LNF Cat overtemp Lambda

[Iam Broke]

Did a long pull speed run tonight and saw the cat temp exceed 1700 degrees, COT Lambda is around .71 and that's where she went on the charts after I nls into 4th.

What is a safe cat temp? It was still pulling good, but .71 is pig rich on this thing. I was seeing 3* KR so I backed it out of the WOT timing for now but just wondering which way to go here.

I can change the COT Lambda table to the same as the Power enrich one, just don't want to melt the cat. It's a ZZP DP with a 3" magnaflow cat on it.

Advise?? Opinions?

[oldskool]

I'm also curious about this. The cat temp is not a a measured parameter, it is a calcualted/estimated one. It behaves more like a timer - the longer you're at WOT, the higher it goes. So I guess autocrossers must melt cats all the time.

How have more conventional t/c cars delt with cat temperature if at all? DSMs/evos? WRX/STIs? supra? 300zx? 1.8t? I'm not aware that any of these models come with an EGT sensor, or that they dump fuel based on a calculated parameter. But I could be wrong.

In my opinion, if the base PE AFR melts the cat, there is a problem. My PE lambda is ~0.87 with meth injection, and my richest cell in the COT table is ~0.82. 0.71 lambda is a joke.

[Iam Broke]

See, I was thinking it was a temperature from the o2 sensor after the cat. In instrumentation, we use platinum TC's to measure in that range. If it's a guesstimate, that really blows.

[justmike]

If I am not mistaken the Caralyst temp is taken by a sensor and I have the "Catalyst Temp B1S1 (SAE) selected in my scanner config and I get actual temps.

[shabby]

Unless the wideband or the rear o2 sensor measures this there is no actual sensor, its simply a formula just like the oil temp "sensor".

[Iam Broke]

If I am not mistaken the Caralyst temp is taken by a sensor and I have the "Catalyst Temp B1S1 (SAE) selected in my scanner config and I get actual temps.

That is the temp I am speaking of during long hard pulls, it maxes out over 1700*f and my Lambda goes to .71 from the COT protection.

We need to know if it's actual temp and what the safe limit is. Any GM engineers here?
I hate to run that rich to keep things relatively cooler. I don't see how adding more fuel cools it off. If the cat sees more unburnt fuel, wouldn't it generate more heat as it burns it off?

[justmike]

Unless the wideband or the rear o2 sensor measures this there is no actual sensor, its simply a formula just like the oil temp "sensor".

Now you have me wondering .. looks like there is also a "Catalyst Temp B2S1 (SAE)" as well. I wonder if Steve P would know?

[Terminator2]

That is the temp I am speaking of during long hard pulls, it maxes out over 1700*f and my Lambda goes to .71 from the COT protection.

We need to know if it's actual temp and what the safe limit is. Any GM engineers here?
I hate to run that rich to keep things relatively cooler. I don't see how adding more fuel cools it off. If the cat sees more unburnt fuel, wouldn't it generate more heat as it burns it off?

Just set the cells that normally command 0.72 lambda to 0.86 or whatever your richest PE lambda values are.

[Iam Broke]

Just set the cells that normally command 0.72 lambda to 0.86 or whatever your richest PE lambda values are.

Done. Thank you, I'll see how that works out.

I still can't exceed 14 degrees advance at WOT, high loads, without seeing KR kick in even at a .87 PE Lambda.

[justmike]

So I got what I consider the definitive answer from someone I trust on the Cat temp ...

I do not recall seeing a temp sensor, so my guess is that it is a fairly decent formula. There is no listing for any temp sensor for the cat in the service information, and the HO2S 1&2 (Heated O2 Sensor) show no signal for temperature output, only the inputs to heat the sensor, and the hi/lo signals out.

[Oh Lordy]

Done. Thank you, I'll see how that works out.

I still can't exceed 14 degrees advance at WOT, high loads, without seeing KR kick in even at a .87 PE Lambda.

I've tried everything for my timing and can't exceed 11 degrees near WOT with .85 or .86 PE Lambda. I guess it's the heat. Averaging 95* with lots of humidity around here.

[justmike]

Have you replaced the stock intercooler?

[Iam Broke]

I've tried everything for my timing and can't exceed 11 degrees near WOT with .85 or .86 PE Lambda. I guess it's the heat. Averaging 95* with lots of humidity around here.

When I was commanding .86 PE lambda, actual under load was .85. I now command .87 and get the .86 I want. I've tried it richer and leaner by a few points with no change on my KR at WOT. I'll blame it on the oxygenated 93 octane in the area I live until I can beat this.

[Chris@HPTuners]

there is no sensor, the cat temp is an estimate calculated by the ECM. There are a lot of calibrations used to estimate the temperature eg. airflow, fuel, spark advance, vehicle speed etc.

obviously in the OEM envirnment they use a real sensor to ensure the estimated temp is close to the measured in all driving situations.

for a regular ceramic subsrate cat the maximum temp is around 900-950 degC before you start reducing its service life, at about 1200C the whole core of the cat becomes a nice molten blob. metal substrate cats can go a little above 1000C but not much.

generally short high temperature conditions are not too damaging (such as a pass on the drag strip), but sustained high temps cat kill a cat quite quickly eg. road racing lap after lap at high RPM with COT disabled.

[Oh Lordy]

Have you replaced the stock intercooler?

I have a stock 09 and have not. When I do get my KR, it's on a clean pass with IAT2 temps of 98 to 108max. I try to duplicate the same freshly warmed up vehicle to 190, cruise do to the interstate and log in 3rd gear.

[Iam Broke]

there is no sensor, the cat temp is an estimate calculated by the ECM. There are a lot of calibrations used to estimate the temperature eg. airflow, fuel, spark advance, vehicle speed etc.

obviously in the OEM envirnment they use a real sensor to ensure the estimated temp is close to the measured in all driving situations.

for a regular ceramic subsrate cat the maximum temp is around 900-950 degC before you start reducing its service life, at about 1200C the whole core of the cat becomes a nice molten blob. metal substrate cats can go a little above 1000C but not much.

generally short high temperature conditions are not too damaging (such as a pass on the drag strip), but sustained high temps cat kill a cat quite quickly eg. road racing lap after lap at high RPM with COT disabled.

I hit 1750*f at WOT in long runs on the indicated cat temp, that's 954*C.

I can't find what the Magnaflow 3" cat ZZP uses on the DP is composed of. I'll assume ceramic, so I guess I'll toast it if I keep it up.

Anyone want a catted DP?

[Terminator2]

I've tried everything for my timing and can't exceed 11 degrees near WOT with .85 or .86 PE Lambda. I guess it's the heat. Averaging 95* with lots of humidity around here.

17* and no KR here.

[Oh Lordy]

17* and no KR here.

I'm thinking it's not all because of the timing. Weather being relatively similar day to day this week, I'll get KR sometimes at that load/rpm and then other times not I check Ambient Temps, IAT, & IAT2 and they are similar to previous logs. I dunno.

[oldskool]

.

for a regular ceramic subsrate cat the maximum temp is around 900-950 degC before you start reducing its service life, at about 1200C the whole core of the cat becomes a nice molten blob. metal substrate cats can go a little above 1000C but not much.

Holy shit! So I'm guessing if the calculated value is even within 25% of actual, these cats are not going to last long at all. It is very easy to see temps hit above 1700*F (~925*C).

Is this a common occurance across different platforms?

[Terminator2]

Holy shit! So I'm guessing if the calculated value is even within 25% of actual, these cats are not going to last long at all. It is very easy to see temps hit above 1700*F (~925*C).

Is this a common occurance across different platforms?

If no one has melted a cat yet it means that the calculated value is probably higher than the actual value.