[AMOR]

How about the stock cats on the ZLE? Are they melting like this also under heavy track use?

[JSH]

I scraped-out my Kooks green cats last week after a little more than two years. They were a mangled whistling mess. Not burnt. Kooks has referred me to their high output cats, but I know nothing about their specs.

[Marozl1LE]

anybody has tested 200 cpsi HJS cats they fall out too ??


I hear nothing good about
arh cats

kooks cats green cats

gesi gen 1 cats

[Z OH 6]

Kooks has a new set of high output green cats available now under part number 22603400.

[ZLRob]

Why not go full tune with E50/ 91 or 93 mix? That should avoid or at least considerably slow down cats melting like that even under track usage.

[Z OH 6]

Originally Posted by ZLRob

Why not go full tune with E50/ 91 or 93 mix? That should avoid or at least considerably slow down cats melting like that even under track usage.

The green cats aren't melting for most people, they are just folding in and clogging. If they're melting then the tune is probably off.

[SATINSTEEL1LE]

Just hammer those "green cats" out and make them offroad. The look is there for inspection and you will appreciate the power and sound.

[JSH]

Originally Posted by SATINSTEEL1LE

Just hammer those "green cats" out and make them offroad. The look is there for inspection and you will appreciate the power and sound.

Exactly what we did. Hammered/scraped them out. It sounds like John Force now. Not for those with sensitive ears.

[Dan82679]

Just bore out the cats and you will still retain a visual state inspection. You will be on full e85 after your port injection so your exhaust will not smell that bad.

[Z OH 6]

Originally Posted by Dan82679

Just bore out the cats and you will still retain a visual state inspection. You will be on full e85 after your port injection so your exhaust will not smell that bad.

The biggest issue is that these cars sound like hot garbage without the cats. They develop a raspy sound that is hard to fix. You can change the exhaust, different muffler combinations, etc, but the they still have a distinct rough sound to the exhaust. With cats, they just sound a LOT smoother and less raspy. Also, adding port injection just to run E85 is very expensive for a lot of people so that may not be an option either.

[Camaro1973]

Originally Posted by Z OH 6

The biggest issue is that these cars sound like hot garbage without the cats. They develop a raspy sound that is hard to fix. You can change the exhaust, different muffler combinations, etc, but the they still have a distinct rough sound to the exhaust. With cats, they just sound a LOT smoother and less raspy. Also, adding port injection just to run E85 is very expensive for a lot of people so that may not be an option either.

I concur. I can’t stand how these engines sound without cats. The cats tend to do the same thing as a good set of resonators.

My buddy has no cats on his and similar exhaust as me and it’s simply just loud noise. When you take that rasp away it’s a game changer. You can hear the engine how it should sound reminds me of the old 454 days running on 12:1 compression

If you take a c6 z06, put same exhaust as a new c7 or zl1 side by side, there’s simply no comparison.

These new gen 2 cats have been great, I am Just not sure if they are going to hold up on my new motor that’s goin in.

As far as port injection, yeah not cheap. I believe my kit was like 6k for the Holley and that doesn’t include install.

[JSH]

To clarify: My green cats were a mangled whistling mess, but not burnt, as I previously stated. Kooks has referred me to their high output cats, but I know nothing about their specs.

[Z OH 6]

Originally Posted by Camaro1973

I concur. I can’t stand how these engines sound without cats. The cats tend to do the same thing as a good set of resonators.

My buddy has no cats on his and similar exhaust as me and it’s simply just loud noise. When you take that rasp away it’s a game changer. You can hear the engine how it should sound reminds me of the old 454 days running on 12:1 compression

If you take a c6 z06, put same exhaust as a new c7 or zl1 side by side, there’s simply no comparison.

These new gen 2 cats have been great, I am Just not sure if they are going to hold up on my new motor that’s goin in.

As far as port injection, yeah not cheap. I believe my kit was like 6k for the Holley and that doesn’t include install.

When I pulled my OG green cats because I was concerned about them failing, I went with offroad pipes and immediately disliked the additional volume and tone, so I added the Magnaflow muffler in the center as many have done which helped with the volume but the tone still wasn't as good as it was with the green cats, but then I got concerned about the flow of the double Y design so I pulled it out and installed a Jones X pipe muffler and the sound got worse, much sloppier and raspy. I had it on the car about a month and now I'm back to my original green cats again and it sounds great again. I bought a set of the Kooks HO green cats which I will swap out with the original green cats when they arrive.

[Z OH 6]

Originally Posted by JSH

To clarify: My green cats were a mangled whistling mess, but not burnt, as I previously stated. Kooks has referred me to their high output cats, but I know nothing about their specs.

They are custom made for Kooks by GESI, I believe they are rated to 500-850hp per bank instead of the the previous green cats 350-500hp per bank. Based on the specs 3" inlet and 4.5" body, 300 cell count, it looks very similar the Gen 1 UHO cats from GESI, PN 85032.