Cylinder Deactivation Issues?

Nanotech Environmental · July 23, 2017

Thats right, the only time it was In V4 mode for any length was down hill when your coasting. At 72 MPH it wasn't on much, just enough to mess up the good exhaust sound.

I'd suggest that maybe yours isn't working correctly, as it should run in V4 on flat ground & slight inclines at 72 mph and of course all downhills & it should show improved fuel economy intantaneously as soon as it switches to V4. The only exception being if you're driving in a stiff headwind. There are no lack of opportunities for this on a trip between Texas and Myrtle Beach.

When mine drops into V4, the fuel usage meter immediately improves 10, 15, 20 or 25% and sometimes more from when it's in V8. Yours should as well.

For example today on a divided hwy, I was cruising at 110kmh and on a flat section it went into V4 for a while and real time usage dropped to between 5.4 and 8.5 liters/100km which is about 28 to 44mpg US. It went like that for a few KM.

I suggest getting yours looked at.

Edited July 23, 2017 by 3beejay3

KARNUT · July 23, 2017

I'd suggest that maybe yours isn't working correctly, as it should run in V4 on flat ground & slight inclines at 72 mph and of course all downhills & it should show improved fuel economy intantaneously as soon as it switches to V4. The only exception being if you're driving in a stiff headwind. There are no lack of opportunities for this on a trip between Texas and Myrtle Beach.

When mine drops into V4, the fuel usage meter immediately improves 10, 15, 20 or 25% and sometimes more from when it's in V8. Yours should as well.

A few others on here notice no real gains in mileage when they turn theirs on. I suspect you don't have a tune where you can turn on and off the cylinder deactivation. I've had more than one vehicle with cylinder deactivation and at best have gotten 1 MPG increases with it on.

Sent from my iPhone using Tapatalk

Grumpy Bear · July 23, 2017

In my 14 GMC on my frequent trips to myrtal beach from Texas (1200 miles ) each way I didn't even gain 1 mpg with the V4 on. I had a hand held tune (hyper tec). Cruise was set at 72 MPH. What's really funny and always happens even with different vehicles I get better mileage going west than east, always with cruise on at 72.

At 72 the AFM isn't going to active. AFM is load triggered and a box car at 72 mph provides plenty of load to keep it off line unless your going down hill with a 30 mph tail wind.

Northern hemisphere prevailing winds are west to east.

People look at AFM like it's Nexium. They take it so they can continue doing what the medicine is trying to fix then wonder why it doesn't work.

Edited July 23, 2017 by Grumpy Bear

Knightfall · July 23, 2017

Almost 30k on my truck with tons of long highway trips and stop and go commutes, oil level is always perfect and I can never tell. Now, one comment I'll make has to do with the sound when you have an exhaust. My buddy's straight piped 5.7 Charger sounds "different" in 4cyl mode, but by no means worse. It still sounds like a V8 just a slightly different pitch. Are the Silverados alot different with an exhaust (or no exhaust?)?

Nanotech Environmental · July 23, 2017

At 72 the AFM isn't going to active. AFM is load triggered and a box car at 72 mph provides plenty of load to keep it off line unless your going down hill with a 30 mph tail wind.

Northern hemisphere prevailing winds are west to east.

People look at AFM like it's Nexium. They take it so they can continue doing what the medicine is trying to fix then wonder why it doesn't work.

(in bold) Umm yeah it does. FWIW- I've had mine activate at speeds in excess of 75mph on flat ground. I've also had it work with 800 lbs of cargo. AFM works and does reduce fuel usage. I'd also suggest some folks look into their driving methods as one of the causative factors in AFM not working properly..........

Nanotech Environmental · July 23, 2017

A few others on here notice no real gains in mileage when they turn theirs on. I suspect you don't have a tune where you can turn on and off the cylinder deactivation. I've had more than one vehicle with cylinder deactivation and at best have gotten 1 MPG increases with it on.

Sent from my iPhone using Tapatalk

Well.... then I'm going to have to be a bit blunt & suggest that it's you that is preventing AFM from working properly. Your driving methods and style is very likely the issue. Not the AFM.

AFM works fine for me and a whole bunch of other posters. You've said it didn't work well for you across several vehicles, so that rules out the vehicle.

You're the common denominator, so It's probably you that is preventing it from doing more than a 1 mpg improvement.. Sorry.

I've seen this happen lot's of times when the subject of fuel economy pops up. A few guys complain that their particular vehicle doesn't get good mileage, or get near the expected mileage, meanwhile a whole bunch of others all with the same vehicle get the expected mileage, or better.

It's almost always driving style and methods that causes the poor mileage, not the vehicle.

Over the years, I've watched many of those same complainers drive and it quickly becomes apparent why their mileage is so bad. It's their driving style pure and simple.

KARNUT · July 23, 2017

Well.... then I'm going to have to be a bit blunt & suggest that it's you that is preventing AFM from working properly. Your driving methods and style is very likely the issue. Not the AFM.

AFM works fine for me and a whole bunch of other posters. You've said it didn't work well for you across several vehicles, so that rules out the vehicle.

You're the common denominator, so It's probably you that is preventing it from doing more than a 1 mpg improvement.. Sorry.

I've seen this happen lot's of times when the subject of fuel economy pops up. A few guys complain that their particular vehicle doesn't get good mileage, or get near the expected mileage, meanwhile a whole bunch of others all with the same vehicle get the expected mileage, or better.

It's almost always driving style and methods that causes the poor mileage, not the vehicle.

Over the years, I've watched many of those same complainers drive and it quickly becomes apparent why their mileage is so bad. It's their driving style pure and simple.

Thats a good one I must have figured out a way to cook the books as they say. Theirs too many added moving parts to fail with cylinder deactivation for what's gained. I use a hand held tune with most of my vehicles, so it was easy to turn off and on the cylinder deactivation just for an easy comparison. I,like most people who travel generally drive with an eye toward gas mileage and use cruise control as often as possible. So the interest was to see how much better gas mileage would be with it on verses off. If anything I was being less aggressive with it on. Most of time at highway speeds over the same stretch of road.

Sent from my iPhone using Tapatalk

Edited July 23, 2017 by KARNUT

Grumpy Bear · July 23, 2017

(in bold) Umm yeah it does. FWIW- I've had mine activate at speeds in excess of 75mph on flat ground. I've also had it work with 800 lbs of cargo. AFM works and does reduce fuel usage. I'd also suggest some folks look into their driving methods as one of the causative factors in AFM not working properly..........

Well I can see the difference right away. I don't have much flat ground and around here, Chicago area big wind is life. That said. Being on and staying on is quite something else. Yea, it turns on but it has to say on enough to add it's contribution to the tanks fuel usage. Being on down hill when the fuel map says 'off' or 135 mpg doesn't add anything to something already using nothing.

As for cargo and staying on; once your rolling cargo doesn't take any extra energy. It's take extra to accelerated it and to slow it. But not at steady speed.

Karnut's tuner may turn on and off the ability of the AFM to active but it can't make it turn on if the base map is saying no. Simply saying on doesn't make it turn on. So if driving style or conditions dictate the AFM is naturally off make this point mute. Don't know if I'm being clear there but.....

Lets nut shell this. Conditions dictate it's usefulness. Those conditions include prevailing weather. Topography. Your right foot and mind set and personal choices. The trucks condition and layout. and so on. There is no blanket statement that fits all cases. It works period. It being useful to your situation is something else.

Too complicated? Roller cams are complicated in design and execution. So is VVT and computer controlled vacuum advance and all give your motor the ability to make a torque curve as flat as a billiard table. Rhodes lifters have been in use for decades. AFM is just a switchable bleed down Rhodes with more range. Not that complicated.

Being I'm in the mood. The early issue of AFM with the oil redirect. Saying that this caused rings to 'gum up or plug up" needs some thought. Nope...it doesn't...they were being flooded beyond their ability to control the volume. If they found any plugged flooding wasn't the reason. You can't gum up a ring with volume. You can however do so by cooking the oil to varnish. That is not the fault of the AFM. They made the right correction. Redirect it.

This is entertaining though. Like watching two dogs fight over which end of the rag taste better.

Edited July 23, 2017 by Grumpy Bear

KARNUT · July 23, 2017

Well I can see the difference right away. I don't have much flat ground and around here, Chicago area big wind is life. That said. Being on and staying on is quite something else. Yea, it turns on but it has to say on enough to add it's contribution to the tanks fuel usage. Being on down hill when the fuel map says 'off' or 135 mpg doesn't add anything to something already using nothing.

As for cargo and staying on; once your rolling cargo doesn't take any extra energy. It's take extra to accelerated it and to slow it. But not at steady speed.

Karnut's tuner may turn on and off the ability of the AFM to active but it can't make it turn on if the base map is saying no. Simply saying on doesn't make it turn on. So if driving style or conditions dictate the AFM is naturally off make this point mute. Don't know if I'm being clear there but.....

Lets nut shell this. Conditions dictate it's usefulness. Those conditions include prevailing weather. Topography. Your right foot and mind set and personal choices. The trucks condition and layout. and so on. There is no blanket statement that fits all cases. It works period. It being useful to your situation is something else.

Too complicated? Roller cams are complicated in design and execution. So is VVT and computer controlled vacuum advance and all give your motor the ability to make a torque curve as flat as a billiard table. Rhodes lifters have been in use for decades. AFM is just a switchable bleed down Rhodes with more range. Not that complicated.

Being I'm in the mood. The early issue of AFM with the oil redirect. Saying that this caused rings to 'gum up or plug up" needs some thought. Nope...it doesn't...they were being flooded beyond their ability to control the volume. If they found any plugged flooding wasn't the reason. You can't gum up a ring with volume. You can however do so by cooking the oil to varnish. That is not the fault of the AFM. They made the right correction. Redirect it.

This is entertaining though. Like watching two dogs fight over which end of the rag taste better.

I did my test on the same stretch of I-10 while I was already at cruise speed 72 mile per hr. over several cross country trips. I was thinking of putting exhaust on and turning off cylinder deactivation for sound reasons. If there was real fuel mileage gains with it on, there would have been no exhaust changes. As it turns out all of the sudden exhaust sounds (after 40 years) became annoying and I went back to quiet.

Sent from my iPhone using Tapatalk

dorkweed · July 23, 2017

I use the Range AFM delete on Interstate trips....................I'm leary of AFM to function much more than 100,000 miles effectively. And I don't like the idea of cylinders not firing/coasting along................as I believe the engine will wear in/out unevenly over time.

That said; if I keep my speeds under 70mph on the Interstates, I can still pull 21-22+mpg (HAND CALCULATED FOR THE WHOLE TANK) in 100% V-8 mode.

One trip running North on I-95 from FL thru GA thru SC; I pulled 22+mpg running 80+mph with a 10-15mph wind at my back............it's a rare occurrence that I have the wind at my back when traveling.............took advantage of it there!!!

Bowtie Billy Hill · July 24, 2017

I've had (allegedly) three Silverados with 5.3 AFM engines. I say allegedly because my '08 had AFM listed on the window sticker, but that's as close as I ever came to it. I don't believe the AFM ever kicked in on that truck in the three years that I had it, and I averaged about 13.5 mpg all the time with it. My '14 had the newer 5.3, which is a whole different animal than the engine in my '08. I just turned it in with 30k miles on it, and AFM never caused me a single issue. It did, however, help me average roughly 16 mpg running the same route everyday that I did in my '08. I'm not going to argue with 2.5-3 mpg more. The 4/8 cylinder transition was smooth in that truck, and I was the only one who could pick up on a very quiet chirp that it would make going back into 8 cylinder mode...and only if it was quiet in the truck. My new '17 has the exact same setup. The transitions seem even smoother, and the AFM seems to activate even easier in this truck. I'm already averaging about a half mpg more in the new truck under identical conditions, and it only has 650 miles on it. No tiny chirp in this one, either. I've never used a drop of oil in any of my trucks, or had any AFM related issues. Go for it, and warranty the crap out of it if you would happen to get a bad one.

mookdoc6 · July 24, 2017

I've had (allegedly) three Silverados with 5.3 AFM engines. I say allegedly because my '08 had AFM listed on the window sticker, but that's as close as I ever came to it. I don't believe the AFM ever kicked in on that truck in the three years that I had it, and I averaged about 13.5 mpg all the time with it. My '14 had the newer 5.3, which is a whole different animal than the engine in my '08. I just turned it in with 30k miles on it, and AFM never caused me a single issue. It did, however, help me average roughly 16 mpg running the same route everyday that I did in my '08. I'm not going to argue with 2.5-3 mpg more. The 4/8 cylinder transition was smooth in that truck, and I was the only one who could pick up on a very quiet chirp that it would make going back into 8 cylinder mode...and only if it was quiet in the truck. My new '17 has the exact same setup. The transitions seem even smoother, and the AFM seems to activate even easier in this truck. I'm already averaging about a half mpg more in the new truck under identical conditions, and it only has 650 miles on it. No tiny chirp in this one, either. I've never used a drop of oil in any of my trucks, or had any AFM related issues. Go for it, and warranty the crap out of it if you would happen to get a bad one.

I hear ya about the AFM and I am sure there were problems associated with it on previous Vortec's as I have seen the oil consumption first hand but not entirely convinced that AFM was absolute cause on those engines and a couple things were being played in conjunction.

But when I get 22.7mpg driving through western states and large passes I soon enjoy that "AFM" and V8 because that is going to keep V8'S in GM's stable. The next rendition is even more complicated and removes the uneven wear aspect from the equation the other poster eluded to.

I see GM getting 5.3 to just shy of 400hp and 420tq with 10speed and dynamic displacement technology and throwing down 25mpgs all day long on hwy and 18 city.......serious shit folks!

you can poo,poo this all you want but you can't even net 22mpg's on HWY with a 2.7 ecoboost but hey "FERD" is the engineering marvel of the world........how about water injection?

Edited July 24, 2017 by mookdoc6

Nanotech Environmental · July 24, 2017

Thats a good one I must have figured out a way to cook the books as they say. Theirs too many added moving parts to fail with cylinder deactivation for what's gained. I use a hand held tune with most of my vehicles, so it was easy to turn off and on the cylinder deactivation just for an easy comparison. I,like most people who travel generally drive with an eye toward gas mileage and use cruise control as often as possible. So the interest was to see how much better gas mileage would be with it on verses off. If anything I was being less aggressive with it on. Most of time at highway speeds over the same stretch of road.

Sent from my iPhone using Tapatalk

What you have established isn't that AFM only gets 1 mpg better than running without it, but rather that it only gets 1 mpg better while you are behind the wheel. Other people get different results. In many situations, cruise control can result in much worse fuel econ, than driving without it.

Many people think they are driving for fuel econ, when in reality they aren't. People engage in in all kinds of unconcious behaviors and actions that they simply aren't aware of. It's part of the human condition. We all do it in some way shape or form.

For example, I personally know of 3 people that cannot, or will not hold a steady speed on the highway. Sometimes so bad that passengers get nauseous. Yet these 3 people are completely oblivious to it and also in denial of it. They resist all suggestions to look at, or re-consider their driving style/methods. They also get abominal fuel mileage & blame their vehicles.

It was quite an eye opener when I drove one of the persons cars on a trip one time & got almost 200 km more on a tank of fuel than what he'd previously been able to achieve. He marveled at it & couldn't understand how I was able to do it. To add insult, I was not even driving for fuel economy and was driving at speeds of 80+ mph to make up time we had lost while stuck in traffic(another fuel mileage killer) near the start of the trip. The car was also fully laden with 4 adults, luggage and beer.

Edited July 24, 2017 by 3beejay3

KARNUT · July 24, 2017

What you have established isn't that AFM only gets 1 mpg better than running without it, but rather that it only gets 1 mpg better while you are behind the wheel. Other people get different results. In many situations, cruise control can result in much worse fuel econ, than driving without it.

Many people think they are driving for fuel econ, when in reality they aren't. People engage in in all kinds of unconcious behaviors and actions that they simply aren't aware of. It's part of the human condition. We all do it in some way shape or form.

For example, I personally know of 3 people that cannot, or will not hold a steady speed on the highway. Sometimes so bad that passengers get nauseous. Yet these 3 people are completely oblivious to it and also in denial of it. They resist all suggestions to look at, or re-consider their driving style/methods. They also get abominal fuel mileage & blame their vehicles.

It was quite an eye opener when I drove one of the persons cars on a trip one time & got almost 200 km more on a tank of fuel than what he'd previously been able to achieve. He marveled at it & couldn't understand how I was able to do it. To add insult, I was not even driving for fuel economy and was driving at speeds of 80+ mph to make up time we had lost while stuck in traffic(another fuel mileage killer) near the start of the trip. The car was also fully laden with 4 adults, luggage and beer.

In the 40 years of driving 50K plus miles a year with my business I think I got cruise control down. The thing that I dislike the most is GM took a 300K miles engine added more moving parts for very little benefit. The results (its already happening) at around 100K miles these added parts start failing. The thousands that it cost to repair could've gone in the gas tank. I've bought my trucks for work and durability not to squeeze a few extra miles per gallon. Retired now I take my trips in a Camry for comfort, gas mileage, and reliability. For trips to Home Depot I take my reliable pristine 92 Chevy p/u. Still running R-12 in the AC, wonder how many magic 8-4cylinder 5.3s will be running 25years from now.

Sent from my iPhone using Tapatalk

Nanotech Environmental · July 24, 2017

In the 40 years of driving 50K plus miles a year with my business I think I got cruise control down. The thing that I dislike the most is GM took a 300K miles engine added more moving parts for very little benefit. The results (its already happening) at around 100K miles these added parts start failing. The thousands that it cost to repair could've gone in the gas tank. I've bought my trucks for work and durability not to squeeze a few extra miles per gallon. Retired now I take my trips in a Camry for comfort, gas mileage, and reliability. For trips to Home Depot I take my reliable pristine 92 Chevy p/u. Still running R-12 in the AC, wonder how many magic 8-4cylinder 5.3s will be running 25years from now.

Sent from my iPhone using Tapatalk

Very little benefit? Many see significant benefits.

You still seem to miss the fact that your personal experience isn't reflected by the majority, or that your results aren't necessarily due to the vehicle itself, or the design of the engine etc..........

I can't comment on repair costs, or durability as those still remain to be seen. If you lived in the salt belt you wouldn't be driving anything that's 25 yrs old unless it was stored every winter. Consider yourself fortunate that you can drive a vehicle til it wears out mechanically rather than rust eating it away on you.

Edited July 24, 2017 by 3beejay3