Unsure if I want Tahoe with AFM

[wsteele]

I think your plan is solid and understand the motivation/initiative thing.

As for the reman crate, I went through GM as I had the work done at a GMC dealer. The motor took a crap on my wife and I was out of town and the dealership was only a block away so I asked them to take a look. First time I used them but they are stand up guys and have had them work on my SUV's anytime I need a dealer do something.

I have always been one of those that assumed the dealer service department was an overpriced training ground for techs, at the customer expense. When we moved to Idaho, I didn't know any good shops and needed a few minor things taken care of, so tried the local GM dealer. Wow, what a difference. They are pretty darn competent, very honest (more than once they have told me I didn't need what I thought I needed, with a pennies on the dollar fix.). Their prices are always competitive (I can't change my own oil/filter for less than they charge and they cheerfully throw in a front to back rotation when I ask).

I am pretty sure I can do quite a bit better using one of the highly rated shops I have found around me, with one of the other reman suppliers, versus using my GM dealer (the other shops are a lot closer as well), but if the situation calls for me to use the dealer (like the truck is already there), I wouldn't hesitate to use them and a genuine GM engine. I know the GM engine would be more, but I would bet all the money in my pocket, the labor would be a wash and the quality of workmanship, just as good or better.

PS - As an indication of my lack of initiative, I have that front end 1.5" leveling hardware in the garage, have the dimension all worked out for the position sensor link and I just can't face that cold garage floor.

 

[wjburken]

I have always been one of those that assumed the dealer service department was an overpriced training ground for techs, at the customer expense. When we moved to Idaho, I didn't know any good shops and needed a few minor things taken care of, so tried the local GM dealer. Wow, what a difference. They are pretty darn competent, very honest (more than once they have told me I didn't need what I thought I needed, with a pennies on the dollar fix.). Their prices are always competitive (I can't change my own oil/filter for less than they charge and they cheerfully throw in a front to back rotation when I ask).

I am pretty sure I can do quite a bit better using one of the highly rated shops I have found around me, with one of the other reman suppliers, versus using my GM dealer (the other shops are a lot closer as well), but if the situation calls for me to use the dealer (like the truck is already there), I wouldn't hesitate to use them and a genuine GM engine. I know the GM engine would be more, but I would bet all the money in my pocket, the labor would be a wash and the quality of workmanship, just as good or better.

Understand completely.

This particular dealer is 20 miles away, but is in the town my wife works in. They are very upfront with me. I have had about 50/50 luck with dealerships.

I liked the fact that the GM crate came with a nationwide GM warranty for parts and labor for 100K. It was nice knowing that if I had a problem anywhere, I could take it to any GM dealer in the country and have it covered.

 

[Larryjb]

When I looked at all the engine/transmission changes throughout the years along with the efficiency numbers, the biggest changes seemed to come from, in order of most effective to least:
1) 4 speed to 6 speed to 10 speed transmissions
2) direct injection
3) DOD

My impressions is that DOD moderately helps when driving at highway speeds under 60 mph on flat land with no wind. Any moderate hills, acceleration to pass, winds, loads will require more power. It will be interesting to see if AFM is a significant improvement (GM's Active Fuel Management which allows finer control over cylinder deactivation).

Remember that hard acceleration enriches the fuel mixture which is really bad for fuel economy. With a transmission able to choose gear ratios better matched to the engine, the engine can operate staying closer to its ideal fuel mixture.

 

[gooffeyguy]

When I looked at all the engine/transmission changes throughout the years along with the efficiency numbers, the biggest changes seemed to come from, in order of most effective to least:
1) 4 speed to 6 speed to 10 speed transmissions
2) direct injection
3) DOD

My impressions is that DOD moderately helps when driving at highway speeds under 60 mph on flat land with no wind. Any moderate hills, acceleration to pass, winds, loads will require more power. It will be interesting to see if AFM is a significant improvement (GM's Active Fuel Management which allows finer control over cylinder deactivation).

Remember that hard acceleration enriches the fuel mixture which is really bad for fuel economy. With a transmission able to choose gear ratios better matched to the engine, the engine can operate staying closer to its ideal fuel mixture.

Where does VVT fall on this list?


On another note, do these engines have roller lifters?

Sent from my SM-G930V using Tapatalk

 

[iamdub]

When I looked at all the engine/transmission changes throughout the years along with the efficiency numbers, the biggest changes seemed to come from, in order of most effective to least:
1) 4 speed to 6 speed to 10 speed transmissions
2) direct injection
3) DOD

My impressions is that DOD moderately helps when driving at highway speeds under 60 mph on flat land with no wind. Any moderate hills, acceleration to pass, winds, loads will require more power. It will be interesting to see if AFM is a significant improvement (GM's Active Fuel Management which allows finer control over cylinder deactivation).

Remember that hard acceleration enriches the fuel mixture which is really bad for fuel economy. With a transmission able to choose gear ratios better matched to the engine, the engine can operate staying closer to its ideal fuel mixture.

AFM is DOD. Displacement on demand was the term coined decades ago for the "8-6-4" Cadillac in '81. Active Fuel Management is just the modern day proper name for the displacement on demand system. Due to the flop the Caddy engine was, I don't blame them for NOT keeping the DOD term for the newer iteration. There is no difference in operation between the system introduced in the 2007 year models through the 2018 year models. There have been improvement to the components, though, starting in 2010 or 2011. 2019 brought Dynamic Fuel Management, which is the progression of AFM. It has 17 different cylinder modes that can engage or disengage any of all eight cylinders as needed rather than just manipulate four exclusive cylinders.

Your impression is correct. For most real-world driving instances outside of GM's closed testing course(s), AFM is rarely engaged so its minute benefits are far outweighed by the cost of repairing it. With my mods, I'm getting the same or better MPG as I did babying it with AFM.

 

[iamdub]

Where does VVT fall on this list?


On another note, do these engines have roller lifters?

Sent from my SM-G930V using Tapatalk

VVT is great. Rarely a failure and when there is, it's usually a failed cam phaser that can be replaced or deleted (locked out) without the major surgery an AFM delete entails.

Yes, they have roller lifters.

 

[wjburken]

AFM is DOD. Displacement on demand was the term coined decades ago for the "8-6-4" Cadillac in '81. Active Fuel Management is just the modern day proper name for the displacement on demand system. Due to the flop the Caddy engine was, I don't blame them for NOT keeping the DOD term for the newer iteration. There is no difference in operation between the system introduced in the 2007 year models through the 2018 year models. There have been improvement to the components, though, starting in 2010 or 2011. 2019 brought Dynamic Fuel Management, which is the progression of AFM. It has 17 different cylinder modes that can engage or disengage any of all eight cylinders as needed rather than just manipulate four exclusive cylinders.

Your impression is correct. For most real-world driving instances outside of GM's closed testing course(s), AFM is rarely engaged so its minute benefits are far outweighed by the cost of repairing it. With my mods, I'm getting the same or better MPG as I did babying it with AFM.

 

[iamdub]

View attachment 268286

Hey, I tried to give AFM its fair due! I quickly determined that it didn't have any.

 

[wjburken]

Hey, I tried to give AFM its fair due! I quickly determined that it didn't have any.

Oh - Not knocking what you said. Not at all. Just trying to give you some props man. I am not a big fan of AFM either, just haven't gotten to the point that I want to dig into it on our 2013 yet. That whole DOD crap back in the day was a joke as well, for sure.

 

[donjetman]

A neighbor had their 2012 XL Denali 2wd parked out in their front yard with a for sale sign this week, $13k. I stopped and looked at it. 178K miles. Beautiful inside and out. But I kept thinking about the AFM problems and the fact we need AWD.

It sold quickly.