X25

[ONLY APPLIES TO NON-Z06 cars since Z06 does not come with this actuator]

[WARNING: It involves cutting pipes in your car. This is not for someone who would like to keep everything stock on his car. It is your car, modify it at your own risk ]

As many of you know, AFM actuators are poorly designed, and their tiny motors melt after a prolonged exposure to high temps that occur at the track or during aggressive driving. So far, GM has been replacing them when they fail, but having to go to the dealer to get them replaced after every few track days is NOT really a solution. GM has no answer so far for this issue, and "ASK TADGE" section's question for this weekend is this very question.

I decided to eliminate the issue before having to visit the dealer, so came up with a solution:

What you need:

• Exhaust heat wrap (I used DEI heat wrap).
• Mask (to not inhale the heat wrap's fiberglass).
• Metal zip-ties.
• Tail-pipe expander.
• A good muffler shop to work with.

Steps:

• Remove the rear fascia per instructions here.
• Remove the exhaust mufflers.
• Take the exhaust mufflers to a reputable exhaust shop.

The actuators right behind the big mufflers are the AFM actuators that actually melt.


IMPORTANT: Have the exhaust shop put the mufflers onto a rig before removing the actuator. This way, the exhaust piece cannot be clocked or angled wrong during the operation. We simply need to get the actuator cut out from the welding points it already has. Since the actuator tests its flaps during the car start, you need to keep the actuator connected to its flaps, which is why we need to get that piece of piping cut out.

• Wrap the mufflers.

Wrap the exhaust pipe with heat wrap. This is crucial, since this will further cut the heat transfer to actuator and the diff, and it will also prevent rattling noises when the actautor's piece of piping touches the exhaust.


I put a bit of a wrap material under the actuator for extra insulation on my first actuator. On my second one, I just wrapped it even more, so didn't need it : )

• Re-installing the mufflers.

Use the tail pipe expander to enlarge the slip-on portion of the exhaust for easy re-install of the mufflers.
The actuator is more likely to rotate over the pipe and come close to exhaust on the passenger side, since the diff doesn't have lines on that side, so it has more space to play. I zip-tied the actuator's harness to keep it from getting too close to the exhaust.


Pic of the passenger side muffler. Install the mufflers slowly, making sure actuators are not stuck as you move the piping into its place. Before you replace the bolts that hold the muffler by the side and middle mounts, rotate the actuators towards the diff and connect them. When you tighten the muffler bolts, the mufflers will self-align and raise quite a bit, making the actuators stuck between the insulated pocket room above the diff housing. This actually will keep the whole actuator assembly in place, which is why we never needed to strictly fix the actuators on the pipe.

• DONE!

Remarks / concerns:

• No error lights: I have started up the car, and there are no check engine lights or any such issues!
• V4 mode: I am yet to try the car on V4 mode, but it's supposedly sound worse without the actuators.
• Track test: I am yet to test this set-up at the track. I am trying to make it to the Sunday (July 10th) open track day and stress-test it. We'll see if it holds up, but even if it will eventually not, it would take time since people had issues only after a handful of track days.
• Target audience: This is a mod very useful for frequent track days attendees or racers, but it's probably not necessary for street use.
• Improvements: I think I would wrap the actuators even more, if I were to do it again. You might also find a different solution, like a different location, thought the limited harness length forces us on the location. Perhaps someone could come up with an extension cable. Better yet, someone could come up with a simple simulator circuit, which would be great! Even better, GM could decide that it's OK to turn off AFM actuators at the dealers for those who don't want it, so we don't need to care about it anymore, or come up with a solution of their own

raylo

What we need is for some clever vendor to develop an actuator simulator plug like the ones for CAGS so you could lose the actuators completely.

BaylorCorvette

Good work, glad there is an option since I've already melted them once and no doubt will continue to do so..

X25

Thank you; indeed this is an alternative. If GM does not come up with a better solution, this might become a good way of solving it.

Chets LS3

X25. If your under there and have a multimeter. Could you turn the ignition on and see what the ohm load is at each pin.

X25

Well, I'll hopefully not get down there for a long time, but you should also keep in mind that there's a test cycle that's run when you start up the car, which should also be simulated besides the static resistance of pins.

Chets LS3

Indeed. Is the test upon complete crank. Or upon ignition turn on would be the question

X25

If I were the engineer, I'd do it after successful engine start, but I really don't know. These are very easy to observe and measure, though, if anyone already has the bumper removed. Anyone?

Cromagnum

Will spirited driving on hot summer days lead to this? Sounds like a major pain in the ***.

X25

I'd highly doubt it. Looks like for most, even with track day duty, it took a few track days for it to happen.

Chets LS3

its really random, I have not popped an afm valve yet and I have about 10-15 track days I run on slicks and usually very aggressive. In comparison I claimed a TT2 record and rebroke it twice at time trials in 88-90* weather. Yet Ive seen people melt the afm valves and never been on the track.

kevincol

What year is your C7? Z51 or Z06?

Chets LS3

2016 z51

kevincol

Then I will stop worrying about my track day on 8/11...

X25

BaylorCorvette also has a '16 Z51, and he melted AFM actuators after a handful of track days. YMMV.

0Anthony @ LGMotorsports

Working on it...

No ETA yet

daleong

Can I be first in line to buy one??

daleong

Yes BaylorCorvette did melt his, but during a session in which his trans temp got to 306, which is way in the red. I think if you watch your trans temps and dont let it get too high you probably will be ok.

I mean I'm sure GM did do a lot of testing of the Z51 when it launched and if it was happening a lot they would have solved it years ago.

Hopefully, LG can find a plug and play solution also. If not X25's engineering is a great option too..

BaylorCorvette

Chet is a faster driver than me too and I've never been on slicks so I'd say his car takes a bit more punishment. Frankly I'm surprised he isn't going through AFM sensors like crazy. Not sure if Chet did any track days in mid to high 90 degree temps either.

Also as daleong pointed out, my trans temp got to right over 300*F no other track event did it get over like 275*F. Perhaps that has some part to play, I can't say for sure. At the end of the day it is a very real problem for 2014-2016 C7 non Z06s. Fingers crossed that GM comes up with a backwards compatible solution or else I'm going to be hacking my system like X25..

Chets LS3

^^^ that's a lot of quotes so I'll start fresh. I suppose I've been lucky. I had 2 90+* days and that's it. It's too hot to run right now for me and the car. We live in the Deep South. Humidity is 90+ and temps are 95-100* it's brutal. So I'm waiting for a little bit.

Also I'm waiting on a used z06 cords exhaust and will do what x25 did and delete them so to speak.