Is disabling COT and turbo overtemp safe?

[Spcbrn]

Hi,

I'm in the process of tuning my WOT fuel by using the power enrichment on a 1.4T engine with a E78 ECM.
I was thinking about disabling both catalyst and turbo overtemp protection once I'm happy with my WOT lambda but is it safe to do so?

My logic is that if I can get power enrichment tuned properly to ensure my engine won't run too lean at WOT, COT and turbo overtemp features aren't needed anymore. I also noticed that on these engines, the catalyst and turbo temperatures weren't monitored with a sensor but calculated by the ECM...

It just seems like a kinda clumsy way to ensure the catalyst won't melt by dumping a ton of fuel, what are your thoughts on this?

[SiriusC1024]

Hot exhaust also means hot pistons and valves. Up to you whether you want to reduce the life of your components.

[tunerpro]

Hi,

I'm in the process of tuning my WOT fuel by using the power enrichment on a 1.4T engine with a E78 ECM.
I was thinking about disabling both catalyst and turbo overtemp protection once I'm happy with my WOT lambda but is it safe to do so?

My logic is that if I can get power enrichment tuned properly to ensure my engine won't run too lean at WOT, COT and turbo overtemp features aren't needed anymore. I also noticed that on these engines, the catalyst and turbo temperatures weren't monitored with a sensor but calculated by the ECM...

It just seems like a kinda clumsy way to ensure the catalyst won't melt by dumping a ton of fuel, what are your thoughts on this?

GM didn't put those features in there just to waste more fuel, they serve a specific purpose, and that's to control the temperature of critical powertrain and emission controls. The fact people have unconstrained control over disabling these features is probably the same reason GM decided not to let us into their systems anymore.

Personally I don't second-guess GM's army of engineers and their decision making behind stuff like this without hard data. In this case, I'd be looking at profiling observed turbo and catalyst temperatures on the stock calibration and then studying the effects of modifying these features.

[sbarisic]

GM didn't put those features in there just to waste more fuel, they serve a specific purpose, and that's to control the temperature of critical powertrain and emission controls. The fact people have unconstrained control over disabling these features is probably the same reason GM decided not to let us into their systems anymore.

Personally I don't second-guess GM's army of engineers and their decision making behind stuff like this without hard data. In this case, I'd be looking at profiling observed turbo and catalyst temperatures on the stock calibration and then studying the effects of modifying these features.

They put it there because it's cheap. If it was perfect, there wouldn't be different engine calibrations for same engine+ecu combo every year.


Had another toy recently, another turbo engine with the E80 ECU and about 30'000 miles on the clock. Can't even keep the commanded boost within 0.1 bar on everything stock (Desired MAP vs actual on images below). Brand new car.
The wastegate DC table looks like somebody smashed the keyboard with a hammer and then left it like that. Oh and the default boost control PID setup likes to overshoot and oscillate whenever it feels like it.

a.png

b.png

Hi,

I'm in the process of tuning my WOT fuel by using the power enrichment on a 1.4T engine with a E78 ECM.
I was thinking about disabling both catalyst and turbo overtemp protection once I'm happy with my WOT lambda but is it safe to do so?

My logic is that if I can get power enrichment tuned properly to ensure my engine won't run too lean at WOT, COT and turbo overtemp features aren't needed anymore. I also noticed that on these engines, the catalyst and turbo temperatures weren't monitored with a sensor but calculated by the ECM...

It just seems like a kinda clumsy way to ensure the catalyst won't melt by dumping a ton of fuel, what are your thoughts on this?

It depends, what is your actual measured lambda? On my car specifically in stock form, the actual is off on the rich side by about 10% (in lambda, not AFR units). Sounds low, but it's the difference between 12 AFR commanded and 10.8 AFR received.
Wide open throttle reached numbers below 11 on the stock calibration often.


I have both on mine disabled, but i don't have a catalytic converter anymore.

In stock form, power enrichment isn't enabled, and instead it relies on the "turbocharger overtemp protection" to enrich the fuel mixture. That means on wide open throttle, the commanded and actual AFR are going to be about 14.7 while under boost for a certain amount of time.

(This log is from when the car was stock except for torque limiters increased)

c.png

After that, it starts enriching up to a certain number that's set in the Turbocharger Protection tab based on some internal temperature model which isn't measured, it's just guessed numbers. And that can be as low as 10.0 AFR. Enriching CAN happen for a certain amount of time after you let go of the throttle which is pointless.

The "Hot Engine" part is where you can add some "cool down" fuel enrichment if you're worried, and allows for a little bit leaner PE values. It adds fuel based on the oil temp, mine never rises above 105-106 deg C anyway.

While we're at that, i recommend putting 95C instead of default 105C in the "System - Fans - Desired ECT" table. It controls the electronic thermostat to open sooner and keeps the engine quite a bit cooler when under high load.
Log both engine oil temp and engine coolant temp, oil temp under high turbo usage can spike up to 10 degrees C hotter than coolant temp.

My PE is set up like this

LPsnvlqDrf.png

The engine likes fuel somewhere between 11.5 and 12. Watch out for knock retard.
I'm running a bigger turbo that doesn't even spool below 3000 RPM with stock internals.

And check under the hood JUST AFTER some spirited driving, glow like this is normal and expected. It's the best way to gauge the temperature of exhaust gasses if you don't have an EGT sensor .

20220731_214209.jpg

[tunerpro]

They put it there because it's cheap. If it was perfect, there wouldn't be different engine calibrations for same engine+ecu combo every year.


Had another toy recently, another turbo engine with the E80 ECU and about 30'000 miles on the clock. Can't even keep the commanded boost within 0.1 bar on everything stock (Desired MAP vs actual on images below). Brand new car.
The wastegate DC table looks like somebody smashed the keyboard with a hammer and then left it like that. Oh and the default boost control PID setup likes to overshoot and oscillate whenever it feels like it.

Idk, seems like it's "perfect enough", especially since they have to warranty emissions parts like catalytic converters for something like 100,000 miles. Catalyst temp protection, and turbo temp protection are all elements of the overall thermal management of the engine. Even if you think you're smarter than the guys that designed this stuff because you have a laptop and tuning software, can read fancy labels, have determined you no longer need "catalyst temp protection" because you don't have a catalytic converter anymore, and have subsequently disabled the feature, you can be assured that you're altering the thermal model of all of the engine components, not just the catalytic converter. Without thorough analysis (and measuring how red your turbo is after you do a pull on the car isn't good enough) you can't be sure what the side effects are.

[eXo3901]

You can raise the temp thresholds and it should become a non-issue. I said raise, not max.

As mentioned, knowing the model under stock conditions will help you understand the model when modifications are introduced. This will aid in determining how far to raise the temp thresholds. Not perfect science, but most of us do not have commented code or engineering documents to reference when we adjust oddball settings.

[sbarisic]

Keeping these systems on defeats the purpose of enabling power enrichment as they will override it and dump more fuel than needed anyway.

And running max load all the time with a properly set up power enrichment won't allow the turbo or cat to overheat in the first place.

There's also the third option of having both PE and temperature protections enabled, but with lowered enrichment numbers.
The default enrichment values are ridiculous.



Besides, go out and test it for yourself, but the model doesn't care if you're dumping 10 AFR all the time or 14.7 AFR all the time, the calculated exhaust temp values will be the same under the same driving conditions and stretch of the road. They only vary by load and torque.

[SiriusC1024]

Service life will be reduced if overtemp protection is modified. There's no arguing it. Up to the individual if that's acceptable.

[PSYKOSTEVO]

If you are catless, turning off COT is an acceptable idea. If you still have a cat, then you need it still to maintain proper cooling so that you don't melt the element in the catalytic converter. Turbo Overtemp is best left ON, but use your own judgement on how high you feel comfortable raising the threshold.

[Spcbrn]

Thank you all for your replies and taking the time to explain your opinions on this.
I prefer staying on the safe side of things so I'll leave these settings stock and see if it ever gets in my way which I doubt, I've never seen COT/Turbocharger protection turned on during a log session.

[sbarisic]

I've never seen COT/Turbocharger protection turned on during a log session.

You mean the on/off flag in the log? That's never on in my logs either, you know it's on because it automatically increases fuel, like this (this is a stock car log).
The maximum fuel varies depending on the predicted temperature setpoints and max/min EQ ratio.

5FlwwlOlVa.png

This can be dangerous, if you disable turbocharger protection and cat protection and don't enable power enrichment or set it up incorrectly so it doesn't actually enable, the car will always run at lambda 1 under boost and you'll melt a hole in the piston.

[Spcbrn]

You mean the on/off flag in the log? That's never on in my logs either, you know it's on because it automatically increases fuel, like this (this is a stock car log).

Hm... I was indeed relying on the on/off flags but I guess it's not working/showing on VCM Scanner.
Oh by the way, unrelated but I know you're tuning an Opel just like me. Have you ever noticed the intake/exhaust cam angles were misrepresented in the logs or is it just me?

I do have PE turned on and it's setting up properly although it still needs some work to get it where I want exactly.

[sbarisic]

Have you ever noticed the intake/exhaust cam angles were misrepresented in the logs or is it just me?

Misrepresented how? I know there's some tune files where angles in VCM Editor show 0 to 8 degrees for WOT angles. But the correct values are 0 to 32. Mine show up properly in the log and in the tune.

[Spcbrn]

Sorry, that was a bad choice of word from me! I noticed in some conditions that the logged angle didn't follow the desired angle but the logged angle is correct in the sense of it's the actual cam position!

For example, when idling I will have my intake parking at 24? and the exhaust at 10? but in my tune it's commanding 15? for intake and 12? for exhaust.
From what I've seen there a no multipliers or other tables that might explain this. The only tables commanding the cam angles when not in WOT are the high baro table 33103 and 33106.