# Performance Catalytic Converter for B13 GA16DE



## bodjprime (Aug 22, 2014)

Hi Guys Newbie Question,

i was wondering if we have a Performance Catalytic Converter for our B13 Sentra with a GA16DE


----------



## Hookah (Nov 3, 2015)

I have only heard of universal high-flow cats, other than cats that come with complete exhaust system kits. Just get the size that matches your pipe or the size of pipe that you are having installed with the cat. I have seen high-flow cats on Ebay for various sizes of pipe. Performance websites usually sell them too.


----------



## bodjprime (Aug 22, 2014)

Hookah said:


> I have only heard of universal high-flow cats, other than cats that come with complete exhaust system kits. Just get the size that matches your pipe or the size of pipe that you are having installed with the cat. I have seen high-flow cats on Ebay for various sizes of pipe. Performance websites usually sell them too.


I see, so universal high-flow cats, and yeah i saw something that looks like a exhaust headers with cats, its like a 4-2-1 or 4-1 and then a cat on the end


----------



## Hookah (Nov 3, 2015)

Coincidentally, I have started researching high-flow cats so I can finalize my exhaust system. While searching for one of your own, keep these things in mind.

The main aspect of a cat's flow is the "CPI" (cells per square inch) of the internal "brick"... the lower the number, the better the flow, and the louder it will be, and generally the less it will clean the exhaust. 300 CPI or less is considered "high-flow". I measured my stock B13 GA16DE's brick at 400 CPI, which is supposedly good for a stock cat, but not necessarily high-flow.

There is also the difference between a metal substrate and a ceramic substrate. Metal bricks may flow better than ceramic bricks, however the comparisons I have seen have been between bricks with different CPIs along with the different materials, so it might just be that the metal bricks are more often used for lower CPI. That being said, lower CPIs/higher-flowing cats are more likely to be metal than ceramic, which might be a clue to use in your decision if other details aren't available.

Another aspect is the length of the brick, as the longer that the gasses are in contact with the brick, the longer the gasses are having to fight through that restriction. The stock GA brick is nearly 6 inches long.

Yet another aspect is the surface area of the face of the brick, with a larger area having more cells to allow air through. The GA brick is 3x5 inches, oval. However, I would think that too large of a cross-section might hurt velocity, but that's only a possibility.

Also, there is the size of the inlet. Of course a larger inlet will be less of a choke point than a smaller one. The GA inlet is between 1.5 and 1.75 inches. Going to a 2 inch opening with a 2 inch pipe should promote better flow in this example.

The final aspect is the flow characteristics of the casing. "Spun" cats seem to flow better than conventional cats of the same specs, with some comparisons making that assertion, though not as much evidence as I would like. This might be due to the spun cats having a round brick and gradual slopes, which could encourage flow more than the asymmetrical design of a conventional case. A 4 inch round brick has only slightly less surface area than a 3x5 brick.


...
I ended up buying a Thunderbolt spun cat, but before all of this research, only after anecdotal reviews and exhaust videos for sound comparison, so it ended up being 400 CPI like my stock cat. I remain hopeful though since the brick is an inch shorter, the case is spun, the inlet is larger, and reviews say it is louder than stock which is a sign of higher flow (though different vehicles introduce an additional variable), and my stock cat is 24 years old. At the same time, I do need all the anti-rasp components I can get, which is a characteristic of cats, as well as reducing the volume from being catless (but louder than stock), and deeper than either catless or stock. Combined with my other more carefully chosen components, I hope to get the desired sound and flow rates.


----------



## Hookah (Nov 3, 2015)

I made another observation. The stock cat has a ring around the outer edge of the brick face that covers 5 rows of cells, about 1/4 inch, effectively making the surface area 2.5x4.5 instead of 3x5. I'm not sure if this is a feature of all OEM cats, but the Thunderbolt cat doesn't have this, meaning the 4 inch round brick actually has more available surface area than the stock cat.

If you want to know if a high-flow cat has this ring of blockage, be sure you can see the very edge of the face of the brick in pictures.


----------

