Strategies to keep cats from melting

[MKL_DS]

I never got a chance to measure the size of the Redeye cats, but, here’s some interesting info...
At least as of 2021 MY, the 392 and Hellcat and Redeye/SS models all use the same cats.

I’m told it’s not a solid brick, more like 2 fat pancakes with a gap between them.

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[Torinate]

Interesting. In a way similar to the mustang with 2 bricks and a space between them where the O2 sensor is.

 

[jrsimon27]

Remove them and get a fouler.

 

[Torinate]

Remove them and get a fouler.

Yes, that’s the easy way. But I’m looking for ways to keep them and have them work without failing. I see you’re outside the US, where are you located?

 

[ahl395]

I’ve been wondering about a water meth injection kit and if it would reduce the cylinder temperature as well. At least enough to reduce the cat temp and maybe keep it under the temp threshold.

It's been awhile, but if I remember correctly according to the calculated cat temp PID, meth dropped my EGT by about 200 degrees

 

[Torinate]

It's been awhile, but if I remember correctly according to the calculated cat temp PID, meth dropped my EGT by about 200 degrees

Wow! Thanks for that!

200* is huge when you’re teetering on the edge lol.

That’s a big difference. Would likely drop the cat temps back into a normal range.

 

[ahl395]

Wow! Thanks for that!

200* is huge when you’re teetering on the edge lol.

That’s a big difference. Would likely drop the cat temps back into a normal range.

I've heard mixed things on if the reading is accurate, but the consistent drop shows that it helps IMO and meth is known to drop EGTs drastically. If your running boost on a stock motor with tight rings, that EGT drop will help prevent a ringland delete from overheating them too.

Also that was small boost (around 12psi) on a small shot of meth (around 12GPH). On bigger setups I'd bet there'd be even more improvement.

 

[Torinate]

Anything to help the safety margin. Lol

 

[engineermike]

More information for the thread. I did 2 more pulls yesterday. Cat protect kicked in 5-6 seconds into the pull on both. Two interesting things happened. 1) On the first pull cat temp control came in at 1680 deg f. Cat temp peaked at 1690 then started falling and was below 1680 by the time I let off. 2) Both time when exhaust temp control kicked it it actually cut throttle some. I think this is part of the exhaust temp control strategy but I can’t find much on it in the calibration.

 

[engineermike]

Another thing, I found this posted to eng-tips. If correct, it shows “only” a 2.5% power loss when dropping from peak power lambda down to 0.71 lambda, but an exhaust temp reduction of 180 deg f. This matches the earlier paper I posted.

.08 = .89 lambda
.09 = .79 lambda
.10 = .71 lambda
.11 = .64 lambda

 

[Torinate]

That’s really interesting. I wonder if the guys with the Roush (and Roush tuning) that experience a fall off on the back half in the 1/4 are experiencing this exact thing. With cat temps climbing and protection coming on closing the throttle some.

Makes me wonder...

 

[Torinate]

Another thing, I found this posted to eng-tips. If correct, it shows “only” a 2.5% power loss when dropping from peak power lambda down to 0.71 lambda, but an exhaust temp reduction of 180 deg f.

.08 = .89 lambda
.09 = .79 lambda
.10 = .71 lambda
.11 = .64 lambda

That’s a big drop in cat temps. 2.5% is a good trade off if you asked me to save the cats and motor.

 

[engineermike]

That’s really interesting. I wonder if the guys with the Roush (and Roush tuning) that experience a fall off on the back half in the 1/4 are experiencing this exact thing. With cat temps climbing and protection coming on closing the throttle some.

Makes me wonder...

I’m pretty sure the roush throttle closing issue was actually an LSPI load limit as a function of manifold charge temp.

 

[J17GT]

More information for the thread. I did 2 more pulls yesterday. Cat protect kicked in 5-6 seconds into the pull on both. Two interesting things happened. 1) On the first pull cat temp control came in at 1680 deg f. Cat temp peaked at 1690 then started falling and was below 1680 by the time I let off. 2) Both time when exhaust temp control kicked it it actually cut throttle some. I think this is part of the exhaust temp control strategy but I can’t find much on it in the calibration.

Nice to see that the cat temp leveled out and did not continue to climb. How long would you say the pull was?

 

[engineermike]

Nice to see that the cat temp leveled out and did not continue to climb. How long would you say the pull was?

6.6 seconds.

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