When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Do you have to have a Government Permit to operate an industrial chimney?
This will fly way under that kind of radar screen. More to the point, with stock intake manifold and dual 3.5" exhaust it'll be just like Sir Mix-A-Lot said:
For the same reason that explains the whole project: Because I can. ;-)
More seriously, those cats together will flow enough for the pump gas tune, so there's not loss. They will also knock out 4-5 dB of noise over a broad frequency band. They will clean up the exhaust gasses.
Here's an estimate of how much a (generic) cat will quiet the exhaust:
Finally, it's just an option: they are v-band clamp attached and I can put in straight test pipes whenever downpipe pressure would otherwise get a bit higher than desired. Optimally exercised, options are valuable, right?
On the infinity pipe area: For reference, ignoring the wall thickness, dual 3.5" pipe gas area of 19.2 sqin. The infinity pipe with 6" overall width and 1/2" segment taken out from both pipes will have an area of 17.6 sqin. It's only a 8-9% area reduction after the gas has already cooled somewhat and after the pulses have already combined. My judgment is that it's never going to be a bottleneck in a system that is dual 3.5" upstream of the infinity pipe. And most importantly, it fits.
These photos in a sense document the revenge of the nerds. High school geometry does work in real life! Savor the Wise Owl stamp that you got if you stayed awake and paid attention in the math class! ;-)
In any case, this is a one gentle and well flowing y-merge from the dual 3.5" cat outlets to the 6x3.5" infinity pipe:
The iPhone editor that rennlist uses sucks hairy *******, by the way.
Well, first of all, whatever's in it, that's not a giant bag. That's at most a medium sized bag, given that we're living year 2017. What's inside the bag is a proprietary mix called "Spec 18".