[Wuiquen]

Ok. I am asking because I have searched and nothing good came up.

Why does the SC blow up high flow cats with headers but have no problems with the 4 OEM cats? Why does Kooks sells a dedicated SC application cats but most if not all headers sell systems with cats that work for the SS and the ZL1? What is the secret here that i am missing out? I am ordering the catted connections to a set of AR headers but will those cats last on the ZL1? Is it better to order the Green cats from Kooks?

I have seen post on the Corvette and the CTS V sites about melted cats, clogged cats, issues with cats and SC. Is this similar to the LT4? My goals aren't to push that much power. I am probably getting the headers on, plus the Roto-fab and maybe a ported TB, then tune. Probably no other major.. ohh yeah Flex fuel E85 maybe if i can wrap my head around that.

Thanks for any input

[Spaceme1117]

Its probably a combination of things.

FI engines just pump more unburned fuel through cats in general and so heat them up to high temps.

And all high-flow cats I have ever seen are using what looks like a rolled type of matrix for cats; not sure how they are made but they don't look anywhere near as durable as the ceramic matrix that is in a factory cat.

[d15b7]

^ what he said. it’s important to understand that a forced induction car has to run richer when under high load conditions (such as tracking it) in order to avoid detonation vs a NA car. Richer = more unburned fuel in the exhaust which = more heat in the cats. The OEM cats are designed and tested for this by the factory. My guess is that the after market companies aren’t testing as rigorously or spending as much in research and testing as the factory.

[hawk02]

Originally Posted by d15b7

^ what he said. it’s important to understand that a forced induction car has to run richer when under high load conditions (such as tracking it) in order to avoid detonation vs a NA car. Richer = more unburned fuel in the exhaust which = more heat in the cats. The OEM cats are designed and tested for this by the factory. My guess is that the after market companies aren’t testing as rigorously or spending as much in research and testing as the factory.

Please explain how unburned fuel in the exhaust makes the cats run hotter? I thought the whole point of the cat over temp (COT) protection in the stock tune is to add more fuel and thereby make the engine run really rich to help cool the cats. No question detonation will overheat the cats but unburned fuel? What am I missing here?

[synolimit]

cause they are all Chinese junk. i love Vibrant as a company and to get exhaust parts from to make what ever but the stuffs still Chinese.

[clg82]

That begs a good additional question, how much HP are the stock 4 cats good up to?

[Camaro1973]

Originally Posted by Wuiquen

Ok. I am asking because I have searched and nothing good came up.

Why does the SC blow up high flow cats with headers but have no problems with the 4 OEM cats? Why does Kooks sells a dedicated SC application cats but most if not all headers sell systems with cats that work for the SS and the ZL1? What is the secret here that i am missing out? I am ordering the catted connections to a set of AR headers but will those cats last on the ZL1? Is it better to order the Green cats from Kooks?

I have seen post on the Corvette and the CTS V sites about melted cats, clogged cats, issues with cats and SC. Is this similar to the LT4? My goals aren't to push that much power. I am probably getting the headers on, plus the Roto-fab and maybe a ported TB, then tune. Probably no other major.. ohh yeah Flex fuel E85 maybe if i can wrap my head around that.

Thanks for any input

Search, my posts. I've burned through 3 sets of gesi gen 1 kooks cats.
They don't melt, the material gets pushed in (flattened).


Gen 2 cats seem to be holding up. I'm actually going to crawl under there today and scope them.

[Wuiquen]

Originally Posted by Camaro1973

Search, my posts. I've burned through 3 sets of gesi gen 1 kooks cats.
They don't melt, the material gets pushed in (flattened).


Gen 2 cats seem to be holding up. I'm actually going to crawl under there today and scope them.

Do you think that is due to the additional power you are putting thru the system? or should I expect the same type of failure from most high-flow cats out there. in my case, it would be AR cats but I have heard, they just get Kooks cats and weld them into their system. I dont know if this is true or no.

Also, do you track your car a lot? I probably wont be tracking as much. Maybe once every quarter or even less.

I wonder if I can get a set of secondary factory cats from someone used and have those weld in the exhaust? i understand they arent high flow.

Are the OEM cats for the ZL1 different than the SS?

[JSH]

I need to check my Kooks green cats to see if they're still alive, which I doubt.

[airtroop01]

I am probably one of the few pushing this supposed ticking time bomb to the limit… being that I’m at 808rwhp on the factory headers and all 4 cats.

Part of the issue is most tuners will lean out the A/F which will net you a better dyno number. The mind set has always been that too rich of a mixture and you burn the cats up.

Actually, the reverse is true. A richer mixture leaves a little ponies on the table and results in cooler cylinder temperatures and therefore a cooler exhaust temp and therefore saving your cats.

It’s possible to do… after all the high end cars like Bugatti managed to do it.
Most of us just chuck the exhaust in the bin in lieu of long tubes and free flowing pipes to let the bald eagles fly. Just takes a few crazy nuts like me to try a different path and see another way to skin this “cat”

[Camaro1973]

Originally Posted by airtroop01

I am probably one of the few pushing this supposed ticking time bomb to the limit… being that I’m at 808rwhp on the factory headers and all 4 cats.

Part of the issue is most tuners will lean out the A/F which will net you a better dyno number. The mind set has always been that too rich of a mixture and you burn the cats up.

Actually, the reverse is true. A richer mixture leaves a little ponies on the table and results in cooler cylinder temperatures and therefore a cooler exhaust temp and therefore saving your cats.

It’s possible to do… after all the high end cars like Bugatti managed to do it.
Most of us just chuck the exhaust in the bin in lieu of long tubes and free flowing pipes to let the bald eagles fly. Just takes a few crazy nuts like me to try a different path and see another way to skin this “cat”

The factory cats though are actually better then most aftermarket cats. Im not sure i would want to push 800rwhp through them though.


I scoped my gen 2 gesi cats again today and they are still perfect.

[jaybee924]

Originally Posted by airtroop01

I am probably one of the few pushing this supposed ticking time bomb to the limit… being that I’m at 808rwhp on the factory headers and all 4 cats.

Part of the issue is most tuners will lean out the A/F which will net you a better dyno number. The mind set has always been that too rich of a mixture and you burn the cats up.

Actually, the reverse is true. A richer mixture leaves a little ponies on the table and results in cooler cylinder temperatures and therefore a cooler exhaust temp and therefore saving your cats.

It’s possible to do… after all the high end cars like Bugatti managed to do it.
Most of us just chuck the exhaust in the bin in lieu of long tubes and free flowing pipes to let the bald eagles fly. Just takes a few crazy nuts like me to try a different path and see another way to skin this “cat”

Dude what's your setup? I have corsa double helix with their Corsa NPP mufflers. I don't want to give up the X-pipe or hack it up to fit long tubes. I have some CA Performance pipes but when I go get the cam put in I don't want that smell from a catless system. So I'm thinking of the path I want to go.

I normally do headers but I don't know if I want to do it on this car cost and everything else. The Corsa NPP Xtreme+ sounds great and loud with just the two primaries don't want to make over the top loud with long tubes or now possibly with deletes. Nothing wrong with a loud car but I don't want to draw too much attention. LoL

I'm a year out at least when I start but plan:
Cam (Tuner recommendation)
IW balancer with 9.1 lower
LT5 Throttle Body with adapter
CA Performance pipes (idk, but if not then may go Flex fuel kit) or pending if I find catted headers at a steal

Car already has:
Roto Fab standard with Dry Filter
Corsa Xtreme NPP+ with double Helix X-pipe

I'm not racing or anything just my fun little car with more added power.

[airtroop01]

Originally Posted by jaybee924

Dude what's your setup?

Magnuson 2650, toohighpsi fuel injection plates, cordes low side, RotoFab big gulp, 103mm snout and NW TB… Borla catback… and e85.

Similar setup to what Mike at Toohighpsi is running but he is pushing 900rwhp through the cats on his z06 if I recall correctly.

Mine is street driven 99% of the time with the occasional open track session if it works out with my schedule. Short distance to work but flogged daily on a few areas on my route so it’s not babied at all. I have not yet track tested the new setup as I planned to fine tune some manners with my tuner but I have not had enough runway to do that here without cars in the way.

If it wasn’t a pain in my state, I would run long tubes, high flow cats and a pair of resonators to keep the noise down some so street driving and having people in my car (work) isn’t a pain. I still may go that route but for now I am going to get there with this setup as it’s working out exactly as I hoped.

[Spaceme1117]

Originally Posted by hawk02

Please explain how unburned fuel in the exhaust makes the cats run hotter? I thought the whole point of the cat over temp (COT) protection in the stock tune is to add more fuel and thereby make the engine run really rich to help cool the cats. No question detonation will overheat the cats but unburned fuel? What am I missing here?

The cats convert excess fuel into inert exhaust gases using the platinum and palladium and in the process generate a lot of heat. It just how the chemistry works. Most chemical reactions have an ideal temperature where the reaction is the most efficient.

Ever wonder why every car made in the last 30 years has a high and a lot of times an air injection pump that is used right a cold start for about a minute or so? The factory tune is injecting extra fuel and air to get the cats up to a temp where they are the most efficient. It is using the heat from the catalytic reaction to elevate the temp to the most efficient point to lower emissions for the rest of the trip. Its somewhat ironic, that to lower emissions the car create high emissions at first.

I'm not sure at what point adding more fuel quenches that process and cools the cats, so I would think that a tune would need to be dialed in for protecting the cats and every tuner does things differently.

The other thing is factory cats have a lot high density of substrate and so can absorb a lot more heat.