Theta

See above for tuning question. Other relocation question would be solved by the two options listed above involving the actual butterfly valve units.

NoOne

And they say reading is overrated

So for my next crazy idea.....install cut outs before the valves assuming they are under the car and it can fit.

Cut outs open, no real heat past the cut out to affect the valve.

FYI do not install the cut outs so that they point directly at the rear spring. I did that on my C5 and melted the rear spring after about 15 hard laps on track.

Funny thing was after the rear spring broke and the back end collapsed I was much faster the next few laps until I pulled in.

Theta

I could see dumps being a band-aid, but his best bet for now is to keep as close to stock as possible to continue to have this looked at. I feel bad, because if I remember correctly, he has a pile of mods waiting to go on.

Also, dumps on a track could cause sound check issues, especially since I've had to engineer a system to keep the NPP closed during Track mode due to track sound regulations.

FYREANT

Speaking of which, how's that coming along? Haven't seen any updates this week?

NoOne

Little lift past the pickup mic

That is what we used to do, at the direction of the track owner.

Or the older style cut outs I had to hold the button down until they opened fully. Maybe cracking them 50 percent reduces the temp enough.

descartesfool

A little lift is not going to work for tracks where they check you in the paddock with a mic 15 feet behind the car and have you snap the throttle up the rev range. They are not as dumb as they used to be back in the day. Noise ordinances are much more powerful than tracks in many localities. Residents pay a ton more real estate taxes than the track does, and they vote. Track owners might have a couple of votes at best, if they actually live there. I never thought a quiet car slowed me down on track. NPP on the C7 only makes 5 HP so it's pointless for speed, yet it makes a ton more noise.

descartesfool

Just got some really good news from my dealer on the AFM actuator issue. He got a communication that GM has authorized that they replace my 2014 muffler exhaust sections with 2015 equivalent sections, as those have what GM has called "insulated inlet heads" where the AFM actuators mount. Parts are ordered and will be installing shortly.

thebishman

Great news. Fingers crossed.

Bish

Iceman09

Well, this is the first time I've heard of someone else experiencing this issue. After my first track day (1 hr of track time in 20 min sessions) my CEL came on for AFM valve(s). I took it to the dealer and they said it will require replacement of the valve(s). Unfortunately, mine is a 2015 M7 Z51, pretty much identical to yours except I presume it has the "insulated inlet heads" you speak of. I guess only time will tell, I will be taking it back in after I return home in a month or so.

567Chev

That's disheartening. Hopefully you find out your car actually did not have the insulated head even though it's a '15.

I'd like to remove them as an exhaust upgrade. But if it can't be tuned out or faked out, the answer seems to be somehow bolting unused AFMs to the bottom of the car.

Has anyone done this and have pictures on how they did it?

c6switchblade

I have the same issue with the CEL to an extent, look through HP tuners a few times and there is no matching diagnostic code to modify. I am going to have to learn to live with it for the time being. I also thought about extending the wires and cutting the actuators off and mounting the partial pipes in the fuse box area in the trunk.

descartesfool

Info I got from GM via my dealer is that the replacement muffler/exhausts for my non-NPP 2014 Z51 that comes with the "insulated inlets" have the following part #'s, which I looked up on a GM parts site:

23290447, $626.71 list
23290448, $626.71 list

I looked up part numbers for a 2015 C7 non-NPP muffler and found these:

20968758 replaced by 23231400, $615.17 list
20968762 replaced by 23231401, $615.17 list

So the top set of part #'s must be a new part as they did not come up when checking for a 2015 exhaust, where the other numbers above did. They did come up as valid part numbers when I just checked them per their part number, with that slightly higher list price, so looks like they are indeed new parts.


If you are having failures with your AFM actuators, ask your dealer for a warranty upgrade to these parts (sorry don't have the numbers for NPP equipped Z51).

sigelitest

So is the exhaust different or the actuators?

descartesfool

Those part numbers are for the exhaust/muffler sections. Haven't heard of a change in the actuator part number.

Theta

Thanks for keeping us up-to-date on this.

I know it's a pain in the butt to ask you to get pictures of any of the changes, but it would certainly help me (and I'm sure others) doing development on/with the actuators.

I'm thinking they've added a heat shield/de-coupler between the butterfly valve female and male interlock on the actuator. Dollars to doughnuts they've kept the actuators the same, so it has to be with the butterflies, themselves.

I'm VERY curious to see if it's only on the AFM butterflies or on both those and the NPP butterflies.

sigelitest

Any gm Tecs on here able to answer what they changed. .

Theta

Sorry, but you won't have much luck there with the internal regulations.

sigelitest

Is there 2 different npp exhausts or is this problem only with the non npp exhaust? If there is 2 different npp setups anyone have the gm part number of the upgraded npp?

Theta

Updated part numbers are listed in post #32 by descartesfool.

The new numbers will simply supersede the previous numbers, as I'm sure all NPP exhausts now have these changes (however small/large) applied. There will be a cutoff date / changeover that most likely will only be identifiable from looking at the mechanical change (if visible).

Issue at hand here is/was dealing with high temperatures of the AFM butterflies, in turn causing the AFM valves to fail prematurely under heavy load situations.

Zajac

I have been following this thread because I am expecting to track my 2015 base C7 this July. The daytime temperatures at Miller Motorsports track near Salt Lake City will be about 100 F. The HPDE Time/Trial sessions will be 25 minutes long. I am debating what to do....

1. Many other guys have thus far tracked their C7s but not many seem to note or mention their AFM failures on the track in the forums. Regardless, "Descartesfool" is batting 100% with 3 failures at the track. I would expect similar failures when I track my C7.

I am not adding anything new in my comments below but just re-stating the problem and what I will do in the short term.

2. AFM failures at the track are caused by high exhaust temps at the AFM installation location . The GM "real" fix for tracked C7s is still not available yet. Non-tracked C7s do not have an AFM failure problem.

3. The AFMs are present in the exhaust over the axle as a high tech answer for changing exhaust tone in the V4 mode only. Sheesh! I don't think I care about exhaust tone in V4 mode unless there is cabin drone.

4. The AFMs are checked on every startup and failures result in CELs.

5. Short term "bandaid" is exhaust wrap around the over axle exhaust and also around the AFM module. However, excessive heat may still transfer from exhaust to the AFM module via the butterfly shaft.

6. Longer term "bandaid" is relocating the two AFMs with actuators/wiring in the engine compartment somewhere. What a kludge! The car is now no longer "stock" with no AFMs/etc in the axle over exhaust.

7. Wait for the long term fix from GM. But how long? GM knows that only a small percentage of C7s guys track their car and have this problem. So in reality, regardless of track preparations done as directed in the owner's manual, the C7 is still not track ready. Rats!