[Johnnysflooring]

Is a tune needed if headers and green or hi flow cats are added to stock cat back? Had a Borla system on order and am tired of waiting. Any advice would be great!

[bybcous]

Yes, i have that setup on my SS. Will throw s p0174 code

[BMWM.D.]

Originally Posted by bybcous

Yes, i have that setup on my SS. Will throw s p0174 code

You have the Kooks "green cat" option? Because there's a difference between these and Kooks' standard cats or the cats that come with other header systems.

[Johnnysflooring]

What’s the difference in the various cats? Do some not require the tune?

[Blackdevil77]

In theory, you can add long tubes with "green cats" and leave the rear O2 sensors on without throwing a code. I would still recommend tuning, but technically, you shouldn't have to to keep a CEL from coming up.

[BMWM.D.]

Originally Posted by Johnnysflooring

What’s the difference in the various cats? Do some not require the tune?

The "green" cats are a high quality cat made by GESI. In addition to being designed to handle lots of power, I believe they have more cells than a regular high flow cat. This means that they shouldn't throw any catalyst efficiency codes, and should smell less. Both are benefits as far as I'm concerned.

[Evolvedx27]

Originally Posted by BMWM.D.

The "green" cats are a high quality cat made by GESI. In addition to being designed to handle lots of power, I believe they have more cells than a regular high flow cat. This means that they shouldn't throw any catalyst efficiency codes, and should smell less. Both are benefits as far as I'm concerned.

Don't think they make as much power as regular high flow cats. Minimal but just saying.

[BMWM.D.]

Originally Posted by Evolvedx27

Don't think they make as much power as regular high flow cats. Minimal but just saying.

I was saying they should hold up better as they're rated to handle quite a bit of power. Many high flow cats don't hold up to 600+ hp.

There could be a slight power difference, but it wouldn't be anything I'd worry about. The difference between catless and a typical 200 cell high flow cat is almost negligible from the tests I've seen.

[Can'tHave2MuchHP]

A modified LT4/LS9/LSA will chew through high flow and green cats no problem. I've seen it done and it's not a matter of if, but when. Usually you can just say that "Well, I'll replace them every 500 miles" but if they melt and you keep driving it, especially if you track/drag race or just spirited driving, you'll send all the crap that's in the cats all through your exhaust...And now you're in it for new cats and a new cat back.

I originally didn't like the idea of catless, I thought it was too loud and unnecessary. I recommended high flows to a buddy with a ZR1 and used to be a proponent for them on the Vette/Camaro5 forum, but then slowly but surely, guys I knew who went with high flows because they wanted to quiet it down or avoid any smell, melted their cats and at minimum they caught it early and got to replace just a $300+/- set of cats, but a lot of them had to buy $1000-$2000 cat backs too.

And green cats are hardly tougher if they even are than Kooks already high quality high flows. Don't get marketed into thinking you're buying a bomb proof cat.

As far as tuning...Sure you may just be able to get away with no codes, however that doesn't mean your car is running its best or even safely for that matter. Headers are going to drop engine back pressure, you'll likely run lean, especially at WOT. It's not just about ducking an engine code here.

[Blackdevil77]

Originally Posted by BMWM.D.

I was saying they should hold up better as they're rated to handle quite a bit of power. Many high flow cats don't hold up to 600+ hp.

There could be a slight power difference, but it wouldn't be anything I'd worry about. The difference between catless and a typical 200 cell high flow cat is almost negligible from the tests I've seen.

Not sure what the difference would be on a 600+ horsepower car, but on my LS3 powered Chevy SS, I made exactly 400 rwhp with the green cats or "Gesi" cats. Another Chevy SS with identical mods, except with no cats at all, tuned by the same tuner on the same dyno made 408 rwhp.

[Blackdevil77]

Originally Posted by Can'tHave2MuchHP

A modified LT4/LS9/LSA will chew through high flow and green cats no problem. I've seen it done and it's not a matter of if, but when. Usually you can just say that "Well, I'll replace them every 500 miles" but if they melt and you keep driving it, especially if you track/drag race or just spirited driving, you'll send all the crap that's in the cats all through your exhaust...And now you're in it for new cats and a new cat back.

I originally didn't like the idea of catless, I thought it was too loud and unnecessary. I recommended high flows to a buddy with a ZR1 and used to be a proponent for them on the Vette/Camaro5 forum, but then slowly but surely, guys I knew who went with high flows because they wanted to quiet it down or avoid any smell, melted their cats and at minimum they caught it early and got to replace just a $300+/- set of cats, but a lot of them had to buy $1000-$2000 cat backs too.

And green cats are hardly tougher if they even are than Kooks already high quality high flows. Don't get marketed into thinking you're buying a bomb proof cat.

As far as tuning...Sure you may just be able to get away with no codes, however that doesn't mean your car is running its best or even safely for that matter. Headers are going to drop engine back pressure, you'll likely run lean, especially at WOT. It's not just about ducking an engine code here.

Agreed. I think one of the reason the factory tunes on these cars are so rich is to preserve the catalytic converters. As soon as you tune the car, lean up the AFR, the cats are gonna be enduring a bit more abuse.

[Can'tHave2MuchHP]

Supercharged cars are BRUTAL on cats. An NA LS (short of race engines of course) engine wouldn't come close to replicating the abuse a supercharger gives to cats.

Originally Posted by BMWM.D.

I was saying they should hold up better as they're rated to handle quite a bit of power. Many high flow cats don't hold up to 600+ hp.

There could be a slight power difference, but it wouldn't be anything I'd worry about. The difference between catless and a typical 200 cell high flow cat is almost negligible from the tests I've seen.

High flow cats/green cats don't hold up period to 600+ RWHP. The differences between a high flow and catless is not negligible and I don't care what a scientific lab discovered. Put green cats on your car, pulley it and maybe cam it down the road, and you'll be coming back asking for catback recommendations in a few hundred miles.

[Blackdevil77]

Originally Posted by Can'tHave2MuchHP

Supercharged cars are BRUTAL on cats. An NA LS (short of race engines of course) engine wouldn't come close to replicating the abuse a supercharger gives to cats.


High flow cats/green cats don't hold up period to 600+ RWHP. The differences between a high flow and catless is not negligible and I don't care what a scientific lab discovered. Put green cats on your car, pulley it and maybe cam it down the road, and you'll be coming back asking for catback recommendations in a few hundred miles.

What cats do the Hellcats use? They make over 600 rwhp from factory, are they just doomed out of the box?

[Can'tHave2MuchHP]

Originally Posted by Blackdevil77

What cats do the Hellcats use? They make over 600 rwhp from factory, are they just doomed out of the box?

Funny you should bring that up because the reason Dodge stopped at the power they did is because they were melting the cats no matter what they tried. You can look it up. They ended up backing off the power and upped the fuel to save the cats. Every kid with a Hellcat out there immediately does a "Cat delete" on them for a reason, and it picks up a ton of power with a tune because of the pressure.

And I do believe Hellcats eat a lot of cats. No pun intended.