Chets LS3

so X25 found a solution to retain the AFM valves and cut them out and attach them to the exhaust. Im in the process of doing the same.

During this process I wanted to test the AFM valves (opening and closing "test")

upon startup with the AFM valves attached the valves DO NOT open and close.

I have a video attached below. The AFM valve is open when the car is off. I did not leave the car on long (open headers and its 9pm) I will follow up on some testing tomorrow and try and meter some wires, and see if there is a consistent ohm load between two wires upon startup. Im curious if I can trick the computer. I did this on the onstar box with the C6. car would not start with the box removed. Simply did an ohm test and put a resistor inline and tricked the computer on every startup!

Video added

https://youtu.be/KQ5bny1MV-k




**questions/thoughts.... would the afm module have to be connected to the physical pipe. Im serious if the afm module needs to be connected to the pipe at all, if the test is done internally to make sure the module is hooked up and performs (an internal afm test) because the module does not do a physical test upon startup

X25

Great find! The spring loaded butterfly flaps are on the exhaust, right? If it's not cycling, perhaps it just needs to be clocked for it to be OK. However we couldn't just fix the motor in clocked position, since first time it enters V4 mode, it would fail to move and throw an error code?

Chets LS3

Ok so after messing around and thinking. I can't start the car anymore tonight...its REALLY LOUD at the moment.

If the afm valve which is the same identical valve as the npp valve does not do a physical test and move the butterfly upon startup this leads me to believe:

-The afm valve only sends to the computer that its hooked up and it has not failed.

-also i am thinking the afm valve only turns to open or partially open when commanded by the computer. I do no think it needs to see pressure from the butterfly.

-if the car is in 4 cylinder mode, i think the valve is controlled by rpms and throttle(not pressure on the butterfly)



In short, if this afm valve does not read or monitor pressure from the butterfly, then we can just relocate the black box without the butterfly.

X25

Bu saying pressure from the butterfly, you mean the spring load, right? Afterall, it's the spring that keeps the butterfly in correct orientation, not the exhaust pressure.

What you're saying conflicts with what we've heard in terms of how it works. I'd love to see that you're right, though : )

It's easy to try!

Chets LS3

..correct the spring keeps the valve in the position. but the afm module commands the spring to that position. when released or fully open the spring slowly unwinds and the butterfly is 100% open.

if you physically move the afm valve (on the black box) an imitiate a partial closing (entering 4 cylinder mode) and release the afm valve it slowly goes back to 100% open.


****VIDEO ADDED***

djnice

Maybe the car needs to go to V4 mode and not see the valve stroke and return. Then on next start it triggers the CEL. Somehow it knows when the valves are unhooked or fried.

BaylorCorvette

I do not think so. On the manual C7's they only enter V4 mode in eco mode. When I fried my AFM actuator at the track this year my car was never in eco mode, yet it threw a CEL. Chet and I were discussing this last night and I think we came to the conclusion that the ECU only talks to the "black box" and then in certain conditions the ECU commands the black box to move the butterfly valve. If that is the case then perhaps cutting out the whole section of exhaust with the black box & butter fly valve is not necessary.

AKKutz

If this is the case, you'd think one of the vendors would have come up with a plug in that will trick the ECU. I know LG was talking about it, but haven't come up with one. Hmm, be nice if it were just so simple! I'm ready to eliminate mine completely!

djnice

So for testing you could remove the valve actuator from the valve, but keep it plugged in. Then run the car and if no CEL then you can relocate the actuator. Taking it a step further you could test to see what signal is being returned to the ECU so it knows the valve actuator is alive. Then figure out how to duplicate it.

djnice

Yes, you would think if it was that simple the aftermarket exhaust mfg would have come up with something.

Chets LS3

I will test later today.

djnice

Are you able to drive the car for the test so it can go into V4 mode?

daleong

From the discussion and findings above, my guess is that its the lack of a signal from the AFM actuator back to the ECU is only what triggers the CEL. It doesn't appear this is a signal related to the valve load also.

Tadge alluded to the actuators failing due to the heat damaging the actual electronics inside the black box (maybe melting the board or soldered components?). At that point it probably stops being able to return a signal to ECU that causes the error.

Eager to see what Chet's testing reveals, thanks!!

BaylorCorvette

My thoughts as well.

descartesfool

When my AFM actuators failed, 5 times, there was multiple different conditions in terms of the actuator failures. The first time it happened at the track, car was never in ECO mode of course, and after I turned the car off in the paddock and re-started it, the valves kept banging on and off, making nasty sound while the car was not moving. The CCM module appeared to be trying to check the actuators and since it was getting some kind of failure, it kept trying. I made a video of the sound and played it for the dealer. Sometimes the actuators partially failed, sometimes failed totally. Sometimes with partial failure when in any mode but ECO, there was no noise, but if you put it in ECO while driving home from the track for a test, it made a banging noise. So lots of different failure modes. But a CEL every single time was the common factor.


After the 3rd failure, when I first took the car to the track with a fresh 4th set of actuators, I ran a 30 minute session and drove off the track into the paddock and continued on without turning the car off to go to the gas station. After filling up, I got a CEL as soon as I started the car, and never put the car in ECO mode.


The thing to understand is what happens with failed actuators, with different failure levels, and how that affects the car's CCM checking. But if there are good actuators, then the CCM module might not be activating them at startup. Obviously the secret is to only have functioning actuators connected and moved away from the exhaust heat. If they don't need the return springs, all the better.

Chets LS3

Thanks DF, i just finished a test..on jack stands.

I have started the car on three separate occasions and a 4th occasion about an hour later. I'm currently wrapping them with mcmaster heat material and some heat wrap, I'm then going to attach them to the harness on top of the diff. Im going to face the valve (that opens and closes up towards the car (this piece is not wrapped so it can function when needed)

then I will further test. I'm not sure if I have put this car in eco mode except for the drive home from the corvette museum. haha, so with that being said IF ECO mode is the only thing that possibly sets a CEL then its not a complete failure.

daleong

Good to hear all went well. Were you able to test with just the AFM valve by itself? (i.e. not mounted to the cut out exhaust section). Thanks!

Chets LS3

yes the afm valves are separated from the exhaust and attached by the diff. so far so good!

X25

So the AFM actuators are separated from the butterfly, too, right? No codes? : )

Chets LS3

correct..more to come

updating first post