The stock cat is made of two "beds", the one you see when you look down the pipe we will call Bed1, it is about two inches long, then there is a gap, where the secondary O2 sensor sits, then comes Bed2, it's a biggie, about seven inches long.

You can see that Bed1 does all the "catalysis", and the results wash over the SecO2 sensor, no CEL, it's happy. The purpose of Bed2 is so that when Bed1 is gone/usedup/poisoned/broken, you still have years of pollution free motoring, though the CEL will be lit the whole time.

You can also see that Bed2 could be totally removed, it would not upset the sensor one bit, it doesn't and can't monitor Bed2.

I bought a used cat and removed Bed2. Sounds much better, no CELs, shoots flames much more readily, and is ABSOLUTELY undetectable, by an emissions check, a visual check or even a dealer with a WDS computer hooked up!

It is a bit of a bitch to remove, but I like the results

S

V V V V I can't see the difference....can YOU see the difference?

 

show us a picture of the outside

 

Long time no talk !

Is there any performance benefits to this? Or just for the sound ! I would like to do that as well, but don't have the technical know how or tools to do this

 

That's pretty damn funny. How did you reach Bed2?

 

Diy?

 

Yes, I think you've seen the flaw in my technique.....

To reach bed 2 you COULD go thru the resonator with a 30" long drill bit (not too practical!) or the only other access is thru the sensor hole!

This sounds much easier than it actually is.

The sensor access is the same size and thread as a sparkplug hole.....

The removal took custom made tools, modified dental mirrors, hammers, more custom made tools.....it took me three days, tapping away, after work.

Even using bent stainless 1/4" tubing ( the "custom tool" of choice) I screwed up the threads for the sensor (you have to lever on SOMETHING!) and had to chase the threads to shape them up for re-installation.

The outside of the cat stays "factory", it's rusty, normal, stock looking, virtually impossible to know there is anything missing. No pictures necessary.

S

 

I think you're kidding yourself, the reality is bed 1 still has the same number of cells per sq inch, that's the limiting factor WRT flow

 

I don't judge it that way, sound would indicate it's at least "twice" as free-flowing, someone should flow bench one....

The stock cat is actually quite large in area, and bigger than most aftermarket replacements, so the number of holes is way up on even metallic substrate cats, but 9 or 10 inches of ceramic is too much.

S

 

the primary source of restriction will be the first bed, it regulates the flow to the latter bed. The length could be important, but you're assuming it flows worse than the initial bed, especially since you chipped it out rather than cutting it apart and inspecting it.

Flow and sound attenuation are two entirely different things.

A metallic cat having the same cell density as a ceramic will outflow the ceramic because the cell walls are much thinner, thus providing more open space to flow through.

I might be better convinced if you had before/after data to back it up rather than impressions and assumptions

 

so what your saying is if you have a pipe system your losses are equal to the worst restriction in the system and other restrictions don't add to it even if they are almost the same.

 

Hey Broker73! I didn't even notice your post up there (you gotta get an avatar!)- long time no see!

I have a couple of spare cats, when spring arrives I'll 'extract' the second bed of another one, and you can come over, we'll put it on and you can try it for yourself!

Do you have a cat-back, or just stock? Not that it matters, just quieter with the stocker.

Keep in touch -

S

 

I think it would be easier to take a drill bit and weld it onto a 30" Long steel tube and then weld an end on it to go onto the power drill.....so buy two drill bits cut them in half with a grinder. Weld one end on each end of you steel tubing and weld......30" drill. Then drill out the 2nd bed from the far end. Stealth would this work? or does the cat have some turns between bed two and the rear exit point?

 

Sound clip? :-)

 

A typical 2 bed cat does surve a purpose. One bed has platinum and palladium and turns CO into CO2, and HC into H2O & CO2. The other bed contains rhodium which turns NOx into N & O2.

 

Yes, I'm not convinced that your bed2 description originally given is accurate; care to say where that info came from?

My general understanding is that bed2 is typically the main cat and bed1 is there to reduce cold start emissions i.e. pre-cat, though I don't have anything that specifically states this is the case for the RX-8. Hence, my question on were the bed info came from?