Supercharger and high flow cats

[Pearlj10]

Thought I’d share my experience. I installed a stage 1 Overkill supercharger one year ago and had already installed BBK headers, their HFCs, and Corsa exhaust. I haven’t driven the car even 1,000 miles in that time, in part due to fueling issues and getting a decent tune to drive safely, but decided to remove and inspect the cats yesterday. What I saw is summarized in the first picture below. Yikes.

I had read that cheap HFCs and forced induction don’t pair well, and talked to Will @ Overkill prior to purchasing the SC. Will thought the tubes of the BBKs might be long enough to dissipate heat and not melt the cats. Logical thinking but it didn’t work out that way. Several on this forum rightfully said “ditch the cats!” But I live in Phoenix and needed to comply with emissions inspection. Well, that was before they failed me for OBDII tampering (tune) and I decided to register it in another county w/o emissions inspection. I welded 2.5” tube inside the gutted cats yesterday (in case I need to comply with inspections in the future) and will reinstall today. No more worrying about the damage a melted cat may cause. I’m really glad I caught this when I did.

[Pearlj10]

Melted cat in picture above was passenger’s side. Here’s how the driver’s side looked. Beginning to melt in the middle, I believe.

[BatmaroBeauty]

Holy shhhh** thats nuts! I have ARH longtubes and when I purchased them, I was on the fence about getting them with no cats or getting the HFC for the same reasons you stated as its a requirement to pass for NYS annual inspections. I also heard talk of the Bosch ECU not being able to ghost tune for catless pipes. I ultimately decided to go no cats despite those hurdles because of the benefits for FI and just deal with the headache every year of trying to pass inspection. I guess thats arguably a better headache than having melted cats.

So you completely gutted the cats, did that allow for you to pass emissions for your state? In NYS they hook it up to a computer to get readings so just having the appearance of cats alone wouldn't be enough to pass unfortunately

[Pearlj10]

I completely gutted the cats and welded in tube so there wouldn't be a balloon/turbulence in exhaust flow. I registered the car in a county that doesn't require emissions, using my mother in law's address . I'm guessing the car burns clean enough to pass the sniff test, which is my frustration in Maricopa County, AZ. All they care about is if you modded the car, not if it actually burns clean. Go figure.

[BatmaroBeauty]

Ahh I see, wanna register mine there for me too? hahaha

Was there a noticeable difference at all in the exhaust note after they got gutted?

[Pearlj10]

Not much of a noticeable note in exhaust tone. If anything, it might be a tad quieter. I was expecting the opposite. No gas smell that I’ve noticed yet, either.