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05 CTS V 07 ESCALADE
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Discussion Starter #1
Rumor has it that the Hi Flo cats that have low cell counts (200-300) can cause the exhaust to emit smoke when they heat up. I've had a few folks tell me that on track days the see some light colored smoke coming out the back at high rpms. Usually later in the day. We've never been able to find the cause. No head gasket or oil issues present. I've had this issue before and after engine mods. The only common denominator is the exhaust system (Corsa with Hi-Flo cats). Anyone experience this?
 

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05 CTS V 07 ESCALADE
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Discussion Starter #3
I have a catch can. I was also thinking oil slosh on high Gs. I've pulled 1.2 several times.
 

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2016 ATS Premium 6-spd MT
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I would assume its the crankcase vent thats pumping oil back through the intake. At high rpm, oil pressure dramatically increases, meaning more will be pushed through the intake and will be burned in the exhaust.
I have a catch can. I was also thinking oil slosh on high Gs. I've pulled 1.2 several times.
Both very plausible causes I would think.

The only thing else I could think of would be a storage and release phenomenon whereby the catalyst stores up and releases gases on its substrate matrix due to the high level of gases coming through.

Well ... it sounds good, anyway.
 

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Discussion Starter #5
For real Randy? That sounds to good to be made up.
 

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2016 ATS Premium 6-spd MT
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13,966 Posts
For real Randy? That sounds to good to be made up.
Back when I used to work as an engineer in exhaust emissions controls, we used to talk about this phenomenon with respect to oxygen on the catalyst's surface and its ability to combine with excess hydrocarbons and carbon monoxide emitted from the combustion cylinders during A/F dithering (cyclical variations designed into the TB fuel injection system).

I have absolutely no idea if this same phenomenon is at work in what you observed, however.
 
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