What about ceramic or other heat wrap coating? Though there are pros and cons to heat retention treatments with exhaust components, the general consensus with headers is that heat retention benefits outweigh the liabilities.
Pros:
Increased heat retention, which is beneficial for exhaust flow.
Reduces underhood temps, which decreases IC heatsoak.
Cons:
Additional expense.
Additional lead time, in the case of coatings.
Increased heat retention, which in some cases, can accelerate metal fatigue, especially at weld joints.
No proven HP increase.
If you plan on using a coating, ensure you are aware of what impact this will have on your header warranty if applicable. Coating or wrapping your header can void exhaust component warranties. If using a ceramic-type coating, ensure it’s working heat range is above the known EGT. EGTs can be as high as 1400-1600 degrees in the extremes. Some normal coatings are not rated to this temperature level.
What types of ceramic or other heat wrap coating are available? The two most popular manufacturers of heat wrap are Thermo Tec and DEi. The two most popular coating manufacturers are Jet Hot and Swain Tech Coatings. Wrapping is a DIY project with a shorter life span than the professional only coating with a longer life span.
Buy a Thermal Uppipe Blanket here:
Do I need an EGT bung? No. The EGT bung is there for one purpose. It houses the EGT probe that monitors the exhaust temperature so the engine heat does not break down the catalytic converter element if the EGT becomes too hot. Since your new uppipe has no cat, you don’t need an EGT probe.
My uppipe has an EGT bung, should I plug it or reinstall the stock EGT sensor? There is a chance down the road that EGT probe could burn up and pieces of it could be ingested by the turbo. Plugging it is the best option. You will need a M12x1.25 bolt. They can be tricky to find and many go to auto parts stores and ask for this type of oil drain bolt. True hardware stores are also a good place to find these. You may consider a jam nut if the bolt is too long, or you could trim it down to fit better. High temp thread locking compound is also an option.
What is the CEL fix? 2.2 KOhm 1/2 watt resistor. These are available at Radio Shack and are usually in stock. $1 buys you 6 of them. You place it in the EGT connector, which is the bottom connector just forward of your passenger side strut tower. It only has two holes, so jam one end of the resistor into each. If you do not use this resistor, you will probably end up with the CEL code P0546 = Exhaust Gas Temperature Sensor Circuit Malfunction (High Input). ***NOTE***There are two CEL fixes for the WRX, the other one is the rear CEL code P0420 Catalyst System Efficiency Below Threshold, this code being caused by the lack of a catalytic converter in the downpipe. This is usually fixed with an electrical fix or mechanical fix. This notice, though not important to this thread, acknowledges there are two “CEL fixes” and defines them individually to avoid possible confusion.
CEL fix location is forward of the passenger side strut tower:
Should I reset my ECU after this mod? It is never a bad idea to perform an ECU reset after a mod. The traditional route is to disconnect the negative battery terminal, press the brake pedal for a few seconds to bleed the system of charge, and reattach. Some use the more advanced Vishnu Reset.
What about emissions problems like emissions tests and legality? The main purpose of the uppipe cat is to keep cold start emissions low until the main catalytic converters warm up. Using a catless uppipe is a violation of section 203 of the Clean Air Act. Each state has statutes that cover this subject as well. There have been no know reported cases of catless uppipes causing state emissions test failures.