jimman

I was concerned about longevity but I have a rep in Minneapolis with a Chrysler product with over 250,000 miles and it works fine and has no problems. As far as sound is concerned I can't hear it, do you run along side or what.

westman

Is it possible to tune out the AFM valves without deactivating the AFM?

xp800

IMO, there is absolutely no reason to do this. Even if it were possible to tune out the AFM valve closure, the car sounds like absolute a$$ when in V4 mode and the AFM valves open. No performance advantage in keeping them open when in V4 either.

Try it for yourself. Pull the AFM valve (fuse #32) and the NPP fuse (either #41 or #42). Pulling the AFM fuse will trigger a CEL, but you can hear what crap it sounds like. The CEL will reset after 4-5 start-stop cycles. The NPP fuse doesn't trigger a CEL.

red 1

You can buy a Range disabler like I did to keep the engine in V8 mode all of the time.

Boiler_81

Yes indeed, best NPP AFM valve thread on this site. I have referred a lot of people to it. The information is correct and up to date.

westman

It's a long story full of pain and suffereing...

xp800

Yeah, I figured out why you asked your question... Your Borla exhaust right?

I can't recall if the valve logic resides in the BCM or CCM, but there there is a functional check of the actuators on every start cycle. The AFM valves must "see" a very precise feedback force from the valve springs as well as excursion limits. If these parameters are out of range for the AFM actuators (like having the valves plugged in but no reactive spring load), you will get a CEL. This is the case with the Borla exhaust you have. There's nothing in the "fake" valves it presents to the AFM actuators.

The NPP valves are not as tightly monitored, and removing them by fuse pull or connector disconnect will not cause a CEL. I have read in other owner reports that if they get stuck (corrosion/ice) that you can get a CEL.

I don't know if you disable AFM function through a tune (or AFM disable device like Range Technology) whether it then bypasses the actuator check that causes the CEL. Maybe someone here can chime in on that.

The only non-tune solution I have seen (and it's not elegant) if you want to KEEP your AFM mode during driving is to cut the AFM valves out of your OEM exhaust, leave them attached to the actuators, and tie them up out of the way.

westman

You are correct in your assumption about the borla exhaust. Going off the recommendations of a Borla tech, the result has been an absolute nightmare trying to get the system to work with the computer. The car does sound like absolute @ss when switching between AFM modes. After doing exhaustive research (pun intended), my final solution to the problem, is to remove the borla system, cut the AFM sections of the OEM exhaust out and mate them to the Borla for re-installation.

xxaarraa

I am curious about MPG after disabling AFM. I have a feeling AFM does not do too much to improve MPG on our cars, but I am not seeing any documentation to prove or disprove my hypothesis...

xp800

My personal experience has been 1-3mpg decrease in steady-state highway mileage with AFM disabled. From an overall MPG decrease in mixed driving is more like 1-1.5mpg.

xxaarraa

I see, thanks for sharing. So Hawk's post on Page 1 claiming MPG increase by disabling AFM seems contrary? I have heard that claim before on another thread as well...

xp800

I can only claim to know my experiences.

Maybe there are some speeds/gears where you're "lugging" in V4 mode and V8 is more efficient. There may also be differences in where these crossover points occur based on aero (base vs. Z51) or LT1/LT4 operational efficiency.

So...for me on my '15 A8 Z51, my mileage increase with AFM in 70-75mph cruising varies between 1-3mpg. Typically 1-2mpg on long trips. I see ~28mpg without AFM and 30-30.5 with it. Around town I don't see much of consequence that I can differentiate from inconsistent driving habits and traffic.

john.wayne

Thanks,

John Wayne

TBBE

Hey guys, I'm new here, & purchased a used 14 3LT with just under 700 miles. & since I purchased have found out that there is no NPP & AFM valves & the sound is not what expected, am looking @ a corsa or borla rear section exhaust? Is it worth it?

TBBE

Sorry meant NO NPP but obviously have the AFM valves*******

EcoBrick Bob

I was told by Hendrick Chevy-Naples that I had a Hard Code showing in my ECM related to the NPP Valve system. I have an "add a fuse" system with a switch in my car, that I can use to effectively disable the fuse and open the NPP at any time. They told me that it is no issue with them, but they had no idea what GM might do to my warranty if they knew about it. I was given the bulletin on this issue.

This code does NOT show up when I check for codes with my MSD Dashhawk.