hey all, i recently bought the HFC's from Kinetix how ever i see that my current stock exhaust seems to have 4 cats and these look to only replace the first 2. if this is the case what options do i have to replace the second pair of cats besides a new cat-back exhaust? somthing that would fit with these new kinetix HFC's and my stock exhaust.

i have not yet installed these kinetix HFC's.

https://www.maperformance.com/collections/exhaust-components/products/kinetix-racing-high-flow-cats-350z-g35


yes im a n00b.

Thanks!

 

You are probably mistaking the resonator for a second pair of cats. The piece that's between your O2 sensors, that's the catalytic converter. Has bolt flanges on both ends of the pipe.

 

Hello OP, it is important to get to know your car, especially the basics. Simple google search will do the trick. There are only 2 cats, like cleric says the other pair you saw are resonators. In this pic, which are Art pipes, they are designed with huge resonators that you are seeing closest to the tranny.

 

Yes, what you have is normal. HFCs replace the restrictive 4 cats in the OEM system with just the 2 before the sensors. It's one of the main reasons they are such a performance improvement!

Some other HFCs you may find on the market are called "resonated" HFCs. This means there's a small resonator after the cat, it's supposed to help with rasp, but with a matching cat back exhaust they're not really necessary.

 

What do you mean by "matching"?

 

​​​​​I'm referring to matching pipe diameter. Most of the time, rasp is caused by going from large pipe into smaller pipe.

Most HFC and test pipes have a 2.5" diameter, stock y-pipe is only around 1.75" or 2". So usually installing a HFC or test pipe with stock exhaust will cause some rasp.

 

So then in theory, if I were to buy FI Resonated HFCs https://www.fastintentions.com/produ...roducts_id/111
they're 2.5, so as long as I get a 2.5+ in diameter y pipe (which goes into an equal diameter/wider exhaust) then I should be OK?

I haven't heard your theory before so forgive me for being skeptical - are you pretty confident about it?

 

I have AAM HFCs and Fast Intentions cat back exhaust. No rasp and car sounds amazing.

Check out old posts in the exhaust compilation threads for other experiences of rasp when using hfc/test pipes and/or y pipes with stock exhaust. One guy even went as far as making a cone insert for his y pipe to match the mid pipe diameter to get rid of rasp.

 

I saw your youtube vid of the setup, sounds nice. How was the quality of the AAM, I read there's fitment issues sometimes?

PS, know anybody selling a used FI catback? :P

 

Didn't have fitment issues. No issues so far after 160k miles or so.