Looking to buy first Silverado and afm is making it hard

[SierraHD17]

6 minutes ago, aseibel said:

I don't know if that statement accurately assesses the value of AFM. Many of the people who disable it do so because they have either tuned, or lifted/leveled with larger tires and/or modified exhaust and probably drive a certain way. Let's hear from some people who disabled AFM on an otherwise stock truck and see if it made any difference for them. AFM is only useful for those who are fuel conscious. The bulk of people on this forum are more concerned with the look & sound of the truck. I would estimate that said group probably doesn't care or want the v4 mode anyway.

My own truck... 2015 6.2 double cab.  Sitting stock with the 1" block removed out of the back of the truck on stock rims and tires.  I turned off the afm and did nothing else tune wise with it.  The truck got the same economy average on a 65 mph on cruise highway trip as it did prior.  The system never activated at that speed in the first place unless coasting downhill in which case the deceleration fuel cutoff negates the afm anyway.  I'm not the only one.

[Mariachi09]

so what I'm hearing overall is at the newer trucks with AFM seem to be more reliable than the older models and as long as I change the oil frequently and do proper maintenance these newer models, specifically 207,2018 seem to be pretty reliable and I shouldn't have too much to worry about or deter me from considering this truck

[aseibel]

2 minutes ago, SierraHD17 said:

My own truck... 2015 6.2 double cab.  Sitting stock with the 1" block removed out of the back of the truck on stock rims and tires.  I turned off the afm and did nothing else tune wise with it.  The truck got the same economy average on a 65 mph on cruise highway trip as it did prior.  The system never activated at that speed in the first place unless coasting downhill in which case the deceleration fuel cutoff negates the afm anyway.  I'm not the only one.

Interesting. I find that mine activates while travelling 70 mpg on flat roads when not driving into the wind. This may only be 25% of the time, but I know that I would burn more fuel if I deactivated the system.

[SierraHD17]

3 minutes ago, aseibel said:

Interesting. I find that mine activates while travelling 70 mpg on flat roads when not driving into the wind. This may only be 25% of the time, but I know that I would burn more fuel if I deactivated the system.

Do you know though?  You haven't done anything to the truck and have never tried so stating that is just speculation.

[Grumpy Bear]

1 hour ago, SierraHD17 said:

I wouldn't buy a truck with active fuel management because I think the principle of killing the same 4 cylinders constantly is just plain stupid... and it is.  It just leads to ring coking from heat cycling along with the crappy lifter that falls apart.  Then again I would not buy one with a camshaft that slides back and forth in the block with some varying lobe arrangement like the new turbocharged 4 banger in the 2019s.  Making shit overly complicated in attempts to meet government mandates never makes anything better for the end user.  It's a roll of the dice... buy one and get 100000 trouble free miles or more or get a lemon that lives in the shop.  It's always been that way but what changes year to year is the odds.  Are anyone elses new trucks really any better though?  No, they aren't. 

 

I'm going to let you rethink than while you ponder the temperature it takes to 'coke' motor oil. Additional consideration might be given to the difference in temperatures between a running cylinder and one that is not. Especially at the ring interface. Hint, heat of combustion vs heat of compression. 

 

2 minutes ago, SierraHD17 said:

Do you know though?  You haven't done anything to the truck and have never tried so stating that is just speculation.

Don't know about Aseibel but yea, I know. Liner Logic Scan Gauge II and a data logger. Most higher trim levels also display V4-V8. That aside I've kept track of every gallon of fuel this truck has burned and under what conditions. My AFM is good for a statistical 8% improvement, day in day out. Then again I give it a fighting chance to work. 

[SierraHD17]

6 minutes ago, Grumpy Bear said:

 

I'm going to let you rethink than while you ponder the temperature it takes to 'coke' motor oil. Additional consideration might be given to the difference in temperatures between a running cylinder and one that is not. Especially at the ring interface. Hint, heat of combustion vs heat of compression. 

 

Don't know about Aseibel but yea, I know. Liner Logic Scan Gauge II and a data logger. Most higher trim levels also display V4-V8. That aside I've kept track of every gallon of fuel this truck has burned and under what conditions. My AFM is good for a statistical 8% improvement, day in day out. Then again I give it a fighting chance to work. 

I wont argue if it works for you at whatever speed you drive with a 6 cylinder truck but I question you this on the first part.  How many afm equipped engines have you ever torn down?  Any?  I have and it's not a coincidence how the 4 cylinders that cycle are full of enough carbon that the rings are stuck in the ring lands.  It's enough of an issue GM has tsbs out for the dealers for piston and ring replacement.  It is what it is.

[aseibel]

22 minutes ago, SierraHD17 said:

Do you know though?  You haven't done anything to the truck and have never tried so stating that is just speculation.

You are correct in saying that I cannot prove it. I can only estimate that during the 25% of my highway drive where only 4 cylinders are being used, I would burn more fuel if it was being dumped into all 8.

31 minutes ago, SierraHD17 said:

My own truck... The truck got the same economy average on a 65 mph on cruise highway trip as it did prior.  The system never activated at that speed in the first place unless coasting downhill in which case the deceleration fuel cutoff negates the afm anyway.

You stated that your truck never even entered V4 mode before you deactivated it. So how can you say it wouldn't have saved any fuel for you if the road conditions, weather conditions or loading conditions allowed it? All you are proving is that your typical drive apparently never benefited from AFM in the first place.

[SierraHD17]

5 minutes ago, aseibel said:

You are correct in saying that I cannot prove it. I can only estimate that during the 25% of my highway drive where only 4 cylinders are being used, I would burn more fuel if it was being dumped into all 8.

You stated that your truck never even entered V4 mode before you deactivated it. So how can you say it wouldn't have saved any fuel for you if the road conditions, weather conditions or loading conditions allowed it? All you are proving is that your typical drive apparently never benefited from AFM in the first place.

I guess so.  I have not seen an afm equipped truck above the 60 mph mark enter afm for more than a second without kicking out and I have been in a lot of them.  Unless of course there is a heavy tail wind or the road is downhill.  Slower speeds it works... higher is a mixed bag.  Is what it is.

[aseibel]

3 minutes ago, SierraHD17 said:

Slower speeds it works... higher is a mixed bag.  Is what it is.

That's exactly it. The wind drag increases exponentially with speed. One of my best MPG tanks I ever had was spent in cruise control at 60 mph. I was in v4 most of the time getting 25 mpg. When I'm going 70 it averages between 19-20. Maybe 22 max with favorable wind.

 

those people that always drive 75+ on the highway will never see the benefit of V4 mode because the truck is working too hard to push the air.

 

[SierraHD17]

4 minutes ago, aseibel said:

That's exactly it. The wind drag increases exponentially with speed. One of my best MPG tanks I ever had was spent in cruise control at 60 mph. I was in v4 most of the time getting 25 mpg. When I'm going 70 it averages between 19-20. Maybe 22 max with favorable wind.

 

those people that always drive 75+ on the highway will never see the benefit of V4 mode because the truck is working too hard to push the air.

 

Yeah I am not driving below the speed limit and never will.  Neither does the most of average drivers on the highway.  Slow it comes in.

[Brummie99]

I've had my Silverado 1500 LT for 6 months now and just passed the 8,000 mile mark. At first I found AFM to be a bit of a novelty but find it clunky. I can definitely feel when it kicks in or out although it's not too intrusive.

Most of the time I have the DIC on the economy display and try to drive with a light foot. My average over 8,000 miles is 20.7 mpg. My daily commute is about 50 miles round trip mostly at highway speeds on flat (Florida) roads. It regularly switches to V4 mode but never stays there for long. I keep an eye on the instant fuel economy and really don't see a significant improvement when it does switch to V4. I would think if it were only fuelling 4 pots instead of 8 there would be an immediate, noticeable change.

 

Today I have ordered the Range AFM disabler and will try it out for a month. If I don't notice any improvement, I'll send it back under their 30-day money-back guarantee.

[KARNUT]

I’m leery of the cylinder deactivation. Why? More moving parts associated. Better results with it, not much in my case. Before you really get to the long term results, their changing it. The biggest reasons 5.7 diesel we had three all junks. 8-6-4 Cadillac we had one. Get back to me when they start hitting 200K miles. That really wouldn’t matter their changing them again. I’ll pass on this one.


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[diyer2]

IMO

Every brand has it's issues.

What brand do you want to roll the dice on?

All vehicles are a crap shoot IMO, new or used.

Buy what pleases you.

 

 

 

[Jon A]

17 hours ago, Mariachi09 said:

Are the problems with afm severe enough to not  make it not worth getting a new Silverado? All the bad things I am reading are really pushing me away from buying one .

There's no reason to feel that way as the system can be easily disabled--even in a way that won't affect your warranty.

 

While it's obvious some here like the system, there's no denying the fact it is a liability.  The vast, vast, majority of major mechanical issues with these engines (hard parts breaking, valvetrains and sometimes entire engines needing to be replaced) reported here can be traced back to the AFM system.  No, it doesn't happen all that frequently, but the simple truth is those issues wouldn't have happened at all without it.

 

The good news is, the anecdotal evidence (doubtful anybody has done a long term, scientifically controlled study) is strong that simply disabling the system pretty much eliminates the possibility of these issues occurring.  And it makes sense from a mechanical standpoint, if you understand how the system works.

 

The most common mode of failure is the AFM lifters themselves getting stuck in the collapsed condition.  A pushrod engine with collapsed lifters will quickly destroy itself.  The AFM lifters use a small secondary spring to keep them riding on the cam lobe and to keep slack out of the valvetrain when in this condition.  The problem is they are way, way, too small to perform this function at anything other than low RPM.

 

So, when one or more gets stuck in the collapsed condition, anytime you accelerate even moderately (much less tow something up a hill) where the engine requires mid-range, much less high RPM, you are driving a pushrod engine with a collapsed lifter.  This will beat the valvetrain to death and possibly take the entire engine out with it if not identified and fixed immediately.  That doesn't even take into account all the secondary issues that occur when the computer is trying to fire that cylinder with one of the valves not working.

 

With the system disabled, the lifters are never "activated" to voluntarily collapse and lock themselves in that condition.  If they never enter that condition, it's much more difficult for them to get stuck in that condition.

 

Personally, I deactivated the system when my truck was nearly brand new for these reasons (I expect to keep it a long time, so long term durability is a goal).  Besides, most of my long trips are 75-85 MPH with a decent load and 34-35" tires so the potential benefit of the system was going to be minimal for me.  Would I feel even better physically removing these lifters and replacing them with dead-nuts reliable standard lifters (which would also allow the use of stronger valvesprings)?  Yes, and I plan to do that eventually.  That would give this engine the bulletproof valvetrain GM V8's used to be known for (and the current 6.0 in the HD's enjoys because it lacks this system).  But it's my belief that deactivating the system so dramatically reduces the chances of having an issue with it, there's not an urgent need to do that.  I'll get around to it when I eventually do a cam swap--and standard lifters allow the use of much improved cam lobes so you can have more power along with more durability.

 

[diyer2]

Well put Jon A.