[KingLT1]

Originally Posted by SuperSound

AFM can still be active in manual mode. I did some experimenting and found out the key to keeping it off is to actually do a manual downshift while in manual mode. Simply letting the computer downshift, then you manually upshifting will still enable AFM. Not saying you still had AFM enabled, just for reference for anyone wondering.

It only activates the first time I drive it letting the computer down shift. After that it's off all the time...I don't have to manual down shift to disable it. Kind of odd imo.

Originally Posted by jdasnt3

AFM doesn't help with fuel economy on the highway? I thought it did by switching over to V4. I'm not talking about driving around town.

No...I get 32-34mpg @ 70mph in V8 mode. AFM is not needed with a 8 speed automatic that has 2.77 gear ratio. These cars are only turning 2k rpm @ 90 mph in 8th gear...it's silly.

[jdasnt3]

When I talk about MPG, I am talking about the 50 mile averages my DIC shows. Pre-mods, the best I got on the interstates (all flat here in FL) was 28ish. Now I can get 31 or so with 91 octane, but only 22 with E85.

So there are some on here who are quoting 36MPG? How? I can snap a quick picture of my DIC showing 99MPG while coasting. And I haven't seen any proof that AFM doesn't help. I'm asking for somebody to do a scientific type study and show that it is worthless, and if it is, let's talk to GM and get them to save a bunch of money by eliminating it altogether. Why is it being installed in these cars if it doesn't do anything for fuel economy?

If it is proven to be worthless, I'll have mine tuned out after my headers and retune this Winter.

[SuperSound]

Originally Posted by KingLT1

It only activates the first time I drive it letting the computer down shift. After that it's off all the time...I don't have to manual down shift to disable it. Kind of odd imo.

I think we are describing the same behavior in different ways. I only have to manually downshift once to keep AFM off for the remainder of the trip (if I leave the shifter in the manual gate). The second I put the shifter back in D, AFM will engage again. The programming is definitely wonky. One would think it would have been easier to just program AFM off in manual mode period.

Originally Posted by jdasnt3

When I talk about MPG, I am talking about the 50 mile averages my DIC shows. Pre-mods, the best I got on the interstates (all flat here in FL) was 28ish. Now I can get 31 or so with 91 octane, but only 22 with E85.

So there are some on here who are quoting 36MPG? How? I can snap a quick picture of my DIC showing 99MPG while coasting. And I haven't seen any proof that AFM doesn't help. I'm asking for somebody to do a scientific type study and show that it is worthless, and if it is, let's talk to GM and get them to save a bunch of money by eliminating it altogether. Why is it being installed in these cars if it doesn't do anything for fuel economy?

If it is proven to be worthless, I'll have mine tuned out after my headers and retune this Winter.

My 36.6mpg was on the last 25mi setting. I believe on last 50mi, it reads 34mpg as my best. Both of those numbers are with AFM. I personally don't believe anyone will beat those numbers with AFM off. Will they get within 1 to 2 mpg? I could see that, but that's all the improvement AFM is supposed to give anyway. And the reality is normal driving situations probably do not show the real benefits of it. You pretty much have to be in a sustained speed cruise for a long enough distance for the mpg gauge to show it. It's gains on a full tank with normal mixed driving of city/highway, will probably show little gain.

That said, this Friday I will be taking the same route I hit my 36.6mpg previously. I will make an effort to use manual mode and get a number with AFM off. The temps will be different, but if traffic is light I should get a good comparison number.

[cellsafemode]

afm only matters on cruising long stretches of highway driving. It doesn't do anything on city driving since you're almost never in the situations that afm is allowed to activate.

it works and certainly makes a difference.

There are definitely products that turn it off without issue, I have a Trifecta tune that allows me to turn it on and off at will by switching between sport and touring mode. Touring on, sport off. No negative side-effects. Best of both worlds.