Results From Disabling Afm

slomo007 · October 6, 2009

I had Justin disable my AFM about a month ago (adjusted a previous tune). I was nervous about doing this because it just didn't make sense when I had read that other people were not seeing a mileage difference after disabling it, but the exhaust drone was obvious when combined with the Borla GMPP performance exhaust so I decided to give it a shot.

First, the positive. The exhaust drone is completely gone obviously. Plus, as an added benefit, I had NO idea how much AFM affects the driveability of these trucks. It feels so much more responsive that it is just amazing to me. Also, I am planning on keeping this truck well past 100,000 miles and I don't want to take any chances about the durability of the AFM system.

The negative.....I did lose about 1 MPG overall. With AFM active, I was getting 16.5-17 city and 18 highway. Now, I'm getting 16-16.5 city and 17-17.5 highway (driving 75 MPH +). I have a 5.3L with a 3.42 rear end, with a leveling kit and 265/70/18 tires.

Overall, I'm fairly happy with the decision. Mileage is very important to me, so I'm surprised that I'm this happy....but that just goes to show you how much of a difference there is in the performance of the truck now.

My suggestion, is that unless you all you care about is gas mileage (and if this is the case you shouldn't get a tune - it doesn't do much for mileage really) then you should disable AFM, or at least try it to see how you like it.

redsled2007 · October 6, 2009

If gas milage is THAT important to you, why are you going 75+ mph? That's got to be at least 2-3 mpg depending on how far on the plus side you're going.

slomo007 · October 6, 2009

If gas milage is THAT important to you, why are you going 75+ mph? That's got to be at least 2-3 mpg depending on how far on the plus side you're going.

Because I live in Texas.

C. Charles Hahn · October 6, 2009

If gas milage is THAT important to you, why are you going 75+ mph? That's got to be at least 2-3 mpg depending on how far on the plus side you're going.

In Texas you have 80 MPH speed limits.

Seriously? Damn, I'd be setting cruise at 85-90 on a regular basis

asilverblazer · October 6, 2009

as an added benefit, I had NO idea how much AFM affects the driveability of these trucks. It feels so much more responsive that it is just amazing to me.

Are you sure this is just from disabling the AFM and not the tune in general?

slomo007 · October 6, 2009

as an added benefit, I had NO idea how much AFM affects the driveability of these trucks. It feels so much more responsive that it is just amazing to me.

Are you sure this is just from disabling the AFM and not the tune in general?

Sure.

I already had the tune, just disabled AFM. He did make some slight adjustments to the tune to get rid of some engine pinging but nothing too major.

txab · October 6, 2009

If gas milage is THAT important to you, why are you going 75+ mph? That's got to be at least 2-3 mpg depending on how far on the plus side you're going.

In Texas you have 80 MPH speed limits.

Certain areas do. Most are 70 and below

cerbomark · October 6, 2009

Mine looks about 1 mpg better or a least even with my afm off and 87 octane tune. 1 mpg change could be anything like a big enough outside temp change or slightly differnt fuel or many other small variables. I live in very hilly road conditions which IMO negates the afm. I agree, turning it off is worth it. This is my second afm motor that I liked better turned off.

2005LT · October 6, 2009

I've had mine off for about 2 tanks now. Can't say for sure yet whether there is a mileage difference or not. My mileage has gone down lately, but I've been driving it with 'more authority' lately plus the outside temps have dropped quite a bit in the last week or two.

I was getting tired of it switching between V8 and V4 all the time at constant speed. The driveablility has improved by turning AFM off.

Spurshot · October 6, 2009

Darral

That picture doesn't look like any mountains I've seen in TX. Pikes Peak?

Stex · October 6, 2009

If gas milage is THAT important to you, why are you going 75+ mph? That's got to be at least 2-3 mpg depending on how far on the plus side you're going.

Because I live in Texas.

I think he does not mean the speed limit but the distance we have to cover down this way...in stex .....bird hunting can be 100 miles one way easy, fishing the coast 150- 200, south tex deer 150, hill country hunting 100 etc...just going to town maybe 25...??

I think .5 to 1mpg loss sounds about right with afm off...65 mph does save a lot of gas but man it can make for what seems like a long ride...not to mention being run over

tonygxp · October 6, 2009

I don't know if it's the 6spd trans or what but my new tahoe with the 6spd trans is beating the Sierra by at least 1.5mpg. and that's with me idling the tahoe for 10-15min multiple times the first 3 days i had it and driving it hard.. city 150mi and 2 pkwy trips at 75-80 for about 40miles shows 15.2 on the dic. getting the tahoe tuned today or tomorrow. thinking of utilizing the V4 more have you tried that yet?

txab · October 6, 2009

Darral
That picture doesn't look like any mountains I've seen in TX. Pikes Peak?

Close. Longs Peak in Co.

Bowtie2Sierra · October 6, 2009

Most of the posts I have read about turning AFM off had to do with the difference (or lack of) in mpg and not much mention about the driveability. The increased driveability mentioned by others in this thread definitely cause me to think about turning mine off now. AFM has been seemless in my truck so I've been indifferent to it.