air to function properly. When you use wrap you basically are trapping the heat in, and temeratures can almost reach the melting point. You have seen videos of cars on a dyno. Notice how hot the headers get? I saw one where they glowed bright red. Imagine that wrapped up, what would happen to them. I read that some designers and engineers say that the material used for the headers are designed to withstand those high temperatures. This may be true. But when the header is not allowed to cool properly this leads to nothing but failure of the part. It is simple thermal isolation. The headers get the heat source from the engine. The heat on the outside of the header is basically trapped between the wrap and the header, causing a layer of extremem heat to have no where to go except back into the header material itself. Over time, this is amplified and can fatigue the header. Another thing to realize that is over time, header oxidize, losing some material in the process. This leads to lighter and weaker headers. When wrapped this basically speeds up the process.
What works. On a test track circuit with 10 laps using Jet Hot coated and uncoated headers, the Jet Coat headers actually lowered the temperature measured 1" from the header by over 450 degrees.
Jet Coat and other companies use a process which actually becomes part of the material of the header. Example. the header is allowed to cool normally because there is no thermal barrier trapping the heat in (header wrap) but the coating acts like the thermal wrap in that it helps to reduce the amount of heat into the engine bay. Wierd huh? Not really. Plus the corrosion of the headers are reduced, and because the heat is not stressing the metal they last longer. This process is permanent, meaning that it actually becomes part of the header itself.
In Closing, I have explained that manufacturers will not warranty headers if they have been wrapped. Just because a product performs the way it is advertised, it doesn't make it the right thing to do. This is the case with heat wrap. You would be best off protecting the fuel and oil lines with it instead. If you want a true thermal barrier that allows for normal cooling plus protection from heat, have your headers treated inside and out for the best quality protection. Just remember that this is a permanent process, and once done it cannot be undone. And be sure that having the headers coated should be the last thing you do to them, ater ensuring adequate it and any small modifications are done to them. This will save you money in the long run.