HFC fitment...2.5" or 3"?

bcfromfl · 03-20-2018, 04:29 PM

OK...over the past few weeks, I've learned more about cats than I thought I'd ever need to, by talking with manufacturers, Seb, and a local custom fabricator. Hopefully, someone else will find this thread and not have to delay their exhaust like I had to, waiting for responses, etc.

There are catalytic converters, and catalytic converters. The quality is directly reflected by price. Several manufacturers out there market "HFCs" -- but they are ONLY APPROPRIATE for NA applications!!

In my application, since I'm using the Garageline X and Mid-pipe combo, it's a 2.5" exhaust. I decided on going with GESI cats, but, as stated above, was stuck between the 2.5" or 3" model. It gets more complicated than that. GESI's 2.5" model is designated "High Output," but limited in the amount of heat and pressure it can withstand. The exhaust fabricator I spoke with said that he would prefer working with the 2.5" cat. However, I double-checked with GESI, and they were not confident that the 2.5" HO cat would be able to withstand the demands of forced induction, and recommended I go with the "Ultra High Output" 3" cat instead. (I just called the fabricator again to see if he could work with it, and he said it would be OK.)

I don't know how to link a photo, but the placement of the cats is at the back-end of the X-pipe, just ahead of the flange to the mid-pipe.

BTW, I ordered the Motordyne ART pipes. Knock on wood...all these parts better work nice together!!

Quicksilvers · 03-21-2018, 04:08 AM

If you know for sure you are going forced induction in the future you will benefit from 3” catalytic converters if you have emissions testing and/or inspection to pass. With a supercharger if that is the route you decide to go catless would be your best option to see the best gains. There are some moderately prices catalytic converters or “HFC” for our cars that are good quality and will last. Why are you Choicing this exhaust set up??

03-20-2018, 04:29 PM	#1 (permalink)
bcfromfl Enthusiast Member Join Date: Nov 2016 Location: Youngstown, FL Posts: 256 Drives: 2015 PW Nismo 6MT Rep Power: 9	OK...over the past few weeks, I've learned more about cats than I thought I'd ever need to, by talking with manufacturers, Seb, and a local custom fabricator. Hopefully, someone else will find this thread and not have to delay their exhaust like I had to, waiting for responses, etc. There are catalytic converters, and catalytic converters. The quality is directly reflected by price. Several manufacturers out there market "HFCs" -- but they are ONLY APPROPRIATE for NA applications!! In my application, since I'm using the Garageline X and Mid-pipe combo, it's a 2.5" exhaust. I decided on going with GESI cats, but, as stated above, was stuck between the 2.5" or 3" model. It gets more complicated than that. GESI's 2.5" model is designated "High Output," but limited in the amount of heat and pressure it can withstand. The exhaust fabricator I spoke with said that he would prefer working with the 2.5" cat. However, I double-checked with GESI, and they were not confident that the 2.5" HO cat would be able to withstand the demands of forced induction, and recommended I go with the "Ultra High Output" 3" cat instead. (I just called the fabricator again to see if he could work with it, and he said it would be OK.) I don't know how to link a photo, but the placement of the cats is at the back-end of the X-pipe, just ahead of the flange to the mid-pipe. BTW, I ordered the Motordyne ART pipes. Knock on wood...all these parts better work nice together!! Memphis370Z, Korstix and ZontheRocks like this.

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03-21-2018, 04:08 AM	#2 (permalink)
Quicksilvers A True Z Fanatic Join Date: May 2017 Location: Atlanta, GA Posts: 2,039 Drives: 2017 370z Rep Power: 25463	If you know for sure you are going forced induction in the future you will benefit from 3” catalytic converters if you have emissions testing and/or inspection to pass. With a supercharger if that is the route you decide to go catless would be your best option to see the best gains. There are some moderately prices catalytic converters or “HFC” for our cars that are good quality and will last. Why are you Choicing this exhaust set up??