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COT Enabled or Disabled

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Old 04-20-2009 | 11:16 AM
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Default COT Enabled or Disabled

I just got the car tuned last week and it is running great! I download the tune to my PC for backup and safe keeping (HP Tuners) and I compared it to the previous tune.

I noticed this time around he tunred off the Cat Over Temp, and I do have cats. Kooks headers with thier 3" cats/y-pipe.

Is this something I really want kept off all the time?
Old 04-20-2009 | 11:41 AM
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It's just another enrichment step at WOT.
Old 04-20-2009 | 11:51 AM
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Originally Posted by Frost
It's just another enrichment step at WOT.
yeah, but is this something I really want kept off all the time?
Old 04-20-2009 | 11:56 AM
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If u turn it off it is hard on the cats.
Old 04-20-2009 | 12:52 PM
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If you leave it on it can be hard on the HP too.
How do use the car that it would be hard on cats? Auto-X or road race?
Old 04-20-2009 | 02:14 PM
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You could play with the settings to reduce the
impact of it. 10.25:1 is probably stupid fat. With the
cats further back in the pipe you aren't going to
heat them as badly either. But GM had the research
to back their setup (probably bent by liability to
an absurdly conservative point) and we don't know
nuthin' from nuthin' about your max sustained EGT.

A metallic substrate cat is going to be more fragile
than a ceramic.

People burn out the Jet-Hot "Chore-Boy" cats
pretty easily. Which is why mine sit safely in a
box. Somewhere.

Now, unless your state mandates ***-to-mouth
or you loves da baby sealses, maybe you just
do not care a whole lot about the actual cat
performance and appearances are good enough.
Dunno about upstate New York, what you've got
to deal with.
Old 04-20-2009 | 02:52 PM
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Originally Posted by Frost
How do use the car that it would be hard on cats? Auto-X or road race?
It's mostly a daily drive. I rarely go WOT.


Originally Posted by jimmyblue
You could play with the settings to reduce the
impact of it. 10.25:1 is probably stupid fat. With the cats further back in the pipe you aren't going to heat them as badly either. But GM had the research
to back their setup (probably bent by liability to an absurdly conservative point) and we don't know nuthin' from nuthin' about your max sustained EGT.

A metallic substrate cat is going to be more fragile than a ceramic.

People burn out the Jet-Hot "Chore-Boy" cats pretty easily. Which is why mine sit safely in a box. Somewhere.

Now, unless your state mandates ***-to-mouth or you loves da baby sealses, maybe you just do not care a whole lot about the actual cat performance and appearances are good enough. Dunno about upstate New York, what you've got to deal with.
I didnt follow all of that, but I do care about my cats and want to keep things running as well as can be expected.
Old 04-20-2009 | 03:22 PM
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I would disable it unless you find physical evidence that your exhaust system is being subjected to extreme temps from the cat. I think you would know for sure that this is happening.
Old 04-21-2009 | 11:25 AM
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I disable COT on every car I've ever tuned. I haven't had a blown cat yet.

While we're on this subject. How does the PCM know to envoke COT? Do the o2 sensors provide an EGT feedback of sorts to the PCM off the heater circuit to estimate EGT perhaps? Thats really the only feesable way I could see it knowing.
Old 04-21-2009 | 12:09 PM
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Originally Posted by macca_779
I disable COT on every car I've ever tuned. I haven't had a blown cat yet.

While we're on this subject. How does the PCM know to envoke COT? Do the o2 sensors provide an EGT feedback of sorts to the PCM off the heater circuit to estimate EGT perhaps? Thats really the only feesable way I could see it knowing.
It is calculated. There is no way to directly measure it.
Old 04-21-2009 | 03:59 PM
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On some of the newer E38 processors (like in the trucks and SUVs), if you disable COT, the AFM will stop working and the converter will not lock up. Just adjust the fuel settings or raise the temp thresholds if it's a concern.
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Old 04-22-2009 | 05:38 AM
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It's disabled because it may kick in while tuining AFR.
Mine is disabled too, since years and the stock cats are still fine.
Old 04-22-2009 | 06:49 AM
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Originally Posted by tici
It's disabled because it may kick in while tuining AFR.
Mine is disabled too, since years and the stock cats are still fine.
I assumed he disabled it for tuning for that reason.

The only concern I have it beating up the cats.


Would re-enabling it now effect the AFR or the performance??
Old 04-22-2009 | 09:40 AM
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COT kicks in not too often, if it's a DD I guess you won't feel the difference.
If racing then maybe yes.
I disabled it also because with the SC I'm already rich (11.5) and I dont want to go 10:1 or so
Old 04-22-2009 | 10:14 AM
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Originally Posted by 2002_Z28_Six_Speed
It is calculated. There is no way to directly measure it.
Ok so how is it calculated?
Old 04-22-2009 | 10:26 AM
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I've seen scholarly SAE papers that go into fitting
the CAT temp prediction from RPM, (believed) AFR
and load and time. Of course AFR and load are two
things that are easily hoaxed when you start
modding, and upping performance means upping
RPM and load while leaning out AFR, so you push
yourself further into COT territory.

As to whether a 4th gen F-body's implementation
is so scholarly, or just a hack-job lookup, I couldn't
do more than guess.

One half-measure is to set your COT enrichment
table so simply equal your PE value; then even if
it kicks on, it will have no ill effect except MPG
while the cats are "cooling" (in its tiny little mind).
Old 04-23-2009 | 09:40 AM
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Thats not a bad Idea at all to keep COT at your richest PE. I might do that from now on instead of totally disabling it.



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