I've tried searching but couldn't come up with any results/posts in regards to my particular question. I have purchased a Hytech replica from the H-T marketplace which has a long tube design. Now due to the extended piping it's recommended to use a test pipe in replacement for a catalytic converter.

What I wanted to know that would it be advisable/bad/good? to have a matching 2.5" catalytic converter joined the collector of the header? I have a 98 GSR and just about the drop in a JDM-R. I would like to keep both oxygen sensors as well. Of course I will be having a custom exhaust made to match.

Any thoughts/opinions/suggestions would be very helpful. Pictured below is the header in which I have purchased.

 

If you use a test pipe, there is no need for the second O2, it only checks to see if the cat is doing its job, so there is no harm (other than a CEL) in removing it.

It would be best to have a cat that matches the tube diameter if you choose to go that route, that really all depends if your a green guy or not.

 

Got the same header and live in the same town... small world. Would you believe I have the same car in the same colour too?!?!?

I've run a test pipe before and don't like because of the odour when idling in traffic. I'll be adding a spun body cat. These are pretty small and won't take up too much space, look at the bottom of the SMSP page:
http://sms-products.com/Converters.html

Magnaflow/Carsound makes these cats as well.

Where will you be going to get this all fitted? I haven't picked a shop yet.

 

slowcivic2k,
I do have a 2.5" carsound highflow cat to pair with the header/exhaust. I am concerned about exhaust fumes/smell and would prefer to be "green" However if mating the cat directly to the collector is going to have an affect on perform I may look at other routes.

stumpyf4,
It really is a small world. I know of a few GSR's in the sauaga area just like mine/ours. I have probably seen you driving around somewhere. Thanks for the link and info on high spun cats, I have seen those already but since I have a Carsound 2.5" I was hoping to use it. I am most likely going to get the exhaust work done at Zorro muffler, heard good things about them.

Hopefully I can get some more light shed on this topic

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 98_gsrteg &raquo;</TD></TR><TR><TD CLASS="quote">slowcivic2k,
I do have a 2.5" carsound highflow cat to pair with the header/exhaust. I am concerned about exhaust fumes/smell and would prefer to be "green" However if mating the cat directly to the collector is going to have an affect on perform I may look at other routes.
</TD></TR></TABLE>

Don't weld to the collector. Just make a separate cat like OEM but just shorter. You may have to shorten the midpipe.

 

I would be getting flanges attached to the cat and then bolting up to the collector. As for the rest of the exhaust I might just get them to make a custom exhaust or modify one if I can find something that is 2.5"