No, not the little furry kind. The catalytic converter. I never thought of it until I saw this video (part 1 and part 2) but I'm wondering if gutting the cat will cause a CEL issue. So I'm wondering if anyone here has gutted their cat.

I'm only thinking of gutting the cat because the front element keeps breaking free then snapping the probe off the oxygen sensor and I'm tired of replacing the cat and the sensor all the time. Another video talks about using a spark plug defouler to create a space between the elements and the sensor to keep it from breaking. I'm wondering if either gutting the cat and/or using the defouler would cause false readings and the CEL to come on. The other reason for gutting the cat is so I don't have to deal with the rattle from the lose element. The damn thing sounds like a square marble trapped in a coffee can. So...anyone tried it?

 

Yes it will cause a CEL, when you gut a cat you turn it into a test pipe that just looks like a cat.

ROD

 

^Like he said. You are essentially making a testpipe you will get a cel.

Next, the nonfouler. I'm not 100% but I believe that adding that on top of your factory cat will throw a cel do to the readings being too far apart.
Now the good news. That nonfouler can be used as a cel delete in testpipe applications. I have it on my car have never had anthing close to a problem been running it almost 2 years car has been inspected twice passed both without anything close to a hiccup. I would suggest both gutting your cat and adding 2 nonfoulers between your second o2 and cat. This shouldn't throw a cel and if it does just buy a 70mm tp because I know for a fact that setup won't throw one. You might net a couple hp plus this car sounds awesome with a cat. I promise the smell isn't as bad as people act if you have spent any time at a racetrack or boat launch ramp you are going to be used to the odor.
Good luck and hope this helped.

 

Or you can be responsible and use a high flow cat like the Berk 63.5mm.

-- Chuck

 

A defouler will 100% keep the o2 sensor from being sheared off, and it will also HELP the CEL to stay off (it will prevent code P0420 from creeping up should the cat ever become inefficient)

Adding a defouler to any S2000 with a stock cat is valuable insurance.

On the same token, if you gut the cat, use the defouler to keep the CEL off.

 

so you're saying that you can use a defouler with an oem cat (non-gutted) and it won't throw a cel? would there be enough airflow/readings?

 

It wouldn't "throw off" readings any more than using it on a test pipe.

The ECU is looking for a fairly flat signal from the secondary O2 sensor.

If you have a high/low voltage swing that matches the primary O2 sensor, the ECU will know that the cat is faulty or not present.

The ECU is looking for a high/low signal from the primary sensor as the car goes from lean to rich at (X)HZ.

It is, at the same time, looking for a signal from the secondary o2 sensor that is flattened out (low voltage) in comparison. Low volts means more oxygen. More oxygen means the cat works.

Putting in a defouler will just make the secondary sensor send a relatively low voltage, flat signal. The S2000 ECU is not smart enough to care how flat or low voltage the signal is, as long as the sensor is not totally dead.

06+ ECU's seem to be more sensitive to the level of O2 in the stream, though.

 

damn. i wish i knew this years ago to save my o2 sensor from being sheared off by the honeycomb

 

Get a Berk HFC it comes with the defouler, an oem cat with a broken brick isn't efficient, and a gutted oem cat won't necessarily perform well due to airflow characteristics.

 

And that is how I started thinking about modifying the cat. I thought of gutting it after watching the video but decided instead to have a welding shop weld a brace just behind the front element so it won't sheer off the probe of the sensor. I was thinking of a short piece of angle iron as an L bracket to stop it. He suggested a stainless 1/4 bolt instead, about 2" or so long. He drilled a hole for the shaft of the bolt then welded the bolt to the cat leaving only a small nub. You really can't even tell it's a bolt.

Now I just have to get a new sensor and we'll see how it works.