Factory catalytic converters: How many CPI?

[TheBrightSide]

How many cells per inch (CPI) do the factory cats have…? I think someone estimated around like 400 CPI per cat (both primary and secondary cats). I was asking because I ran some cheap, generic high flow cats at one point, and those were ceramic core and had 300 CPI. You can find those kinds of generic, universal cats for anywhere from like $30-60 per cat, on places like eBay and other Chinese vendors, like Alibaba or whatever site is popular these days.

I bought some of those cheap high flow cats, in a 3” inch diameter, and had them weld a 3” OD to 2.5” OD exhaust adapter section to it. It basically served as connection pipes for long tube headers (most collectors are 3” inches), and I ran them on some 1-7/8” Speed Engineering long tubes at the time. It definitely quieted down the exhaust a whole lot more than the off-road connection pipes that I had purchased with the headers; but it still crackled and backfired like normal, just less of course.

I remember having a secondary cat delete on the stock downpipes/cats and it actually wasn’t all that much louder, to be fair… And the factory primary cats actually did such a decent job, that only cold starts had smellier exhaust fumes than normal. Granted, the cheap generic, universal cats probably don’t have all of the valuable metals and some other materials that the factory/OEM cat converters have…

[1JEWLDSSRS]

I read somewhere on here that the factory cats were 600 CPI... Most hiflows were around 200-300 CPI..

[TheBrightSide]

Originally Posted by 1JEWLDSSRS

I read somewhere on here that the factory cats were 600 CPI... Most hiflows were around 200-300 CPI..

Holy shit, 600 CPI per cat?? Damn… That sounds restrictive as hell. No wonder doing a secondary cat delete (or gutting them) did nothing on the stock exhaust setup. I was assuming that those were for like older cars, like maybe during the late 1990’s and early to mid 2000’s or something.

Like I was saying though, having high flow cats (200-300 CPI) made the exhaust significantly louder. At one point, I ran 1-3/4 BBK shorty headers to American Racing (high flow) catted downpipes. It was definitely much louder than a secondary cat delete on the stock downpipes.

I currently have 2” Speed Engineering long tube headers right now, and am running some 3” Flowmaster high flow cats. I have a Borla Touring catback exhaust, with an extra x-pipe added into the non-resonated x-pipe mid pipe, which is how the exhaust system came.

Adding the second x-pipe definitely toned down the drone, rasp, and overall volume a bit. I was actually afraid of installing the Magnaflow x-pipe muffler, as I thought it would have fitment issues and be way too quiet for my taste. And as for something like a Flowmaster dual inlet/outlet (mid) muffler, I felt like it might make the exhaust sound “tinny” and create more drone. Wasn’t too sure, although I might make another custom dual H-pipe or some other custom mid pipe to test out. These aren’t fairly popular exhaust setups for the 5th gen Camaro V8, so I figured I’d experiment…

[1JEWLDSSRS]

Originally Posted by TheBrightSide

Holy shit, 600 CPI per cat?? Damn… That sounds restrictive as hell. No wonder doing a secondary cat delete (or gutting them) did nothing on the stock exhaust setup. I was assuming that those were for like older cars, like maybe during the late 1990’s and early to mid 2000’s or something.

Like I was saying though, having high flow cats (200-300 CPI) made the exhaust significantly louder. At one point, I ran 1-3/4 BBK shorty headers to American Racing (high flow) catted downpipes. It was definitely much louder than a secondary cat delete on the stock downpipes.

I currently have 2” Speed Engineering long tube headers right now, and am running some 3” Flowmaster high flow cats. I have a Borla Touring catback exhaust, with an extra x-pipe added into the non-resonated x-pipe mid pipe, which is how the exhaust system came.

Adding the second x-pipe definitely toned down the drone, rasp, and overall volume a bit. I was actually afraid of installing the Magnaflow x-pipe muffler, as I thought it would have fitment issues and be way too quiet for my taste. And as for something like a Flowmaster dual inlet/outlet (mid) muffler, I felt like it might make the exhaust sound “tinny” and create more drone. Wasn’t too sure, although I might make another custom dual H-pipe or some other custom mid pipe to test out. These aren’t fairly popular exhaust setups for the 5th gen Camaro V8, so I figured I’d experiment…

Yep. And I just read this in another post on here today where a member said the same thing. That Magnaflow mid muffler/x pipe fits in there just perfectly, but might tone down the sound quite a bit. I had one before I did the Corsa catback. You sound like me, I did about 8 different "Frankenstein" exhaust setups until I pulled the trigger on the Corsa, which I should have just done in the beginning. lol.