Bought the car with headers all the way back to a giant catback

[sc2dave]

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.

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.

[sc2dave]

Here's more ;If the mix is too lean, the converter won't have the right elements to clean the exhaust. Too rich and the converter will heat up to the point of melting, and trying to push exhaust through a solid block is tough. If your car burns oil or leaks coolant into the engine, these contaminants can collect on the ceramics inside the converter and cause it to clog. TOO RICH kills it. from http://autorepair.about.com/od/gloss...catalyti_2.htm

[sc2dave]

Here's one from wikipedia ;Meltdown

Any condition that causes abnormally high levels of unburned hydrocarbons — raw or partially burnt fuel — to reach the converter will tend to significantly elevate its temperature, bringing the risk of a meltdown of the substrate and resultant catalytic deactivation and severe exhaust restriction. Catalytic converter - Wikipedia, the free encyclopedia

[sc2dave]

Originally Posted by Ladogaboy

I'm sorry, but I'm going to have to default to what I have been told by professional mechanics and aftermarket tuners.

Tell them to read this thread,the "pros" might want to learn something.

[Ladogaboy]

sc2dave, you obviously have a limited perspective. My point was only that increased EGT can damage a catalytic converter. The fact that other factors can also damage a catalytic converter has no bearing. The truth is, if you give me a lift and a ball peen hammer, I can destroy just about any catalytic converter too. That doesn't mean that there aren't also other methods.

It just so happens that increased EGT are more pertinent to this particular thread. But, by all means, persist in your belief that only fuel burning in a cat will cause it to fail.

[sc2dave]

Ok then. Show me some articles where just adding headers can destroy a cat.

[Ladogaboy]

Originally Posted by sc2dave

Ok then. Show me some articles where just adding headers can destroy a cat.

*sigh* Again, you seem to have missed the point. I specifically said the combination on a lean-burning engine might cause the EGT to rise high enough to damage the cat, but you are hell bent on making the point that ONLY a rich AFR will harm the cat. The fact is, there are many ways to kill a cat; I was only attempting to point out a possibility for this particular situation. Mixing and matching exhaust components has the potential for unwanted effects; I was merely attempting to point out one of those concerns.

Regardless, it seems the OP is done with this thread, so I'm done arguing the point with you.

[sc2dave]

If high egts kill cats,then why do the oem's install pre-cats,INCHES away from the exhaust valve? I guarantee no header is going to make it run hotter than that on a cat about 3-6 feet away from the ex. valve.

[pana]

I would find a stock Civic VX or HX manifold which are both designed for an engine that maximized MPG's. Swap the muffler for a stock CRX SI for a more pleasant cruise. My stock CRX Si was getting 38 mpg in mixed driving (70% freeway 30% city). Hope this helps.