Catemp PID- looking for info

[engineermike]

Thanks! Interesting that it came on at 1680. Was this noticeable driving or you saw lambda drop? What is cot lambda on your setup?
Did you see this in the log where it “dropped”?

The 1680 is specified in the tune.

Since I am commanding .75 at wot and 7500 rpm, the cot lambda isn’t dramatically different. The only way I know is that the fuel source changes to “exhaust temperature control”.

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[sjmurphy34]

Just an FYI, those aren't real cat temps. There's no temperature sensor in the exhaust. The temperatures you're seeing are inferred temps based on lots of factors (air flow, engine speed, load, lambda, etc.). They're usually fairly close though assuming everything is stock. The stock cal is set to be safe to protect the cats, and for most cats in recent cars, sustained temps above 950C is generally dangerous cutoff temp where sustained temps above that can melt substrates and damage the cats.

You are correct that generally temperature protection kicks in around 1650-1700F or so. You'll also notice that if you go above a certain pedal percent (usually around 90%) you'll get enrichment before temps get above the thresholds.

So if you're modifying your tune or adding boost or other things, I'm not so sure I would trust the inferred cat temps. I think most tuners generally just play on the safe side though and go a little bit more rich during high speed/high load conditions.

 

[Torinate]

I guess I’ll have to figure a way to log with the nGauge to see where COT comes in and look for a source for exhaust temp control. I can also run a log for kissy lamda and see where the changes occur. Would there be any reason for a tuner to turn this off? I’m tuned with Lund and to be honest, never knew to even ask this. I could send an email and ask, but with everything happening I’d rather not at this point.

I hear what you’re saying as far as to the accuracy of the PID without a temp sensor. However, inferred may be just as accurate or accurate enough to make a difference. 950c is about 1740f. The word sustained though throws a wrench to me. What or how long is “sustained”? If we look at 1/4 mile pass, if @engineermike is getting into cot at the 5 second mark that would mean he would be in cot for another 4-5 seconds +/- to the end of the run. Is that sustained? I’ve went 10.4 so assuming the same 5 seconds, I’m in it longer at 5-6 seconds all things being equal. I’ve never looked at the catemp after or at the end of a run so not sure what it maxed out at. Good thing I’ve only been to the track a couple times on rental days lol.

I need to make a custom log to monitor catemp, fuel source, lamda, SAFTOT and KnockR to see where things are at. Anything I need to log with this as well?

 

[sjmurphy34]

Sorry I guess sustained isn't really an accurate term. Its really tough to say how long a cat will survive during an overtemp. If it just briefly overtemps and then cools quickly back down its less likely it will have damage than if you go 1000+degC for a longer period. Generally the calibration attempts to be safe and overestimate the temps a bit up at the upper temp limits for protection as well. So the chances you're going to overtemp them when stock isn't very high. And assuming your tuner doesn't really mess up something you're probably safe too.

Assuming you're at WOP for the whole quarter mile you're going to get power enrichment as soon as you go WOP and then as the model senses the temps are getting up near the calibrated limits, it will start enriching more and you'll go into a cat protection lambda until it thinks the temperatures have dropped or it reaches it's enrichment limit. Again this is all on a stock non boosted car, not entirely sure how its handled aftermarket tune wise.

Assuming you are overtemping your cats, you won't always fully melt them first go. But you probably are wearing away the coatings in your bricks which lessens the ability for your cats to be able to store oxygen, which in turn makes them pollute a little more and could eventually set P0420/P0430 codes.

 

[brianbr]

I did a 3rd gear pull, 19 Ededbrock stage 1. By the end of the pull at 7400 cat temp was 1706 then continued up to 1760 during decel before starting to cool

 

[engineermike]

Got another log later yesterday. It went into cot 6.5 seconds into the pull when cat temp exceeded 1680, just as programmed. Temp peaked at 1694 at 8 seconds in when I let out. Lambda was .76 before cot and .71 after.

 

[Torinate]

I did a 3rd gear pull, 19 Ededbrock stage 1. By the end of the pull at 7400 cat temp was 1706 then continued up to 1760 during decel before starting to cool

Who’s tune do you have?

 

[Torinate]

Got another log later yesterday. It went into cot 6.5 seconds into the pull when cat temp exceeded 1680, just as programmed. Temp peaked at 1694 at 8 seconds in when I let out. Lambda was .76 before cot and .71 after.

Consistent with the previous log. Does the temp stop building as soon as you let out out or continue up as BrianBr’s did?

 

[J17GT]

Consistent with the previous log. Does the temp stop building as soon as you let out out or continue up as BrianBr’s did?

That is my question too. I have a Whipple stage 2 with their supplied tune going on my car this week. I have full stock exhaust with no plans to change it. Does the temp peak or does it continue to climb?

I do hit a few drag race events a year and plan to have my foot buried to the floor for 11 seconds. If I'm lucky, 10.9x.

Whipple says cat protection will hit in 4 seconds or so. Sounds like that is right on the money with the info here.

 

[brianbr]

Who’s tune do you have?

Its the Edelbrock tune

 

[engineermike]

Does the temp stop building as soon as you let out out or continue up as BrianBr’s did?

Mine starts dropping immediately when I let out, though the drop is slower than I would have thought.

Whipple says cat protection will hit in 4 seconds or so. Sounds like that is right on the money with the info here.

Whipple runs the lambda closer to max power, which also results in less spark advance. This results in more power, but also I would expect it to hit COT sooner. My take based on the limited amount of data posted here, is that by richening my lamda up top, I've delayed COT by 2-3 seconds.

 

[J17GT]

So the question is, when in COT does the temp peak and plateau during a pull or at some point is COT unable to overcome the heat and it continues to climb?

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