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What do you guys think about insulating extractors/headers? I had a set of extractors made up last year in stainless steel. I was going to get them ceramic coated, but the budget let me down again!

They get really hot and I've noticed the under bonnet temperature is definitely higher than with the old cast iron manifold.

What do you think about wrapping them in that insulating fabric/fibreglass stuff? I assume the temp will be down a bit. What about performance gains?

Cheers

It will help by both reducing the engine bay ambient temperature and by increasing exhaust flow by retaining heat inside the header. This raises exhaust temperature thus lowering its density, and as a result it flows more easily. Same overall mass flow rate, but with less resistance.