BREAKING: GM is officially recalling the L87

[blanchard7684]

In the lugging regime where many perils exist (high loading, pinging), lets say 1500~2000 RPM, the 6.2L isn't particularly any torque monster by usual big block standards nor is it that much of a delta over 5.3L... especially not if its not running on all cylinders.. I have plotted the torque curves below. Its just that the smart guys who thought DFM was even worth releasing didn't realize it is really BAD to be lugging and also be not operating on all cylinders. (Random guess - Some high up in the R&D team had this cool idea so it made it out..)

View attachment 455882

Along with what @jfoj has indicated with shifting programming unloading the 5.3 to a greater degree, I've also seen that the DFM system on 5.3 in my 24 Suburban doesn't spend much time engaged and when it does it is only going to 7 or 6 cylinders. Any slight incline or wind and it downshifts and knocks it out of DFM. It takes very little applied load to disengage DFM.

So imagine that load on fewer and fewer cylinders...

Here is a plot I made from a freeway run. I engage and disengage DFM via L10/L9. L9 rpm is about 1800 rpm and l10 rpm is about 1660 rpm. This is with cruise on. You can see some small hills the throttle opens alot. this is a good reference for load. From experience I can see that if the 5.3 is at a sustained throttle percentage of 55% for greater than a few seconds it comands a downshift. So these small hills were on verge of a downshift.

You can see the moderate hill got a downshift and hit 2300 rpm (L8). Also a huge spike in throttle. I've run the same route with a decent headwind and hit L7 (2600+ RPM).

The hills I'm talking about I don't have an inclinometer reference but they are laughably small probably to what most would consider a hill.

Similar plot I've seen from a 6.2 in similar vehicle look remarkably different. Downshifting is minimal to non existent which infers a high load at low rpm. If i'm not mistaken I recall repeated instances of 100% load with no downshifting in rpm ranges at or below 1600 rpm.

Essentially what I've learned is that although the 5.3 is a heavily laden engine in a huge vehicle like the Suburban, the load seems to be "better managed" than the 6.2.

Thus the 5.3 can "get away" with running a 0w20.

(also note how many instances of a sub 14.7 afr is being recorded at constant speed of 78 mph)

 

[Vladimir2306]

The 5.3l is not put under the stress the 6.2l is by the TCM causing very high Torque loading up to 100% at 1500-1700 when cruising on the highway pulling slight to medium grades. I have not towed with my truck yet or put the vehicle in Tow mode and monitored the Torque loading yet, but I assume in Tow mode the TCM will use more engine RPM overall, i.e. downshift more frequently and into lower gears to use RPM to its advantage.

You are mistaken, the 5.3 is under even greater load than the 6.2 because it has less volume and power, thereby working with greater efficiency than the 6.2

 

[Vladimir2306]

Along with what @jfoj has indicated with shifting programming unloading the 5.3 to a greater degree, I've also seen that the DFM system on 5.3 in my 24 Suburban doesn't spend much time engaged and when it does it is only going to 7 or 6 cylinders. Any slight incline or wind and it downshifts and knocks it out of DFM. It takes very little applied load to disengage DFM.

So imagine that load on fewer and fewer cylinders...

Here is a plot I made from a freeway run. I engage and disengage DFM via L10/L9. L9 rpm is about 1800 rpm and l10 rpm is about 1660 rpm. This is with cruise on. You can see some small hills the throttle opens alot. this is a good reference for load. From experience I can see that if the 5.3 is at a sustained throttle percentage of 55% for greater than a few seconds it comands a downshift. So these small hills were on verge of a downshift.

You can see the moderate hill got a downshift and hit 2300 rpm (L8). Also a huge spike in throttle. I've run the same route with a decent headwind and hit L7 (2600+ RPM).

The hills I'm talking about I don't have an inclinometer reference but they are laughably small probably to what most would consider a hill.

View attachment 455924

Similar plot I've seen from a 6.2 in similar vehicle look remarkably different. Downshifting is minimal to non existent which infers a high load at low rpm. If i'm not mistaken I recall repeated instances of 100% load with no downshifting in rpm ranges at or below 1600 rpm.

Essentially what I've learned is that although the 5.3 is a heavily laden engine in a huge vehicle like the Suburban, the load seems to be "better managed" than the 6.2.

Thus the 5.3 can "get away" with running a 0w20.

(also note how many instances of a sub 14.7 afr is being recorded at constant speed of 78 mph)

The 6.2 engine also rarely rides the L10 on the highway, or rather, it goes at 60-70 mph. But as soon as there is a slope or headwind, the automatic transmission switches to 9th gear, or even 8th

 

[22BlackDenali]

Mine is on the list. Got the notice in the app.

Has anyone taken his truck in for this “inspection” yet? (I’m assuming it’s too soon after the notice.) Looking forward to hearing what transpired.

I called for an appointment yesterday, my dealer said they are not ready to start executing this inspection/recall because they still don't have clarity from GM of what the steps are if inspection fails.

 

[blanchard7684]

The 6.2 engine also rarely rides the L10 on the highway, or rather, it goes at 60-70 mph. But as soon as there is a slope or headwind, the automatic transmission switches to 9th gear, or even 8th

...And the data logging I have is starting from L9.

 

[Slstorch]

I am literally sitting in my 2022 Tahoe with my flashers on at a stoplight and a failed engine. I just was googling about this and found that the truck was recalled two days ago. The tow truck is on its way. I sure hope GM is going to replace this engine for free!

 

[KMeloney]

I am literally sitting in my 2022 Tahoe with my flashers on at a stoplight and a failed engine. I just was googling about this and found that the truck was recalled two days ago. The tow truck is on its way. I sure hope GM is going to replace this engine for free!

Do you know for sure that it’s the engine and not the fuel unit? (Either way, sorry man!)

 

[Slstorch]

Do you know for sure

Do you know for sure that it’s the engine and not the fuel unit? (Either way, sorry man!)

that it’s the engine and not the fuel unit? (Either way, sorry man!)

Do you know for sure that it’s the engine and not the fuel unit? (Either way, sorry man!)

It won’t even crank with a jumper on it. It died on a slow decel. Tried to crank it and it cranked real slow and then froze. So my next question is, for people that had to replace the engine out of warranty. Is GM going to pay them back?

 

[Slstorch]

Do you know for sure

Do you know for sure that it’s the engine and not the fuel unit? (Either way, sorry man!)

that it’s the engine and not the fuel unit? (Either way, sorry man!)

Do you know for sure that it’s the engine and not the fuel unit? (Either way, sorry man!)

It won’t even crank with a jumper on it. It died on a slow decel. Tried to crank it and it cranked real slow and then froze. So my next question is, for people that had to replace the engine out of warranty. Is GM going to pay them back?

Do you know for sure that it’s the engine and not the fuel unit? (Either way, sorry man!)

 

[viven44]

@blanchard7684 really good info, thanks!

@Slstorch what a timing, so sorry you have to put up with this BS from GM