Forced induction and melted cats....
04-15-2012, 11:17 PM
#21
Drifting
Does Cat Over Temp protection in the tune prevent melting? I have had my cats in for 4 years now with my twin turbo setup and don't think I have a problem. I watch my EGT's closely and all seems fine. You guys are scaring me...
04-15-2012, 11:32 PM
#22
Safety Car
04-17-2012, 11:22 AM
#26
Le Mans Master
There is an on going discussion about failed cats on supercharged cars here including some input from the industry.
http://www.camaro5.com/forums/showthread.php?t=183230
http://www.camaro5.com/forums/showthread.php?t=183230
04-18-2012, 09:04 AM
#27
Do you guys realize this is exactly why Catalyst Overtemp Protection fueling exist? Under high load (and temps), the only viable solution in most cases is to add a significant amount of fuel for cooling. It's not just intake charge cooling. The richer mixture lowers the bulk flame temp, which in turn reduces exhaust gas temperatures and catalyst mid-bed temperatures. This is why you see guys making more power with a leaner mixture on the factory ZR1 and CTS-V, but the factory guys knew what it takes to keep catalysts alive for over 100k miles on a 600hp engine. They're not dumping fuel just to be conservative or to sandbag the numbers, it's REQUIRED to keep things alive for the intended life of the car.
Another point is that when you actually add all that "extra" fuel for exhaust cooling, it slows down the laminar flame speed so you actually NEED to advance the ignition timing in order to make sure everything burns in the cylinders instead of in the exhaust on the way out. A "conservative tune" with lower timing can actually be VERY BAD for catalyst temps. You'll notice that the factory tune has a table that adds timing as the commanded mixture gets richer. A lot of inexperienced tuners flatline this table and then wonder why they burned cats or O2 sensors out of the car. Hrmmm...
Another point is that when you actually add all that "extra" fuel for exhaust cooling, it slows down the laminar flame speed so you actually NEED to advance the ignition timing in order to make sure everything burns in the cylinders instead of in the exhaust on the way out. A "conservative tune" with lower timing can actually be VERY BAD for catalyst temps. You'll notice that the factory tune has a table that adds timing as the commanded mixture gets richer. A lot of inexperienced tuners flatline this table and then wonder why they burned cats or O2 sensors out of the car. Hrmmm...
04-18-2012, 10:22 AM
#28
Former Vendor
Makes me wonder how much power I was down at the Trona event. I wasn't having the kind of 2nd gear traction problems I usually do.
On the drive home I was noticing a weird exhaust resonating sound at certain rpm/load. Now I know it was the cats.
Think I'll lose much power switching to ZR1 manifolds and cats?
On the drive home I was noticing a weird exhaust resonating sound at certain rpm/load. Now I know it was the cats.
Think I'll lose much power switching to ZR1 manifolds and cats?
04-18-2012, 11:44 AM
#29
Drifting
Do you guys realize this is exactly why Catalyst Overtemp Protection fueling exist? Under high load (and temps), the only viable solution in most cases is to add a significant amount of fuel for cooling. It's not just intake charge cooling. The richer mixture lowers the bulk flame temp, which in turn reduces exhaust gas temperatures and catalyst mid-bed temperatures. This is why you see guys making more power with a leaner mixture on the factory ZR1 and CTS-V, but the factory guys knew what it takes to keep catalysts alive for over 100k miles on a 600hp engine. They're not dumping fuel just to be conservative or to sandbag the numbers, it's REQUIRED to keep things alive for the intended life of the car.
Another point is that when you actually add all that "extra" fuel for exhaust cooling, it slows down the laminar flame speed so you actually NEED to advance the ignition timing in order to make sure everything burns in the cylinders instead of in the exhaust on the way out. A "conservative tune" with lower timing can actually be VERY BAD for catalyst temps. You'll notice that the factory tune has a table that adds timing as the commanded mixture gets richer. A lot of inexperienced tuners flatline this table and then wonder why they burned cats or O2 sensors out of the car. Hrmmm...
Another point is that when you actually add all that "extra" fuel for exhaust cooling, it slows down the laminar flame speed so you actually NEED to advance the ignition timing in order to make sure everything burns in the cylinders instead of in the exhaust on the way out. A "conservative tune" with lower timing can actually be VERY BAD for catalyst temps. You'll notice that the factory tune has a table that adds timing as the commanded mixture gets richer. A lot of inexperienced tuners flatline this table and then wonder why they burned cats or O2 sensors out of the car. Hrmmm...
My EGT's never reach the point where they should melt my cats.
04-18-2012, 01:19 PM
#30
Instructor
Member Since: Feb 2012
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Are we back @ "THE TUNE"???? Shut off the GM Engineering "Safe Guards" contained within "THE TUNE", because you don't understand them or think that they are not necessary. You get what you get and YES I FREAKING TOLD YOU SO!!!!!!!!!!
04-19-2012, 02:23 AM
#35
Le Mans Master
Member Since: Jan 2003
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Here is a picture of a Random Technology high flow cat that came apart and wedged itself inside a custom made X pipe. This car was a 383 LT4 in a C4 Corvette that I built a few years ago, it made 620 to the wheels with a Vortec T trim as a power adder. It to was running a fancy methanol injection system.
And yes there was a HUGE loss of power when this happened.
And yes there was a HUGE loss of power when this happened.
04-19-2012, 02:26 AM
#36
Le Mans Master
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I had a LPE car in my shop a few months ago with a E Force system on top of a LS3 GS. With their GT9 cam and the blower it made nearly 600 to the ground. On my dyno it made within 5hp of their dyno which is also a Mustang, they had 595 on their dyno sheet and I had 590, all this through stock LS3 manifolds and CATs.
04-19-2012, 10:08 AM
#37
Former Vendor
I had a LPE car in my shop a few months ago with a E Force system on top of a LS3 GS. With their GT9 cam and the blower it made nearly 600 to the ground. On my dyno it made within 5hp of their dyno which is also a Mustang, they had 595 on their dyno sheet and I had 590, all this through stock LS3 manifolds and CATs.
04-19-2012, 10:44 AM
#38
Drifting
It only kicks in when your temperature gets hot enough to damage the cats. You still need to fix the root cause of the high temps...probably a symptom of an overly lean condition. To me this is only a safety setting similar to your IAT timing table which pulls timing when IAT is high to prevent knock.
04-19-2012, 11:54 AM
#39
Team Owner
04-20-2012, 10:08 AM
#40
Melting Slicks
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I think a lot of it really has to do with how hard you drive the car. Right before I found the cats had melted, I had made a bunch of hard pulls deep into 5th gear. I'd say that's what finished them off.
