Catalyst Temperature PID Values (1 Viewer)

[TheGrrrrr]

I'd be interested to get a sense of what range of values folks are seeing on their Catalyst temperature (Bank 1 Sensor 1) PID under normal or various driving conditions. Most resources online say 500f to 800f under normal conditions and up to 1200f under heavy load. I can find no indication as to how relevant those numbers are to our 5.7L V8 engine vehicles, but I am interested in getting even an anecdotal baseline from folks who use OBD Fusion or the like. I'll be adding those PIDs to my logging for the trip to LCDC this weekend for compares.

This afternoon at 5pm in 113f ambient temps I drove for about 30 - 45 minutes alternating between surface streets and freeways running 40mph and 75mph respectively. Under higher RPM loads accelerating up to 75mph I saw over 1400f with sustained temps in the high 1200f to 1350f dropping quick to 1000f when load was reduced. Very small sample size but has me wondering. No CEL or codes.

 

[TLC2013]

I’ll add this to my dashboard and will report my numbers. Won’t be for a few days but I’ll log these catalyst temps to compare.
I have seen my fuel boil at high elevations, around 7,500ft and 90+F temps. Never enough to trigger any lights but was smelling fuel and have seen the residue on the fuel door and rear quarter panel.

My LC has full BB skids, and Dissent Bumpers, weighs between 7,000-7,500 lbs fully loaded.

 

[bloc]

I’d be careful comparing our data to online recommendations until we see evidence that things are actually failing.

 

[TheGrrrrr]

I’d be careful comparing our data to online recommendations until we see evidence that things are actually failing.

Precisely why I'm trying to capture some data points from our community.

 

[bloc]

Precisely why I'm trying to capture some data points from our community.

I guess what I’m asking is if we aren’t seeing failures, why worry about the temps?

 

[TheGrrrrr]

I guess what I’m asking is if we aren’t seeing failures, why worry about the temps?

I'm not sure we aren't seeing failures. We get fuel boiling and purge inefficiencies without throwing codes all the time. Seems possible that the Cats could be failing and generating extra heat contributing to these issues without throwing a code as well. Failure isn't binary. If the VSV is operating at 30% but hasn't stopped working completely, I would consider that a failure despite it not triggering a code.

If everyone is seeing catalyst temps in that 1300f to 1400f then I can quickly rule out that a failing or partially clogged Cat is contributing to the issue.

 

[bloc]

I'm not sure we aren't seeing failures. We get fuel boiling and purge inefficiencies without throwing codes all the time. Seems possible that the Cats could be failing and generating extra heat contributing to these issues without throwing a code as well. Failure isn't binary. If the VSV is operating at 30% but hasn't stopped working completely, I would consider that a failure despite it not triggering a code.

If everyone is seeing catalyst temps in that 1300f to 1400f then I can quickly rule out that a failing or partially clogged Cat is contributing to the issue.

The whole point of the secondary oxygen sensors is to monitor catalyst effectiveness and let the computer know if they aren't working correctly. This is a more direct measurement than what the vehicle is doing with the evap system, and pretty much top of the list of things that will throw a code.

Additionally I believe different types of failures allow a certain number of start/stop cycles before they'll throw a code, which means if subsequent drive cycles don't have the fail condition the light may not get triggered. A failed cat shouldn't ever really fix itself..

Still, I'm curious what others come up with on these numbers. Keep in mind that the vehicle can't directly measure cat temperature, it is calculating it based on other metrics and assumptions.

 

[TheGrrrrr]

The whole point of the secondary oxygen sensors is to monitor catalyst effectiveness and let the computer know if they aren't working correctly. This is a more direct measurement than what the vehicle is doing with the evap system, and pretty much top of the list of things that will throw a code.

Good point.

Additionally I believe different types of failures allow a certain number of start/stop cycles before they'll throw a code, which means if subsequent drive cycles don't have the fail condition the light may not get triggered. A failed cat shouldn't ever really fix itself..

My thinking isn't that its fixed itself, but that it hasn't failed badly enough to trigger a code, but has failed badly enough to contribute to the vapor build-up. or more specifically to rule it out.

Still, I'm curious what others come up with on these numbers.

Thats all I'm after in this thread.

 

[bloc]

My thinking isn't that its fixed itself, but that it hasn't failed badly enough to trigger a code, but has failed badly enough to contribute to the vapor build-up. or more specifically to rule it out.

Is the suspicion that failed catalysts are increasing the underbody and therefore fuel temps?

 

[TheGrrrrr]

Is the suspicion that failed catalysts are increasing the underbody and therefore fuel temps?

Given the proximity to the fuel lines, yes I want to rule out the notion that a cat operating at 200 - 300 degrees above normal could be a contributing factor if thats the case.