Exhausted/ AFM Advice

Blaze2289 · May 23, 2019

I am trying to figure out the best route to go with my 18 5.3 exhaust. I keep seeing that the AFM makes most exhaust changes sound pretty bad. Just curious what y'all's advice is. I have a hypertech tuner coming in so I can turn off the AFM but I'm wondering how many MPGs I'll lose if I do that.

dieselfan1 · May 23, 2019

I put a Borla S Type catback exhaust on my 2018 5.3 crew cab standard bed 4x4 a little over a month ago and with the AFM on it droned pretty bad around 1500 rpm. I put a Range AFM disabler on it and the drone is gone. And after around 1500 miles I'm noticing a little over 1 mpg improvement. My guess is the exhaust helped mostly to get that 1+ mpg though.

IMO AFM is worthless.

Edited May 23, 2019 by dieselfan1

amxguy1970 · May 23, 2019

Some will say you will lose nothing, but reality is you will lose something. How much depends on how often it switches modes with your driving style and location. It is easy to see the mpg jump up on a flat surface when it switches over. GM wouldn't have spent so much time and money if there weren't improvements (especially adding it to their sports cars). If I were to venture a guess I would say 0.5+/- mpg overall. Maybe a little less or more if you spend more time on the highway or city...

Tyler

mitchely03 · May 23, 2019

heres my exahust setup, check out the description for what i have done.

3tspapat · May 23, 2019

it really depends on the type of driving you do. City and hilly areas vs long flat roads, highways, etc. when there is little load or acceleration involved.

My driving is typically stop and go and some long stretches. I tested it with AFM on and Off (using the manual mode) and for me, it didn't make too much of a difference. The biggest difference was not being able to use 8th gear when I override AFM by using L7 mode. I did a comparison sometime ago in of the MPG posts or AFM post. I can't remember. I need to go back to it to compare how the range is doing for me.