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High Flow Catalysts

 
Old 02-03-2019, 07:16 PM
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ESBESQ
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Default High Flow Catalysts

What's the newest/best hi-flo catalytic converter for a supercharged LS6, making over 700hp at crank, that'll still trigger the OBD II cat monitor?

I was running two C6 Z06 cats that have apparently disintegrated.
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Old 02-03-2019, 07:55 PM
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Vibrant GESI UHO
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Old 02-07-2019, 12:47 PM
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If you disintegrated C6 Z06 Cats, you probably need to look at the tune, not the cat. You are almost certainly allowing them to get beyond a safe temperature (roughly 950* C) during either WOT or on transition to decel fuel cut. Both of these can be managed through the ECU calibration.
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Old 02-07-2019, 02:15 PM
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Originally Posted by TurboLX View Post
If you disintegrated C6 Z06 Cats, you probably need to look at the tune, not the cat. You are almost certainly allowing them to get beyond a safe temperature (roughly 950* C) during either WOT or on transition to decel fuel cut. Both of these can be managed through the ECU calibration.
Thanks. Andy's recalibrating the tune. The car never ran hotter than 185° though. The cats were used, so it's possible they'd been banged around and, from what I understand, once a piece breaks off, it cascades from there. I don't run the card hard either, so it was very weird that this happened. We're going to get the C6 Z06 cats made by Magnaflow. They're tougher, flow better and are CARB certified. So let's see.
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Old 02-08-2019, 04:35 AM
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Originally Posted by Turpid porpoise View Post
Vibrant GESI UHO
more info !
Can these withstand a rich afr ?
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Old 02-08-2019, 08:12 AM
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Originally Posted by LedfootLarry View Post
more info !
Can these withstand a rich afr ?
I'm not sure about the rich AFR but they are designed to flow 500-800HP through the 3" cat. I have one I'm getting ready to weld into my circuit Subaru.
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Old 02-08-2019, 02:03 PM
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I've had good luck with the metallic spun high flow cats from Magnaflow. I want to say they are 200 cell. This was in turbocharged 4 cylinders making less power, but 400-500hp thru a single cat. In theory should be similar heat/flow/conditions. Haven't used Vibrant, but every single one of the things I've used of their has been top notch.
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Old 02-09-2019, 06:59 AM
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The company who manufactures these for vibrant is Gesi , and its local to me, I emailed them yesterday wether they would stand up to a rich FI , here is there reply:
Thank you for the inquiry. Your interest in our product line is appreciated. In response to your email, a rich air fuel ratio will negatively affect any converter. It typically results in temperature fluctuations that could exceed the material’s capabilities. Our converters are definitely a more robust solution for the high performance market, they are capable of handling tremendous horsepower, but they do need to operate under the right settings. Our units will typically flow more than our competitors, and will keep check engine lights off… we just can’t guarantee their longevity in a rich fuel environment.
And I think they have a high cell count, like 300-400 cell.
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Old 02-09-2019, 12:24 PM
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Originally Posted by TurboLX View Post
If you disintegrated C6 Z06 Cats, you probably need to look at the tune, not the cat. You are almost certainly allowing them to get beyond a safe temperature (roughly 950* C) during either WOT or on transition to decel fuel cut. Both of these can be managed through the ECU calibration.
Thanks Greg!

As so often, Cat Overtemp is disabled in the tune, at least during tuning, and for a good reasons.

Anyway, since there is no temp sensor in the cat itself, I guess these values - and actions based on them - are because of some internal PCM calculation logic which is not visible in the tune.

So how to tune these?

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Old 02-09-2019, 12:29 PM
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Originally Posted by LedfootLarry View Post
"In response to your email, a rich air fuel ratio will negatively affect any converter. It typically results in temperature fluctuations that could exceed the material’s capabilities."...
Well, so rich afr affects catalysator negatively?

But isn't that exactly what Cat Overtemp protection is doing with C5 PCM stock tune...

Interesting indeed.
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Old 02-12-2019, 09:41 AM
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Originally Posted by Pekka_Perkeles View Post
Thanks Greg!

As so often, Cat Overtemp is disabled in the tune, at least during tuning, and for a good reasons.

Anyway, since there is no temp sensor in the cat itself, I guess these values - and actions based on them - are because of some internal PCM calculation logic which is not visible in the tune.

So how to tune these?

Yes, there is an exhaust temp (and catalyst temp) model within the ECU. It is roughly based on engine speed, total air/fuel flow, spark advance, and air-fuel ratio. You can often log the result of the factory calculation as "catalyst temp" in many scanners, but this is not necessarily accurate with modified engines.

When I do development programs with aftermarket companies, I like to install an actual thermocouple in the catalyst so I can log the temperature along with all the normal ECU data. I follow the same strategy in the aftermarket as I do in OEM applications when working to keep that temperature in a reliable range. YES, this means running rich at full load. The cat manufacturers are typically worried about rich operation at normal temps, not necessarily at full load. When you start making big power, with high flow rates and knock limited spark timing, you MUST run richer to control the cat temp or risk instantaneous failure. Their concern about "running rich" is usually skewed toward poisoning of the brick over time, which is a lower priority than avoiding an immediate meltdown (or burning the washcoat off) at high load/flow.
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Old 02-14-2019, 11:50 AM
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Originally Posted by TurboLX View Post
When I do development programs with aftermarket companies, I like to install an actual thermocouple in the catalyst so I can log the temperature along with all the normal ECU data. I follow the same strategy in the aftermarket as I do in OEM applications when working to keep that temperature in a reliable range. YES, this means running rich at full load.
Just out of curiosity, I checked some aftermarket tunes so that I could learn something. I compared those tunes with stock ones.

And here are the results:

- 2006 Z06 with Vortech kit vs. stock 2006 Z06: Max enrichment under cat overtemp protection changed from stock 1.21 to a 1.35
- 2007 LS2 vith Edelbrock E-force vs. stock 2006 LS2: no changes for cat overtemp protection
- 2011 Corvette Grand Sport with Vortech kit vs. stock Grand Sport: no changes for cat overtemp protection
- 2012 Camaro with Edelbrock E-force vs. stock LS3 Camaro: no changes for cat overtemp protection

Interesting indeed.
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Old Yesterday, 06:37 AM
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I've had some problems with the older stainless steel bullet cats

the work ok but durability just isn''t there and if you do a lot of racing and dyno work, take them off

they tend to blow out the centers with a reasonable tune

factory goes a bit rich (like 12.5 to 1) on na

if you lean er out for power expect to have troubles after a few years
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