Noticing an uptick in EGTs...ideas?

Hey all, noticing a trend that makes me curious. So I got a fancypants head unit a while back, that plugs into the OBD port and reads live engine data to display on programmable gauges. One of the readouts I like to have up is the EGT.

When I first got the unit, I'd rarely see temps over 1500F under heavier load or higher in the rev range. Usually hovered in the 1300s-low 1400s at highway speeds in 6th gear(manual), a little higher going uphill, etc.

Lately it's been hovering around 1500F under static(cruising) load, and I've occasionally seen it reach over 1650F under heavy acceleration or load.

Now, I'm not panicking just because I have a digital readout to look at. Just curious about how the system is set up, and what may cause this small-but-pronounced upward trend. I do know my spark plugs are probably a little overdue for replacement, so maybe some incomplete combustion blowing more burning fuel out the exhaust valves? it does seem a little down on power but it may be my imagination.

I don't know where the EGT sensor is located in the exhaust stream, before of after the cat, or if it's just coupled with the O2 sensor or something. Any enlightenment from someone who knows more about this system would be appreciated.

 

There are no tempterature sensors, catalyst temperature is calculated based on enginel load and amount of fuel being injected among other things.
@JustDSM can probably explain it a bit better as he deals with it in tuning.

 

@Dm93 is 100% spot on. There are no EGT sensors and the temperatures you're monitoring are the ECU reporting inferred data that was likely developed in a lab/modeling software to give the ECU the ability to compensate for EGT without having physical thermocouples in the exhaust which would probably fail at a higher rate. More reliable to gather the data and create mapping to have the ECU infer it versus continuously measure it. Anyhow..

These temperatures (there are 5 maps) that infer temperatures for different components in the exhaust. They are all RPM/Load based as mentioned and they are used to activate a secondary fuel map in the ECU to control/reduce catalyst temperatures (and associated components) to ensure long life.

Here's a pic of one of the maps:

 

Oh, really? That surprises me that it's just a calculated number. Then again I was also surprised to even see an EGT readout in a system that doesn't even read oil temp/pressure. So I guess it makes sense, sorta.

Wow, that's interesting. Makes more sense when you explain it that way. I learned something new today, thanks!
I appreciate your knowledge and work; one of these days I need to get with you about a tune. I've seen many of your threads, trying to find the hole to burn in my wallet to buy myself an HPTuner.

 

Let us know when that time comes! We have our own HPT Device now that is cheaper than a MPVI2/3.

 

Oooh, now it's even more tempting. And you sell the devices with prepackaged tunes for given configurations? My engine is bone stock, probably gonna keep it that way for the foreseeable future, but would really like to wake it up a bit and have some configurability. I've gotten used to the rev hang but it would be really nice to have better decel and engine braking.

 

i've noticed the same thing lately. i think they are doing something weird to the fuel. My catalytic converter temps went up a solid 300-400 degrees. usually would hover around 950-1050 degrees on highway and now it hovers around 1300-1450 degrees.

how hot can the cats get before they get damaged?

 

Absolutely! These will come with a base set of calibrations. Meaning you'll get the specific engine calibration, but it'll come with a variety of different throttle settings in full rev-hang delete and the more popular 50% rev-hang delete.

Of course we can adjust the throttle settings to your liking at no charge.

 

It's mainly programmed in as a form of protection for the catyletic converters.

i didn't notice any difference in engine braking but it does wake the truck up a bit in the mid throttle range and as a bounus my fuel mileage went up around 1mpg.


Wow, that's interesting. Makes more sense when you explain it that way. I learned something new today, thanks!
I appreciate your knowledge and work; one of these days I need to get with you about a tune. I've seen many of your threads, trying to find the hole to burn in my wallet to buy myself an HPTuner.[/QUOTE]

 

[/QUOTE]
i wonder if thicker oil in the rear diff would help with engine braking

 

You would likely lose more in MPGs than you would gain in engine braking.
V6 engines just don't give a whole lot of engine braking.