Strategies to keep cats from melting

[engineermike]

I’m not sure I trust a metallic foil substrate converter to work better than the oem-style ceramic honeycomb.

Sponsored

 

[Walt Kowalski]

I can’t stand cats. Remove them.
.
.
.
.
or at least keep them inside your home.

 

[shogun32]

and run an L shaped MIL on your secondary o2.

which is just another way to spell 'cheat'. What makes you think the EPA won't come after those as emissions defeat devices?

 

[J17GT]

basically the same thing as i mentioned above.. Buy those, punch them out, and run an L shaped MIL on your secondary o2. Have your tuner turn your OM monitors back on. the end.

The thing is I want to run cats.....I don't want the noise and especially the smell.

 

[Rothgray]

which is just another way to spell 'cheat'. What makes you think the EPA won't come after those as emissions defeat devices?

I have no guarantees they won't in the future, but today it is a viable option.

 

[Rothgray]

The thing is I want to run cats.....I don't want the noise and especially the smell.

Run E85 ;)

 

[Gregory347]

I’m considering going with the gesi g-sport cats... I had a conversation with tech support at gesi. He said the key to cats not failing is proper tuning and cot not dumping too much fuel.. cats are murdered they usually never commit suicide is what he said... with that I was told by my tuner that cot is either on or off... so does the ecu calculate lambda during cot based on o2 sensor feedback or is it a fixed value?

 

[engineermike]

I don’t think I understand the question.
It looks to me like it’s triggered on when the exhaust temp exceeds the max threshold, typically 1650 deg f. You can specify the minimum lambda. I can’t tell if it goes straight to the minimum lambda or if it uses a feedback control to target an exhaust temp.

There are other components that also limit exhaust temp (flange, o2 sensor) and other minimum lambdas (combustion stability) as well.

 

[Torinate]

How do I know if COT is on or off? Any way to tell?

 

[engineermike]

How do I know if COT is on or off? Any way to tell?

In HPScanner it’s the fuel source pid. If you don’t have HPScanner then the tell-tale is when your lambda suddenly nosedives to the 0.7 range.

 

[Torinate]

Shoot. Using nGauge with Lund tune.

 

[MKL_DS]

How do I know if COT is on or off? Any way to tell?

Ask your tuner.
Also the in dash AFR gauge should show it as well. Likely drops to the low 11s/high 10s in COT.

 

[engineermike]

I log with HPScanner. They are called O2 Voltage B1S2 and B2S2. The voltage doesn't matter as much as the switching. With new cats the voltage drifts very slowly over time. With aged cats, the voltage will toggle high to low (I think 0.450v is the mid-point) back and forth slowly, like 5-30 second swings. With failed cats, the voltage will swing very rapidly. The pic below shows a new cat (gray) and an aged but still functioning cat (white). The timespan is 30 seconds.

To complete this thought, here is a snipping of what a bad cat looks like. It was bad enough to set a code:

So the top graph gray line is a new cat. Top graph white line is a marginal cat that won't trigger a code. Bottom graph gray line is a bad cat that will set a code. The smoother the better.

 

[Gregory347]

You can specify the minimum lambda. I can’t tell if it goes straight to the minimum lambda or if it uses a feedback control to target an exhaust temp.

Thanks for your response and for being generous with your knowledge. This is what I was looking for. Does it go to a set value that you can determine or control to target an exhaust temp. Also would the Gesi cats need a different lamda for this purpose than would factory cats to make max power and protect the cats from overtemp. Sorry if my questions are a bit convoluted, these concepts/strategies are fairly new to me.

 

[engineermike]

I’m not super knowledgeable in the area, but I believe the gesi cats use a 316 foil coated with catalyst. At first glance, you see that 316 has a melting point of over 2500 deg f so they shouldn’t melt. However, significant degradation of properties occurs well before 2500. I believe the stock cats use a ceramic substrate, which is easily good for another 1000 deg over 316.

In the cases of broken ceramics, I wonder if the damage is done more by thermal shock than absolute temperature. In other words, were the cats heated up faster than the stainless shell, which caused the ceramic to over stress and crack.

Sponsored