Hi everyone. I am having some issues with a strong exhaust smell coming ONLY out of my tailpipe.

I blew an ignition coil about 6 months ago and ended up replacing my catalytic converter with a Magnaflow high flow converter. No noticeable exhaust smell was detected until not to long after I put on my Greddy Catback exhaust. Maybe a couple of weeks after I had put the Greddy on.

Now I notice a lot of exhaust smell. I don't have any codes and I have had two separate shops check for leaks. It's coming from my tailpipe only.

Do you think the cat could be bad already??? Wouldn't I get a code if that were the case. Is it maybe the new muffler??? I'm not really sure why the muffler would matter. The exhaust should already be clean by the time it gets back there right??

Also, is it possible to have a bad O2 sensor and not get a CEL? Could a bad O2 sensor be causing the problem??? Thanks in advance for any input. I'd really appreciate some helpful ideas as the exhaust fumes are pretty unpleasant to me.

 

You bought a cat that wasn't designed for the RX-8. The exhaust gas temperatures are much higher than naturally aspirated piston engine cars and will eat through most aftermarket catalytic converters with ease. My guess is that the catalytic converter is deteriorating. If you want one that performs well, buy a stock one.

 

I was thinking that was probably it. I'm not really sure about O2 sensors and how they work. Any idea why I don't get a CEL with all of the fumes coming through the cat???

 

The oxygen sensors work by heating the element to a specific temperature, and using a transfer layer that increases or decreases electrical resistance based on how much oxygen is getting through. With this, the ECU can determine the oxygen content in the exhaust and from there work out things like air to fuel ratio. The rear O2 sensor is used to compare the oxygen content to the front O2 sensor, and it's looking for a difference to determine that the cat is doing it's job.

However, for some reason, the RX-8's ECU can detect a normal working cat and not throw a CEL even if there is no cat in the exhaust stream at all. And if it can not pick it up with no cat, then not picking it up when you have a cat of any type is entirely possible.

 

The magnaflow cats are known to go bad after a few thousand miles. Not able to sustain the high temperatures of the rx8, they melt rather quickly. My guess is the the decay process has already started and thats whats causing the smell. Go with a resonated midpipe if its failing. You wont have a problem again, except for smell.

 

Thanks guys. I guess I'm going to have to bite the bullet and buy an OEM one from Mazda. There goes a $1000. Damn!