Header Wrap - pros and cons?

[Kinan]

I've been thinking about getting headers and was wondering if header wrap was worth the trouble..mainly to keep the engine compartment temps down.
I've heard it can cause the headers to get too hot and the welds to fail but has anyone actually had this happen to them??
Thanks.

 

[cojones]

I've heard it can cause the headers to get too hot and the welds to fail but has anyone actually had this happen to them??

I've heard that they can retain moisture, and facilitate metal deterioration (yep - even with stainless steel tubing, the high temps will do that), and eventually shorten header life. Not an issue with racecars that require frequent engine rebuilds, but might not be OK for street cars,

I HAVE heard some issues with "ceramic coating" on headers... increasing the likelihood of header cracking due to differing heat expansion/contraction rates (ceramic vs underlying steel).

 

[JChoice]

You can use thermal header jackets. These are not tightly wrapped to the header so you don't get any cracking. I have used wrap on my other car for years without any problems.

 

[ChopsJazz]

I have seen other posts on this same topic and I have to ask, "Is your engine compartment temperature really that high? Is it higher than the rest of ours?"

I never knew this to be a problem. As far as I know header insulating wraps or coatings are mainly designed to keep the header tubes at a higher temperature for faster evacuation of exhaust gasses. Any resultant engine-bay cooling was coincidental.

And, check the engine-bay cooling fan on the passenger side wheel-well opening to be sure that its working.

 

[I Grok NSX]

Check out http://www.jet-hot.com/ . I plan to have the headers on my X coated at Jet-Hot when the warranty has expired (on the headers).

I called the rep at Jet-Hot concerning the fact that the Comptech headers were made of Stainless Steel. He told me the coating they use will expand more than the stainless steel will and will not harm the headers.

I'd let you know how it works out when I have the headers done, at Christmas time.

 

[CityofAngels]

Chops is right.

"Wraps" are designed to maintain exhaust gas temperatures. As the gases cool, they become more viscous and velocity decreases causing greater back pressure the more they cool. In the case of the NSX, I don't think the ECU has a sensor for backpressure and you would cause a mixture problem. Anyone know more about this?

Since there are an abundance of heat sources in the engine bay, I can't see the overall temps dropping any useful amount.

 

[Kinan]

I am familiar why header wrap is supposed to work. Hot air is less dense than cool air and therefore encounters less restriction and thus higher velocity through the headers theoretically resulting in greater overall airflow through the engine.

Header temps are in the area of 1000 degrees and are individual tubes which have much more radiating surface area than that of a solid stock exhaust manifold.. A substantial difference which is why headers are a substantial source of additional heat. Most stock exhaust manifolds also have a heat shield that gets removed so yes, underhood temps with headers can get to be a problem.

Since the rest of the engine is closer to 230 degrees it doesn't really factor in here, its always the same temp with or without headers.

I ran wrapped headers on my Integra and easily noticed lower underhood temperatures and don't question their effectiveness. What I did question is whether the wrap contributed to the header welds that failed while wrapped. That question has never really been answered here either way but I was hoping someone had some hard evidence. Hopefully more info will come in.

Since I recently reinstalled my stock airbox, underhood temps are no longer the concern they were. BTW, the car runs better with the stock airbox with quicker throttle response and a little more torque mid to high rpms.
Thanks for all your responses.