Quote:
Originally Posted by Ladogaboy
A typical exhaust manifold is cast out of iron, which means two things: One, it has more mass, meaning it can absorb more exhaust heat. Two, the stock exhaust manifold has a larger surface area, meaning it disperses the heat better. Headers have possibly 50% or less mass than the OEM manifold, and, while they do flow better, that only means that the hotter exhaust gets to the cat even faster.
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If an exhaust manifold is a lot thicker,it's going to contain more heat inside.I really think that egt's would have to be many hundreds of degrees more for it to damage the cat.If that's true,why don't cats get damaged right away when someone does full throttle runs with cats? Because the heat isn't what kills them.Unburned gas being lit with the hot cat catalyst does.