I've swapped a LS6 into my FD (third gen) Rx7 and am in the process of tuning it.
I saw to turn off COT while tuning. I have a magnaflow high flow cat with no kind of sensor on it for measuring temperature. I'm assuming that the cats usually have a sensor on them if they're measuring temperature?
If I'm correct, I assume I should just leave COT disabled on my tune permanently?
The cats do not have a temperature measuring device for COT to work. It is a calculated threshold programmed into the calibration (which is editable on some calibrations IIRC). What this does is increases the AFR of the commanded mixture to typically 11.7 (1.25). The extra fuel cools the cats and keeps them from boiling over in case of running lean (say 13.0 or leaner). If you have cats, you should command an AFR of at least (leanest) 12.8 to keep them alive. I would only command a leaner AFR after peak torque and no further then peak horsepower, and no leaner then 13.1. Good luck!
Interesting! Thanks for the info--I couldn't find anywhere that described the COT mechanism. I just assumed there was a heat sensor on the CAT itself.
I'm still not sure exactly what would trigger the COT protection mechanism (just out of curiosity)? Not in closed loop I would assume, or does it have a sort of timer mechanism that will richen the mixture briefly to cool down the cats?
Some people even say for a stock setup (un-ported heads and cam) there is nothing to be really had by going leaner than 12.8...You might get a 1hp or 2...Originally Posted by 12secSS
Here's an SAE paper on methods of calculating catalyst temp, I believe
this is the sort of scheme used by GM.
You would want to determine the best mixture -for your configuration-
straight up, and then figure how much you would sacrifice to keep a
set of functional catalytic converters.
I don't know if it's possible for Chris to add "calculated catalyst temp"
to the PIDs for scanning, that would be an interesting thing if not all
that useful in general.
The COT once it activates one time, seems to have a long "memory"
and a hair trigger.
If you just set the COT enrichment max to your PE values then it's not
going to meddle any, just (possibly) chew up the catalyst some. That
depends on how hard, how long, how lean. Which is a good reason not
to pass up a set of spares if you find them cheap.
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