Yukon Denali 6.2 Entering PE When Towing at Cruise and Temps Climb Thoughts?

[ASX29]

Hello,

I have a 2010 Yukon XL Denali with the 6.2. It has always towed great with an open 18ft trailer and a Camaro getting around 12-13mpg on highway and temps were all normal. Recently I purchased a 20ft Enclosed trailer and the added wind resistance really makes everything struggle as far as mpg and heat. Weight is not a factor because pulling 8000lbs open trailer everything is ok. But with the drag on the enclosed trailer even empty I have to use manual mode to keep in 5th or 4th gear. In drive it will enter 6th gear then start to loose speed then downshift within 5-10 seconds. Which is understandable and not complaining about not using 6th gear. The biggest problem is the engine coolant temps. When in 5th and the road is flat its does OK at times but just rolling along I noticed it will enter into Open Loop/PE. Which its only commanding 14.0 at that specific area in the MAP but the temps climb and the MPG drops from 10-11mpg to 7mpg. Is this normal to be entering PE rolling down the highway at 60-65mph pulling a trailer? I have never really focused on that specific area of the fueling table before so it must be still factory parameters. I have read that richening a hot engine a little was supposed to cool the charge and bring temps down. Is that not the case? If its not supposed to enter PE that would be great because the 3-4 mpg I lose just trying to maintain speed really hurts the wallet when traveling 6-700 miles.

Also, I want to add that going up a hill is almost death to the entire drive train. Because dropping to 4th unlocks the converter and the trans temps spike to like 230* and the coolant temps go up to 240*. The odd thing is that I am not really leaning hard on it at all as there is still plenty of power on tap but if I try to accelerate up the hill I fear it might nuke itself. Are there any adjustment to be made by either pulling a little timing or adding more fuel to that specific area and try locking the converter in 4th to keep the temps down?

Here is a log of pulling the enclosed trailer empty enter:
5th gear empty trailer.hpl

[ASX29]

Here are the tune files for the ECM and TCM.
2010 GMC Yukon Denali XL (2.24.23)(NOAFM)(FLEXFUEL)(2018 VVT Angles & VE)(32.5dia)TUNED-4.hpt
2010 GMC Yukon Denali XL (TCM)(1mph Upshift Add_32.5 diameter)(275-60-20 Tires)(-20%TCCLockup)-3.hpt

[Alvin]

I have a 07 Denali XL and a few years back I went on a boys side by side trip with a bunch of nascar buddies. They all wanted to do 90mph up WV mountains and I couldn't keep up cause temp would climb on trans and engine. When I got back I put a new radiator in it and it totally solved that. After so many years the radiators just get blocked up by sand etc.

[ASX29]

I have a 07 Denali XL and a few years back I went on a boys side by side trip with a bunch of nascar buddies. They all wanted to do 90mph up WV mountains and I couldn't keep up cause temp would climb on trans and engine. When I got back I put a new radiator in it and it totally solved that. After so many years the radiators just get blocked up by sand etc.

Hey Alvin, thank you for that input. I have heard that as well about the radiator. Just swapping in a new radiator solved the overheating up hills?

[STAGEUP]

Might be time for a diesel or re-gearing. You cant have power, without more fuel. You're requesting more power than stoich can provide during towing. So naturally, the PCM is going to command more fuel in order to meet the power demand through your throttle input.

You can toy around with PE settings and TC settings, but ultimately, you will end up with marginal improvements.

You essentially added more weight, with the added drag. So you need to add a 40k trans cooler, and add more gearing to the differentials. Or get a diesel.

[blindsquirrel]

Are you saying that it's enabling PE, even on flat level ground, steady state? When throttle is less than the threshold (87%)?

edit: Only just looked at the log, yes that's what it's doing. At least according to the fuel system status flag. It might be helpful to add Catalyst Temp channels to your log, this looks kinda like something other than actual power enrich.

As a test you could change the PE EQ Ratio table and see if the commanded EQ changes to the new value, or stays the same. Something like a flat 1.17 for the whole table.

[blindsquirrel]

And... Virtual Flex is even less reliable than an AFM lifter. I don't know why anyone who has the means to turn that off, wouldn't.

[ASX29]

Might be time for a diesel or re-gearing. You cant have power, without more fuel. You're requesting more power than stoich can provide during towing. So naturally, the PCM is going to command more fuel in order to meet the power demand through your throttle input.

You can toy around with PE settings and TC settings, but ultimately, you will end up with marginal improvements.

You essentially added more weight, with the added drag. So you need to add a 40k trans cooler, and add more gearing to the differentials. Or get a diesel.

I totally agree that am literally on the threshold on that available power for stoich with the added drag. I really wanted a V-Nose trailer but had to settle on one without. Is there a way to add a little power and efficiency to that specific area when towing? Would removing a little VVT retard or adding a degree or 2 of timing raise the ceiling of available power and efficiency at cruising speeds?

[blindsquirrel]

screenshot.30-08-2023 10.08.59.png

[ASX29]

Are you saying that it's enabling PE, even on flat level ground, steady state? When throttle is less than the threshold (87%)?

edit: Only just looked at the log, yes that's what it's doing. At least according to the fuel system status flag. It might be helpful to add Catalyst Temp channels to your log, this looks kinda like something other than actual power enrich.

As a test you could change the PE EQ Ratio table and see if the commanded EQ changes to the new value, or stays the same. Something like a flat 1.17 for the whole table.

I am still poking through the tune to see where conditions are being met to enter OL/PE because I don't think its PE. I was leaning toward the CAT Overtemp because there really isnt much of a change or any change in throttle or map to enter PE.

Also, I agree with the Virtual Flex. I forgot I had it back on. It usually off. I think I had it on to see if it would pick up the 10% ethanol at our local gas station and it never did so yes, usually I have it off and tell my wife never to put e85 in it.

[blindsquirrel]

It shouldn't be enabling PE, unless it's both: MAP higher than 55 kPa, and; throttle more than 87%, at any RPM, since it's still the stock one-value-for-the-whole-table.

If you log the catalyst temps, you'll then have something to compare with the cat overtemp tables. I don't know for sure on these ECMs but I'll bet there a lot of other flags you could log that will show exactly what's active at any given time.

But as mentioned setting the PE table to some different value will tell you if it's not really PE. If you change it to 1.800 across the board, and it still goes to 1.045, then it's not PE.

edit another one: Yeah, nowhere in your PE table is there anything like '1.045'. This is not power enrich, it's something else that also just trips the 'OL' flag.

[SiriusC1024]

I have a 07 Denali XL and a few years back I went on a boys side by side trip with a bunch of nascar buddies. They all wanted to do 90mph up WV mountains and I couldn't keep up cause temp would climb on trans and engine. When I got back I put a new radiator in it and it totally solved that. After so many years the radiators just get blocked up by sand etc.

I use a product called Iron Out. Works amazingly well. You can get it at Walmart or wherever usually in the laundry aisle. It's the pure powder concentrate of Prestone Radiator Flush - oxalic acid and citric acid. Those chemicals are used to flush heat exchangers in industrial environments. Safe on all metals including soldered pipes. Flush the coolant system with water, add half a bottle then drive it for a couple days. After that flush again then refill with coolant/water mix.

[ASX29]

It shouldn't be enabling PE, unless it's both: MAP higher than 55 kPa, and; throttle more than 87%, at any RPM, since it's still the stock one-value-for-the-whole-table.

If you log the catalyst temps, you'll then have something to compare with the cat overtemp tables. I don't know for sure on these ECMs but I'll bet there a lot of other flags you could log that will show exactly what's active at any given time.

But as mentioned setting the PE table to some different value will tell you if it's not really PE. If you change it to 1.800 across the board, and it still goes to 1.045, then it's not PE.

edit another one: Yeah, nowhere in your PE table is there anything like '1.045'. This is not power enrich, it's something else that also just trips the 'OL' flag.

After looking at the Temp Thresholds for the "Catalyst Protection" I am pretty sure this is what it may be. I have an aftermarket Stereo and it allows me to view OBDII engine parameters that I keep on screen when I am towing because I can see the coolant temp to the degree rather than the dash gauge. One thing I have to log is EGT Temp. It must take the O2 temps I would guess. However, it hovers right around that 1,600-1,700 degree mark when towing. So I bet its that and it applying the EQ ratio offset based off the threshold.

EGT.jpg

[ASX29]

Thanks SiriusC1024! I will look into that as well.

[Alvin]

Hey Alvin, thank you for that input. I have heard that as well about the radiator. Just swapping in a new radiator solved the overheating up hills?

Yes it did. I think the fins were blocked by sand and dirt after so many years.