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Does anyone have data on the effect of heat wrap on the exhaust header , positive or négative ...
Or no effect at all , there is a lot of opposing théory on the net.
The first thing I will say is that there is nothing inherently wrong with the concept of some form of heat shield or heat insulation on an exhaust manifold/header/turbo manifold. It's normal for exhaust manifolds/turbo manifolds to have a heat shield from the factory, to protect other components from the heat that comes off and to keep the heat from getting into the cabin. Also, more exhaust temperature is generally better for spooling a turbo especially at low rpm where the engine doesn't make so much heat. It's also better for warming up the catalyst on a cold start, but that's not a normal concern area. You could characterize the performance benefit on a turbo engine as small at best, and on a naturally aspirated engine I suspect the performance impact is basically negligible, ie don't expect any gains at all.
Now, if you've got an unwrapped exhaust part heating up your cabin making passengers uncomfortable then some kind of insulation is preferable. Tired of hot floor boards? Consider heat wrap, ceramic coat, or if possible a metal heat shield similar to an OEM part.
Where the controversy comes in is whether the wrapping itself causes a degradation of the part by whatever mechanism. I don't have any special information on that. I've run heat wrapped welded turbo manifolds before, but not long enough to give even a personal anecdote about their durability versus unwrapped. In my opinion heat wrap looks ugly, much worse than unwrapped, ceramic coat, or OEM heat shield. But they may still be functional. Certainly with stock heat shields a lot of heat is retained in the manifold and they still last for many miles.
Raymond has covered the general principle - Pretty much if we can keep the heat in the exhaust manifold we tend to provide more energy to drive the turbo and hence we see an improvement in spool. The reality is that any difference is probably incredibly small and the more relevant gain is reducing temperature in the engine bay and the heat soak that results. I've personally had trouble finding a heat wrap that offers a long life without degrading and falling to pieces. My preference is to have the headers ceramic coated. This also has the advantage of protecting the manifold from corrosion and improves the looks of the coated part.
Thank's for your time and answer.
My question came from a build i did [ JEEP 6cyl. 4.0l + cam + header + porting ]
The intake manifold and exhaust very close on the same side of the engine , i assume it would be benefic to had heat wrap on the
exhaust header to lower the intake manifold temp. for better performance.
With the answer i got , think i did the right thing ...