There have been many people who have gotten the cat inefficiency code. Yes it will happen if your cat goes bad but we've also seen it from time to time on high flow cats too. People automatically assume that the cat is going bad. It might not be if it is a high flow unit. I spoke to Chris at Cobb Tuning today and somehow the subject came up but on Subarus. They have the same problems in many ways that the RX-8's do. The biggest difference is that they've learned which ones they need to pay attention to and why some of them appear when they do.

The cat inefficiency code is calibrated to see a certain value. If your cat is plugged up, it'll throw the code. Conversely if your cat flows too good, you can still throw the code. It's not to say it will always happen, but it can and sometimes does. This doesn't necessarily mean that the cat is failing. It just means your cat isn't working within the range of operation that the factory sensor wants. If you have a high flow cat and get this code, your cat apparently does work as advertised. These are issues that the Subaru guys have had with exhaust changes and it sounds all too plausible that this is what happens with the RX-8 as well. This is just the way ecu's work nowdays. The Subaru fix with the Accessport is not to reset the CEL but rather to disable the sensor altogether so you never get it.

If you have a high flow cat and you get this code, maybe you do have a problem with your cat. On the other hand, maybe you don't and it works just fine. The biggest problem is that it may be an inconsistent code. It may show up one random day after not having it. Just thought the info was good.

I think the problem is that theres no easy way to tell if your CAT is working or not. Most likely you have to take it down and look at it yourself just to see if its *gone*. Sometimes that doesnt work either cuz its too dark inside and its all sealed ..... and who would actually go on a sniff test to see if the CAT is doing its job or not :P

if you watch the voltage for the secondary o2 it should be near the middle of its range with little to no movement. if you see the voltage oscillating up and down where it mirrors the front o2, then your cat is inefficient.

so basically if we want to trick the rear o2 sensor we need to install a capacitor inline or something? Or cobb could just release the rx8 version of access port.

Some time back I drove over a good-sized puddle of water and my CEL triggered. It's the same code. I went away after a few days, but now it's back and I can't get rid of it. How can I definitively know whether I need to replace my high flow cat?
Thanks.

I absolutely guarantee you that I have the most freely flowing cat on any RX-8 short of none at all and I've yet to see a CEL

ok i will bite------what cat do you have?
OD