2003 Catalytic Converters...or Resonators?? STUMPED...

[2003 PathGrinder]

Hello All!
I am new on here. This is a great site! Glad I found it.

My question for all you R50 PATH-heads is this:

-Why are the catalytic converters also called "resonators"???!!!

This is driving my insane because I have heard them called different things by local mechanics, dealers, and websites. Not really getting a solid answer. (I am in the process of replacing everything including the cats and back.) I bought the parts needed, but need to know what is in front of the "cats". Because ebay and amazon and a few mechs call these parts the "cats" UHHHHG so confused HAHA!

Here is a little picture i edited:

[Towncivilian]

Both sets are converters. The ones closer to the engine right off the exhaust manifold are pre-cats; the ones underneath the vehicle with the braided heatshield are cats too.

[2003 PathGrinder]

Braided heat shield??!! I have never seen that. Where is that located on the diagram I posted? Thank you for the reply

[Towncivilian]

I didn't really mean there is a "braided heat shield", I meant the woven-looking thing you'd find under the vehicle is also a catalytic converter - i.e. it looks like just about every other cat you'd find. I believe the pre-cats cause much of the confusion here.

[Mark Sheriff]

i have a 1999.5 r50 and there is only two cats, a cat will have a sensor before it and after it, there is no o2 sensor after the resonators, there are two resonators after the cats, which is after the o2 sensors, i have removed my resonators and replaced it with straight test pipes and also changed the muffler to a flowmaster, no check engine light so you know for sure its not a second pair of cats
i also removed part number 54168 which is a silencer/muffler also, this made the system sound much better, it did a great job of making the exhaust quiet until i took it out, also with my setup it does not sound raspy

[BubbaFL]

The right arrow in your diagram points at resonators, not catalytic converters.

Resonator is basically an empty tube, and does not serve an emission control purpose (other than having a place for the downstream O2 sensor to screw in, in this case).

[2003 PathGrinder]

Thanks for the reply,
Actually they are not empty tubes. They have the catalyst substrate inside body. So I am assuming they are indeed the converter. They also have the o2 ports. The units to left with the arrow might be the "pre-cats"? Hmmm...

[Mark Sheriff]

they have o2 ports but that's to detect airflow after the cats, there is no o2 sensor after the resonator, making it a resonator, i have pulled these two resonators out and replaced them with a down pipe like this:



this pipe has the port of the o2 sensor to detect airflow after the real cats, the two pipes are resonators after the cats, they are removed from my truck and i have no CEL on, cats have o2 sensors before and after them

[2003 PathGrinder]

I was looking for something like that! Had I known about them before, I would have purchased a set for sure!

-Should I have replaced the "pre-cats" as well?? Hmm....

[Mark Sheriff]

well there are no pre-cats lol, we have regular cats, my cats are 14 years old and i have no issues from them, however if i do have problems with them down the line, i can always gut them out for more airflow and still pass emissions testing, along with the downpipes i showed you and my flowmaster muffler, that would be awesome air flow lol

[PJSnow]

they have o2 ports but that's to detect airflow after the cats, there is no o2 sensor after the resonator, making it a resonator, i have pulled these two resonators out and replaced them with a down pipe like this:



this pipe has the port of the o2 sensor to detect airflow after the real cats, the two pipes are resonators after the cats, they are removed from my truck and i have no CEL on, cats have o2 sensors before and after them

where did you find that? is the exhaust the same on both the 3.3 and the 3.5? and would it fit my 2001 3.5L?

[Mark Sheriff]

bought mine on ebay:
left side: http://www.ebay.com/itm/Front-Exhaust-C ... #vi-ilComp
right side: http://www.ebay.com/itm/Front-Exhaust-C ... 8a&vxp=mtr

for your 2001 pathy:
http://www.ebay.com/itm/Exhaust-Interme ... 51&vxp=mtr
http://www.ebay.com/itm/Exhaust-Interme ... e8&vxp=mtr

i believe yours have to be welded on where as mine was bolt on

[2003 PathGrinder]

I wonder if they make those for my 2003. Hmmm. Too late anyways! lol...

[Mark Sheriff]

for your 2003 you use the same one as the links i posted for the 2001 pathy

[lrwhat]

The 4 cats system is Cal emmisions so theres 2 diff styles depending where you get inspection