Where do you live? You might get lucky and have a local rotard.

 

I am lucky. I have two.

@RXeckless
@wcs

 

So it's P0420 - Catalyst System Efficiency Below Threshold. The dealer's saying everything appears to be in order but now I'm paranoid about driving if the cat is messed up in any way.. I don't want to screw up my engine! I'm asking them for a quote to replace it.. I'm guessing it would be pricey.

 

I guessed correctly.. $2500!

 

$600

https://black-halo-racing.myshopify....onated-midpipe

 

Yep, definitely looking at this, thanks!!

Also, any feedback about this:

TED Direct-Fit Catalytic Converter Fits: 2004-2008 Mazda RX-8 1.3L

 

I have no experience with that unit in particular, but there are basically three known cats that can stand up to RX-8 exhaust gas temperatures for any length of time:

1. OEM
2. HJS (track use)
3. BHR (no track use)

All others are reported to fail rather quickly.

You can sometimes score a used OEM cat in good condition for around $500 to $600.

Typical EGTs run around 1200F, according to Magnaflow. Here is how my 8's EGTs look on a typical 20 miles drive to work in February, with the ambient temperature in the 40s:



Of course, dumping unburned fuel and oil into the cat, causing it to clog, thereby damaging the engine is another issue. Make sure your ignition is healthy, before you install a new cat.

.

 

Many thanks for the very complete response!
Next question then: how to tell if the ignition is healthy, other than replacing the coils, plugs and wires as a precaution? The car has not had any issue starting, hot or cold (lights right up).

 

My car sometimes sounds a little raspy or as if there is a can rattling around when accelerate. Sources have told that is a factory issue, the noise caused by a faulty heat shield that was recalled. I'm not a hundred percent sure but something to look into. Since like most people have bought there cars used and unsure of what has been maintained, it's good to take it the dealer and replace if it has not been already.

 

Thanks, I'm going to get under the car with @wcs in the near future to figure it out once and for all!

 

That would be the MIAC (marbes in a can) issue - it is due to the fact that you have a partially broken catalyst and likely a failing catalytic converter. Act now - only a limited US Federal warranty on the cat. Driving on a failing cat will eventually lead to a rotary engine failure.