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2017 | GT | 6MT
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25 Posts
Discussion Starter · #1 ·
So I've been doing a little reading and stumbled on the CorkSport aftermarket exhaust write up and did a little extra reading as to why the exhaust headers were designed in such a way by Mazda in the first place. I guess due to the high compression it creates a very hot exhaust charge and the length of the individual header tubes was to ensure that the exhaust didn't escape in to any of the other cylinders and potentially pre-heat the incoming intake charge. This got me thinking of how much heat soak (and in turn pressure loss due to the charge cooling and in turn the exhaust gasses dropping in density) that might be happening in the exhaust headers which in turn got me thinking, has anyone gotten the stock headers ceramic coated (ala Jet-Hot) or heat wrapped?

I searched around here and on the wider web and couldn't find anything too definitive in our particular use case and I'm wondering if anyone has toyed with the idea. It'd also be interesting to see if the under hood temperatures significantly change. I know things are engineered to a cost and if Mazda didn't need to do it (much like any company) to save money, they probably wouldn't.

I've never known if it was actually worth it or if it was snake oil for anything except very specific use cases.
 

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6,547 Posts
The headers are designed the way they are because the SA motor needs very efficient exhaust scavenging to work well. That is, the design of the headers draws as much of the spent exhaust gas away from the compression chamber as possible to reduce cylinder temperature and in turn knock potential is reduced. The tube are designed to prevent reversion, keeping exhaust impulses from one runner from traveling back up another and trapping the hot gas in the chamber, again preventing knock.
There is already a heat shield in place. Intake temps with this car are usually at or near ambient already if the car is moving. Not much more you can do there.....
 

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2017 | GT | 6MT
Joined
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25 Posts
Discussion Starter · #3 ·
The headers are designed the way they are because the SA motor needs very efficient exhaust scavenging to work well. That is, the design of the headers draws as much of the spent exhaust gas away from the compression chamber as possible to reduce cylinder temperature and in turn knock potential is reduced. The tube are designed to prevent reversion, keeping exhaust impulses from one runner from traveling back up another and trapping the hot gas in the chamber, again preventing knock.
There is already a heat shield in place. Intake temps with this car are usually at or near ambient already if the car is moving. Not much more you can do there.....
Got it. I suppose I was meaning more in terms of the metal of the headers absorbing the heat and dropping the pressure of the exhaust along the length of the initial runner before it meets the first collector. Although they were probably designed with this in mind and no further improvements on scavenging can be made.

An interesting thought would be what would happen if the pressure remained higher for the length of the first runner (assuming that there was a measurable pressure drop due to the loss of heat being sunk in to the manifold). Would it propagate up the other exhaust runner or would it continue forward and create a greater vacuum. I know the timings are really specific with these things to make these headers work as intended and maybe I'm just being dumb. Just trying to spark some discussion on if there are any merits, if any at all to doing it with an OEM exhaust manifold.
 
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