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Strategies to keep cats from melting

WildHorse

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What would you suppose is the temp of the catalyst itself in the above scenarios?
That materials in the cat get superheated, so it wouldn't surprise me that when the exhaust exits the cats it would be hotter. Kind of like a blast furnace effect. When there's nothing impeding the flow, then the temps will get cooler the further down the exhaust port they get. Just a trolls (my) opinion.
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Grimreaper

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That's what 30 seconds or longer past the end if your pull? Seems a bit long to be unburned fuel build up but ive never seen temps pre/post redux before. Maybe it is buildup and residual heat.

Is there a similar hump during any other driving? From coasting to lite cruise maybe? Wonder if that's reactivation dumping a bit of fuel. Guessing it would require a timer to be in dfco for so long before needing to be relit.

Imagine jumping back on it in that range with no cot. I would not have thought the temps would behave like that though, at least not such a large delta. What's the gap after 30 seconds of steady state cruise?
 

engineermike

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During most driving, the downstream EGT runs between the upstream EGT and the inferred cat temp. Amplitude of downstream response to load and speed changes is rather muted, as if there is some significant thermal damping due to the catalyst. The only time the downstream EGT exceeds inferred temp is for the ~3 minutes after going WOT. After looking at several WOT pulls, the double hump isn't always there. It's not due to DFCO or cat re-light. The double hump happened immediately after cracking the throttle blade back open after coasting down.

The real mystery is...can the downstream temp be hotter than the cat temp? Is this even possible or is the inferred cat temp model that botched up? Heat is like pressure; it can only travel from the hotter component to the colder one. You can't heat gas to a temp hotter than the heater. The only way I can think of that makes this possible is if the flow velocity is very slow and we are seeing the effects of transport delay, where gas heats up to 1500 in the cat and slowly moves to the downstream EGT sensor while cooler incoming gas cools the cat. But, a quick calc seems to indicate the gas velocity in the cat is 5-10 ft/second. The phenomenon of higher downstream temp than cat temp is going on for up to 3 minutes after WOT, so I don't see that being the case.
 

WildHorse

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Bottom line: Don't assume factory cats will hold up to boost. Maybe the will, maybe they won't. If your worried about temps etc., get a quality set of aftermarket EPA legal cats as I mentioned a while ago.
 
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Torinate

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Honestly, from everything i've read the aftermarket cats don't hold up near as well as factory cats.

YMMV though...
 

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engineermike

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I actually trust oem cats more than aftermarket based on what I know.

The real issue here, IMO, is that no aftermarket supercharged tune has a cat temp model as good as stock. We also know that aftermarket tuners disable or delay cat protect because it will make more power and go faster. As PBD showed us on the gt500, it’s the easiest 40 hp you can gain. Roush runs their sc cars super rich in PE mode, which delays cot some, but Roush also underpredicts the cat temp and we see Roush cars fail cats relatively often. Whipple underpredicts cat temp and raises the cot threshold. With a limited data set, I’ve seen the stock gt500 go into cot after 2 seconds at wot but Whipple takes a full 6 seconds to enter cot. We know plenty of Whipple cars fail cats as well.

The sad truth is if you want cats to live in your supercharged coyote, it has to basically live in Cot mode nearly the whole time at wot, or you have to find some other creative way to cool them. I’m thinking about running lambda at around .72 in PE mode like Roush does, to delay Cot. You can offset some of the power loss by advancing the timing a little since richer will tolerate more spark.

The other option is to lower boost and advance timing further to also delay it. It’s going to be a bunch of trade-offs. Mine currently takes 5 seconds at wot to hit cot using a conservative cat temp model, and that’s running the wagon-wheel pulley and 21+ deg timing.

So, better to concentrate on delaying cot, or set up and tune the car to maximize power in cot since it’s inevitable anyway?
 

Ruiner46

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This might be outside the scope of this discussion a little bit, but I've been curious how E85 affects cat life with boost. Target lambda with E85 tends to be on the rich side compared to pump gas. Does ethanol cool cats better? Does it affect the reaction in the cat in a way that helps the cat temp?
 

engineermike

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@Ruiner46 the 2020 mustang gt stock tune has the inferred EGT tables populated for flex fuel. If you believe them, the EGT is very close between e85 and gasoline except at full load and 5000-6500 rpm+. At the point, they are saying e85 is 2-300 deg hotter EGT.
 

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LSchicago

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I'm interested to hear of Procharged experience on cat temps. My car seems to run very cool, even hot lapping at the strip. Has anyone melted the cats with a P1X?
 

Grimreaper

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I thought the cat was the heater. Breaking bonds requires energy.

If it's only after a wot pull then I'd lean towards unburned buildup due to decreased efficiency when running rich.

found this, still reading through it so not saying its the gospel. CCC is basically the setup we have, as close to the port as possible.

Exhaust gas temperatures were measured at the entrance of
CCC and UCC (Under-floor catalytic converter), and
catalyst temperatures were also measured at CCC and
UCC beds at 2500 rpm under various engine loads.
Results show that catalyst temperature is higher than
the exhaust gas temperature of catalyst inlet by
100~110°C. Hence, 950°C of catalyst inlet gas
temperature was considered as the threshold
temperature of catalyst damage, corresponding 1050°C
of catalyst temperature. The reason why the catalyst
temperature is higher than the catalyst inlet gas, is that
exothermic reactions take place in the catalyst when CO
gas is changed into CO2 gas.


https://www.researchgate.net/public...talytic_Converter_Temperature_in_an_SI_Engine
 

K4fxd

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Andy13186

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Before I put my SC on, I took my cats off. Added varex active mufflers to have quietish cold starts. no regrets.
 

markmurfie

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There you go. That is the best argument for removing the cats.

Co2 = bad........Right??? :sunglasses:
CO2 is bad for climate change... Allegedly, it's complicated.

CO is poisonous and much worst for us, better for the atmosphere tho, in regards to the green house effect.

LMAO

I'm still thinking about how to approach this temperature data. Seems useful to correct the O2 sensor heater duty cycle model.
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