Just how hot is the exhaust supposed to be?!

Pre-cat, I measured temps of about 250F and the same at the engine side of the cat. Post-cat though was nearly 800F! And the muffler as well was about nearly 500F, the pipe and muffler were smoking!

Is this wayyy too hot? Or is this proper catalytic function? I know they get hot, but smoking pipe hot? Jesus. The air-pump is set to give downstream air all the time, which I think is proper operating temperature operation anyway... right?

Cats usually run between 450 and 1,600 degrees, which is why they have heat shields and possibly ceramic insulation as well, but generally will run in the 600-1,000 degree range depending on engine rpm and load. The ideal temp for best efficiency is about about where your's is at, 800-850 degrees. They have to be that hot to function, which is why the air injection is needed,,,,,,,,just like a blacksmith with the bellows.
The air pump should pump air upstream for a short time at cold start and then switch to downstream afterwards.
An central mounted (i.e. in front of the rear axle) muffler can be 400-500 degrees depending on the speed and load. At idle, it'll be much cooler than after a blast down the freeway.
I don't think you've anything to worry about.

Only reason I was concerned was it was making the undercoating (rust proofing) on the bottom of the car smoke.. ! LOL I thought goddamn that seems a bit hot.

I don't have the vacuum system anymore that tells the air pump whether to send up or down stream. I guess I could make it happen properly again, but letting the cat take a while to light isn't necessarily a concern of mine lol. Less engine bay clutter!

Dem cat’s do get smokin’ hot.

By the way, don’t park onto of high grass or leaves. It might be the last like you get to drive the before mentioned car.
After a hard run, I have seen catalytic converters be cherry red!


If you line in a state/country that you can replace a three cat system with an older Canadian Y-pipe (or earlier F-body Y-pipe) – or get custom exhaust made, you will reduce the exhaust temperatures a bunch. Maybe even get rid of a lot of the heat shielding under the car, as well. That is not counting all of the underhood plumbing and air pump removal, can sure make the underhood look so much better and you will have removed about 300+ pounds of ballast off of the car.

A bit of work, you might even see what color the engine is, again.
(Hehe, my ’77 is blue and my ’86 engine is the color of (anti-rusting) “oil”)

BudW