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NA1 vs NA2 Cats

Joined
27 July 2007
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7,381
Location
Denver, CO
I was reading T3TEC's blog today and Mr. Toyoizumi mentioned that the NSX-R and S-Zero mufflers have different internal piping and flow better than the standard muffler. That got me thinking- has anyone checked to see if the NA2 cats have larger diameter piping than the NA1? It seem somewhat reasonable that Honda would increase the flow to address the displacement increase.
 
I don’t remember the difference being significantly different in size. The stock cats are smaller in diameter then the rest of the exhaust though. Especially when adding aftermarket headers and exhaust. I put Random technology cats in my car so the headers, cats, and exhaust all match in internal diameter.
 
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[MENTION=18194]Honcho[/MENTION] - I don't know about piping of cats, but there was a thread that showed the inside of the exhaust (http://www.nsxprime.com/forum/showthread.php/68558-Nsx-Muffler-Cutaway-and-Modify-Pics-Inside!) In the thread, you will see that NA1 (page 1) and NA2 (page 2) internal exhaust pipings are slightly different.

I don’t remember the difference being significantly different in size. The stock cats are smaller in diameter then the rest of the exhaust though. Especially when adding aftermarket headers and exhaust. I put Random technology cats in my car so the headers, cats, and exhaust all match in internal diameter.

Yeah, I knew about the difference NA1 to NA2 from Trev's experiments (I wonder if the "NA2" version was also used on the 97+ automatics?), but I think Toyoizumi was saying that the R and Zero go even further. They do have different part numbers from the standard exhaust of the same year, and are more expensive. Hard to tell with Google translate lol. I am one of the crazy ones, but I like the OEM cats. When I changed my 91 from OEM to high-flow cats, the throttle response got worse due to the loss of backpressure. Even though I sacrifice 1 or 2 hp, I like the throttle feel with the OEM. I was just curious if the NA2 used slightly bigger piping. I'll update this thread when I measure my 92 cats and maybe someone who has a set of NA2 can measure theirs and post.
 
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