AFM disabler and mpg?

[Caligirl]

Been searching but couldn't find the answer....I'm probably going to be doing city (mountain) mileage for most of my driving accept for occasional road trips, so how much mpg can I expect to realistically get with the disabler installed vs AFM active on a 2007 Tahoe 4wd LMG? Will I still get 20 mpg hwy without AFM active? I expect mountain driving to be on the low end. Right now it switches back and forth between V8 and V4 every couple of minutes in my regular drive. Thanks!

 

[iamdub]

How much it will affect depends on how much it's actually engaged. When I had mine tuned out, I lost .5 - 1 MPG in my usual areas of travel. There are so many stars that need to align for AFM to be of any benefit: Long stretches of flat and straight road, no headwind, speeds under 70MPH, no traffic, dead-still foot or use of cruise control, etc. EVEN IF your driving scenarios manage to keep AFM engaged for the majority of the time, the amount saved in fuel won't ever compare to the cost of the damage that can be done if there's a failure within the system. That ~1, maybe 2 MPG you lose from disabling or deleting it is mere pennies. It won't be missed. BTW, since I deleted AFM with a performance cam and other upgrades, I'm now averaging the same or better MPG as I did with a stock engine and AFM.

 

[Caligirl]

How much it will affect depends on how much it's actually engaged. When I had mine tuned out, I lost .5 - 1 MPG in my usual areas of travel. There are so many stars that need to align for AFM to be of any benefit: Long stretches of flat and straight road, no headwind, speeds under 70MPH, no traffic, dead-still foot or use of cruise control, etc. EVEN IF your driving scenarios manage to keep AFM engaged for the majority of the time, the amount saved in fuel won't ever compare to the cost of the damage that can be done if there's a failure within the system. That ~1, maybe 2 MPG you lose from disabling or deleting it is mere pennies. It won't be missed. BTW, since I deleted AFM with a performance cam and other upgrades, I'm now averaging the same or better MPG as I did with a stock engine and AFM.

That's good to hear. I figured I'd not be getting much everyday benefit from AFM with the winding roads and up and down hills on my "big" 15 miles of driving each day. After looking at what folks want for a 2011 or 2012 with similar mileage with less AFM issues, I think putting money into this 2007 will still be cheaper.

 

[avalonandl]

The Range disabler is about $200. I use it, you lose about 0.5 mpg....

 

[wsteele]

The Range disabler is about $200. I use it, you lose about 0.5 mpg....

My experience pretty much exactly.

 

[iamdub]

That's good to hear. I figured I'd not be getting much everyday benefit from AFM with the winding roads and up and down hills on my "big" 15 miles of driving each day. After looking at what folks want for a 2011 or 2012 with similar mileage with less AFM issues, I think putting money into this 2007 will still be cheaper.

Your short commute and terrain makes having AFM even less valuable. With the low mileage your Tahoe has and with taking a few smart proactive measures, it should be a reliable and useful vehicle for a long time. You got a good deal on it, wisely invest a little and keep it a good deal.


The short list if it were mine:

(1) Have AFM tuned out. I prefer the tune method over a plug-in because it's cheap, permanent, doesn't screw with a bunch of other stuff for when it's time for your inspections, doesn't occupy the ALDL port and doesn't drain your battery.

(2) Remove the driver side valve cover to see if it's the updated one and replace it if not.

(3) Check the numbers engraved on the front edge of the VLOM to see if it's the updated one. It doesn't matter if it's not since AFM will be disabled, but you'd wanna know just to get an idea if the system has ever been serviced.

(4) Get a GOOD tune. You can tie this one in with having AFM turned off. There are so many benefits with a tune that would prolong the life of the 4L60E as well as improve the responsiveness. Speaking of trans, I'd recommend the installation of a Corvette servo.

 

[Caligirl]

Your short commute and terrain makes having AFM even less valuable. With the low mileage your Tahoe has and with taking a few smart proactive measures, it should be a reliable and useful vehicle for a long time. You got a good deal on it, wisely invest a little and keep it a good deal.


The short list f it were mine:

(1) Have AFM tuned out. I prefer the tune method over a plug-in because it's cheap, permanent, doesn't screw with a bunch of other stuff for when it's time for your inspections, doesn't occupy the ALDL port and doesn't drain your battery.

(2) Remove the driver side valve cover to see if it's the updated one and replace it if not.

(3) Check the numbers engraved on the front edge of the VLOM to see if it's the updated one. It doesn't matter if it's not since AFM will be disabled, but you'd wanna know just to get an idea if the system has ever been serviced.

(4) Get a GOOD tune. You can tie this one in with having AFM turned off. There are so many benefits with a tune that would prolong the life of the 4L60E as well as improve the responsiveness. Speaking of trans, I'd recommend the installation of a Corvette servo.

Thanks much! I think I'll screenshot this response and give it to my husband as my laundry list haha.

I'm so appreciative of all of the assistance; it makes me feel better about keeping it. With this old of a vehicle, I was really hesitant to begin with, but I now know that not as many things could go wrong (beyond the normal wear and tear of an older vehicle) than I thought. Was getting red flags from reading the doom and gloom about the 2007, but sounds like worth it in the long run to get a reliable vehicle on the cheap.

Heck my husband's coworker got a brand new GM truck in 2016 and has already had to replace the transmission last year and had all kinds of problems and that's with a $50000 truck! I know it was under warranty, but still I think I'd rather invest a thousand into this one than wondering if my new vehicle is going to crap out AFTER warranty.

 

[Sparksalot]

The Range disabler is about $200. I use it, you lose about 0.5 mpg....

I’ve got one in each twin, and honestly haven’t noticed any difference.

 

[iamdub]

Thanks much! I think I'll screenshot this response and give it to my husband as my laundry list haha.

I'm so appreciative of all of the assistance; it makes me feel better about keeping it. With this old of a vehicle, I was really hesitant to begin with, but I now know that not as many things could go wrong (beyond the normal wear and tear of an older vehicle) than I thought. Was getting red flags from reading the doom and gloom about the 2007, but sounds like worth it in the long run to get a reliable vehicle on the cheap.

Heck my husband's coworker got a brand new GM truck in 2016 and has already had to replace the transmission last year and had all kinds of problems and that's with a $50000 truck! I know it was under warranty, but still I think I'd rather invest a thousand into this one than wondering if my new vehicle is going to crap out AFTER warranty.

I think there's so much negativity more specific to the '07 since that was the first year for the new design and for AFM, so everyone put it under a microscope and heavily criticized it.

My opinion is that the Gen 3 engine ('99-'07.5, the '07.5+ is a Gen 4) is the most reliable GM small block ever. The Gen 4 has upgraded components for durability, power output and efficiency, but AFM counters this. Take AFM outta the equation and you'll have a better engine than the Gen 3, as it should be. I believe the reliability of the vehicles as a whole has gotten worse since.

Mine is an '08, so it's virtually identical to your '07. I bought it with 146K miles, had AFM turned off around 160K-170K (estimating) to solve a shuddering problem and beat on it from there on. At 200K, after a night at the racetrack to get some baselines, I pulled the engine to refresh it since I didn't plan on keeping it forever but I wanted to delete AFM and have a good look at the internals. Compression was great, cylinder walls and bearing surfaces looked great and there wasn't a speck of sludge to be found. I replaced the critical wear items (oil pump, timing chain, etc.) along with the AFM delete. This turned into a performance cam, higher compression and a few other small mods. Not long after it was back on the road, I took the family on an 1,800+ mile trip to Tampa, averaging 19 MPG at 70 MPH, fully loaded and towing a small trailer. Coming back from Tampa, I towed a 1,000 lb. golf cart on that trailer and even more on board and averaged 17 MPG cruising at 70 MPH.

My point is that if you adhere to maintenance, take a few proactive measures and keep clean oil in it, you'll see that these are strong and reliable rigs and the internet negativity is blown out of proportion.

 

[Joseph Garcia]

Buy a Chinese knockoff Tech 2 unit for about $350, and you can disable the AFM on the truck, and you will have a top notch scanning and programming tool that will pay for itself many times over, for the life of the truck.

 

[1BADI5]

With the AFM/VVT delete, cam/heads/exhaust, 3.73 gears and a 3200 stall converter I'm still getting 19.5mpg on the highway.

Delete it all and enjoy the drive!

 

[Caligirl]

So after deleting AFM and reinstalling ECM, the display stays on V8 but when going downhill or straightaways, it still says 99mpg (like it used to when getting ready to switch to V4). I'm assuming this is because the dash display control doesn't know how to "read" non DOD setup? Anyone else experience that?

 

[wsteele]

So after deleting AFM and reinstalling ECM, the display stays on V8 but when going downhill or straightaways, it still says 99mpg (like it used to when getting ready to switch to V4). I'm assuming this is because the dash display control doesn't know how to "read" non DOD setup? Anyone else experience that?

My AFM was turned off a while ago in the ECM using a Diablo Predator (essentially flashing the ECM with everything that was there before, but with AFM disabled), I suspect exactly the same way the tuner disabled AFM in your ECM (PCM), just with a different application.

My DIC displays only V8 mode as well, but my instantaneous mileage looks about right for the mode and RPM I am in, that is, going downhill foot off the accelerator I might see 40-50+ MPG, constantly climbing as the time passes with my foot off the gas. When I get to the bottom of the incline and start up the other side foot back on the gas, it might jump back to single digits for a time.

I can't say I have ever seen 99+, whether in AFM mode or after it was disabled, but I only glance at it occasionally when I am interested, many times I don't even have that DIC page up, so maybe 99+ is displayed and I just didn't see it.

 

[avalonandl]

So after deleting AFM and reinstalling ECM, the display stays on V8 but when going downhill or straightaways, it still says 99mpg (like it used to when getting ready to switch to V4). I'm assuming this is because the dash display control doesn't know how to "read" non DOD setup? Anyone else experience that?

The mpg is relative, has nothing to do with V4. The engines will cut fuel flow when coasting thus 99+ mpg....

 

[wsteele]

So after deleting AFM and reinstalling ECM, the display stays on V8 but when going downhill or straightaways, it still says 99mpg (like it used to when getting ready to switch to V4). I'm assuming this is because the dash display control doesn't know how to "read" non DOD setup? Anyone else experience that?

Just an update. I took the Yukon out on some errands this morning and watched the DIC most of the time. Even on very steep downhill's, going say 40 mph and foot off the pedal for an extended period of time, I never saw 99+ mpg. I suspect I would have to be traveling on an extended fairly steep downhill at pretty high speeds to see 99+ on the DIC (think some stretches of I80 coming down from Donner).

If you are seeing 99+ mpg on flat stretches, when you are off the gas, maybe he tuned it some, as well as disabling AFM. Just SWAG.

 

[Caligirl]

Just an update. I took the Yukon out on some errands this morning and watched the DIC most of the time. Even on very steep downhill's, going say 40 mph and foot off the pedal for an extended period of time, I never saw 99+ mpg. I suspect I would have to be traveling on an extended fairly steep downhill at pretty high speeds to see 99+ on the DIC (think some stretches of I80 coming down from Donner).

If you are seeing 99+ mpg on flat stretches, when you are off the gas, maybe he tuned it some, as well as disabling AFM. Just SWAG.

It was doing the 99+ before deleting. But as AvalonandI already mentioned, it may be just that fuel is cut when coasting. I thought it was odd when I first saw it and thought it was the transition between V4 and V8, but maybe it is just "normal" for my vehicle.

 

[iamdub]

MPG is calculated by engine load, injector duty cycle, vehicle speed and time. I don't have any real hills in my area, at least none long enough to take a decline at highway speeds to get a super high MPG readout on the DIC.

How fast are you going on these downhills? Regardless, your AFM is inactive if the DIC is displaying "V8". Also, your DFCO (Deceleration Fuel Cut Off) may be enabled.

 

[Idriveaho]

That’s normal readings. My equinox with the 4cyl does the same thing.

 

[Caligirl]

MPG is calculated by engine load, injector duty cycle, vehicle speed and time. I don't have any real hills in my area, at least none long enough to take a decline at highway speeds to get a super high MPG readout on the DIC.

How fast are you going on these downhills? Regardless, your AFM is inactive if the DIC is displaying "V8". Also, your DFCO (Deceleration Fuel Cut Off) may be enabled.

50-60 mpg on downhill hwy-oops mph haha

 

[iamdub]

50-60 mpg on downhill hwy

I assume you meant "mph". 55-60 mph will cover a lot of distance in an hour. Coasting downhill at that speed will consume an extremely small amount of fuel, even when running on eight cylinders. If you were on that same hill, at that same speed for an hour, you'd get 99+ miles per gallon.