[vetteflier]

Watched a few Youtube vids about older cars and found what I wanted. The module taken off the housing--plastic module attaches to metal exhaust housing to control flaps, which was identical to the one on my M4C. Three 10mm bolts hold it to the housing. Remove it, and you will see a slot. Turn the slot to the fully opened position--I used a needle nosed pliers, it turns easily. If you feel resistance, turn it the other direction--I forget if it was clockwise or counter clockwise. This completely opens the flaps. You need to unplug the connection on the right side to get to one of the bolts. They're all clear on the left. Then, unplug the left lead, electric tape over the connection opening, and cable tie it to the suspension--or anywhere else you'd like. Valves are open and will stay that way.

Haven't taken it out to check the new sound yet, but expect it will be a significant improvement, as the flap was very rarely fully opened, except at full throttle advance. Freer flowing exhaust is always good, and will add a few horses at every rpm where the flaps weren't fully opened. Any mod to the exhaust in front of the valve would be limited to only fully gain when they were fully opened from a sound perspective--and the sound is the one area I wanted to improve. There are $200-300 devices on sale to do the same thing that I did for free. Only problem I had was only being able to use one hand to do it all. If you can raise the rear by 6" or so, would be much easier.

[BIGW0RM]

I suspect you will get a CEL doing that.

[OneCleanBMW]

Originally Posted by BIGW0RM

I suspect you will get a CEL doing that.

Why would the CEL turn on?

[///AVM]

Originally Posted by vetteflier

Watched a few Youtube vids about older cars and found what I wanted. The module taken off the housing--plastic module attaches to metal exhaust housing to control flaps, which was identical to the one on my M4C. Three 10mm bolts hold it to the housing. Remove it, and you will see a slot. Turn the slot to the fully opened position--I used a needle nosed pliers, it turns easily. If you feel resistance, turn it the other direction--I forget if it was clockwise or counter clockwise. This completely opens the flaps. You need to unplug the connection on the right side to get to one of the bolts. They're all clear on the left. Then, unplug the left lead, electric tape over the connection opening, and cable tie it to the suspension--or anywhere else you'd like. Valves are open and will stay that way.

Haven't taken it out to check the new sound yet, but expect it will be a significant improvement, as the flap was very rarely fully opened, except at full throttle advance. Freer flowing exhaust is always good, and will add a few horses at every rpm where the flaps weren't fully opened. Any mod to the exhaust in front of the valve would be limited to only fully gain when they were fully opened from a sound perspective--and the sound is the one area I wanted to improve. There are $200-300 devices on sale to do the same thing that I did for free. Only problem I had was only being able to use one hand to do it all. If you can raise the rear by 6" or so, would be much easier.

vetteflier

Thank you for the writeup.

I am bit confused on why all of these steps are required?

If the valves are open, then you pull the plug . . . wouldn't that simply leave the valves open constantly?

Perhaps it is no easy task to actually get the valves fully open before pulling the plug unless approached in the manner you describe?

Namely, seems full valve opening is only achieved in Sport Plus with aggressive throttle. By the time you reach as stop, the valves might be closed again?

Any insight?

Also, I might have missed somewhere, but did your approach produce the desired results? Valves fully open all of the time?

I have always liked the idea of purchasing a valve controller system, however, they all seem to come with wiring/mounts/etc that I simply do not want to deal with . . . and do not believe having the valves fully open all of the time would be a problem for me. If so, I would simply plug back in.

///AVM

LBbluem2 I am pinging you on this post because I believe you too have tinkered with this topic

[jonahk]

Following this thread. I thought one of the unique things about the G8x was the exhaust flap was variable instead of a binary on/off.

Curious as to how just opening the flap 100% of the time affects engine warm up or performance in general and doesn't throw a code of some kind.

[TrentMeister]

Originally Posted by ///AVM

vetteflier

Thank you for the writeup.

I am bit confused on why all of these steps are required?

If the valves are open, then you pull the plug . . . wouldn't that simply leave the valves open constantly?

Perhaps it is no easy task to actually get the valves fully open before pulling the plug unless approached in the manner you describe?

Namely, seems full valve opening is only achieved in Sport Plus with aggressive throttle. By the time you reach as stop, the valves might be closed again?

Any insight?

I have always liked the idea of purchasing a valve controller system, however, they all seem to come with wiring/mounts/etc that I simply do not want to deal with . . . and do not believe having the valves fully open all of the time would be a problem for me. If so, I would simply plug back in.

///AVM

LBbluem2 I am pinging you on this post because I believe you too have tinkered with this topic

So I tried to unplug them during a cold start in S+ and it seemed like they found their way to being shut again.

I was kind of suspicious that maybe there was a return spring inside of the actuators that would default the valves back to a closed state when I unplugged them.

I'm trying this out today thanks op for the r&d on this solution 👍🏼

[///AVM]

LB

I've been under my car this morning contemplating.

Seems the difference between your approach snd OP's is he removed the harness and manually opened valves. Conversely, you relied on S+ setting which, per my prior post does not assure full valve opening unless aggressive throttle . . . and not sure they remain open by the time you come to a stop?

What I hope OP can confirm is that his approach worked as desired. Valves fully open all of the time.

///AVM

[TrentMeister]

Originally Posted by ///AVM

LB

I've been under my car this morning contemplating.

Seems the difference between your approach snd OP's is he removed the harness and manually opened valves. Conversely, you relied on S+ setting which, per my prior post does not assure full valve opening unless aggressive throttle . . . and not sure they remain open by the time you come to a stop?

What I hope OP can confirm is that his approach worked as desired. Valves fully open all of the time.

///AVM

Ahh I see,
I'll go do it right now-go for a drive-and report back

[TrentMeister]

Ok 2 problems with this method.

Valves rattle at certain times.

Full throttle slams the valves closed.

We need a valve controler.
///AVM

[vetteflier]

No CEL as there would be no reason for one. Power still goes to the module plug and the ECM assumes the purely mechanical connection to be working. As to simply unplugging with the valves open--there is no way to ensure they are completely open when you do it. I've tried revving in sports plus--don't stay open. The whole purpose of this is noise reduction, period--just like on my Vette's NPP, and that is precisely what I didn't want. No "rattle" on start up that I heard. Continuous exhaust flow keeps them in the upper position. No way they can 'flap around.' The purpose of the module is to hold them 'closed,' as exhaust would push them open. Engine warmup has no bearing on exhaust flow, and as I said, any time you can increase exhaust flow at any point in the rev range, you increase power. Back pressure is not an issue, as 2 of the 4 pipes remain flowing into the muffler 100%.
As to my test drive, valves stayed fully opened at all times. Louder and deeper exhaust note while cruising, significant increase with part throttle acceleration, and best of all: burble on over run. Also significant increase on rev matching downshifts, but no real burble. However, exhausts can take well over a 1000 miles to 'break in,' increasing and deepening tone thereafter, so I'm hoping for that. All in all, 100% satisfied with a 20 minute job that improved the one knock I had on the car. I'm spoiled after driving Corvettes with free flowing exhausts for 15 years and didn't expect the TT 3 liter to sound like a 6.2 liter NA V8, but a step in the right direction. And it cost me exactly the same as pulling the fuse in my '18 Vette to keep the valves open all the time: $0.

[TrentMeister]

Originally Posted by vetteflier

No CEL as there would be no reason for one. Power still goes to the module plug and the ECM assumes the purely mechanical connection to be working. As to simply unplugging with the valves open--there is no way to ensure they are completely open when you do it. I've tried revving in sports plus--don't stay open. The whole purpose of this is noise reduction, period--just like on my Vette's NPP, and that is precisely what I didn't want. No "rattle" on start up that I heard. Continuous exhaust flow keeps them in the upper position. No way they can 'flap around.' The purpose of the module is to hold them 'closed,' as exhaust would push them open. Engine warmup has no bearing on exhaust flow, and as I said, any time you can increase exhaust flow at any point in the rev range, you increase power. Back pressure is not an issue, as 2 of the 4 pipes remain flowing into the muffler 100%.
As to my test drive, valves stayed fully opened at all times. Louder and deeper exhaust note while cruising, significant increase with part throttle acceleration, and best of all: burble on over run. Also significant increase on rev matching downshifts, but no real burble. However, exhausts can take well over a 1000 miles to 'break in,' increasing and deepening tone thereafter, so I'm hoping for that. All in all, 100% satisfied with a 20 minute job that improved the one knock I had on the car. I'm spoiled after driving Corvettes with free flowing exhausts for 15 years and didn't expect the TT 3 liter to sound like a 6.2 liter NA V8, but a step in the right direction. And it cost me exactly the same as pulling the fuse in my '18 Vette to keep the valves open all the time: $0.

Wait... how did you get the valve controller to fit back onto the opened valve?

It took me 20min to get them realigned to go back on.

A actually left the whole servo off of the car for my test with the valves 100% open

[///AVM]

Vette

I just did it, kind of. Very easy, BUT one major problem. I turned the diaphragm to open valve. Visually confirmed open valve.

However, the big problem is the motor (in removed cover) is no longer oriented to fit onto turned diaphragm. In other words, the diaphragm turned (valve open), but the motor is still in closed orientation.

I could not manually turn it to match orientation of open diaphragm. Thus, I could not put the cover back on because it requires matching orientation of diaphragm.

///AVM

[vetteflier]

Originally Posted by LBbluem2

Ok 2 problems with this method.

Valves rattle at certain times.

Full throttle slams the valves closed.

We need a valve controler.
///AVM

I remote started the cold car right behind the exhausts. No rattle of any kind. We do hear things differently, and I'm not doubting what you said, but non-issue for me. As to reinstalling the module with power removed and valve open position, you can in fact do it. Simply start the car--the slotted shaft on the module will be full closed position. Get the car to open the valves--the shaft will rotate while you watch, then quickly disconnect the plug. You can then put it back on the housing and the shaft will keep the valves firmly in the open position. Would need to do it twice, of course, but if the 'rattle' bothers you, I would do this.

[TrentMeister]

Originally Posted by vetteflier

I remote started the cold car right behind the exhausts. No rattle of any kind. We do hear things differently, and I'm not doubting what you said, but non-issue for me. As to reinstalling the module with power removed and valve open position, you can in fact do it. Simply start the car--the slotted shaft on the module will be full closed position. Get the car to open the valves--the shaft will rotate while you watch, then quickly disconnect the plug. You can then put it back on the housing and the shaft will keep the valves firmly in the open position. Would need to do it twice, of course, but if the 'rattle' bothers you, I would do this.

Ahhh I see, the rattle was a product of me leaving the controller completely off

[vetteflier]

I don't understand "full throttle slams the valves closed." There is no mechanical way this could happen. The valves rotate on the vertical axis upwards to horizontal. The lower part is slightly in the exhaust stream, so flow would push it outward=open, if anything. For them to close, you would have to have much greater flow at the much smaller inward side of the valve.

[TrentMeister]

Originally Posted by vetteflier

I don't understand "full throttle slams the valves closed." There is no mechanical way this could happen. The valves rotate on the vertical axis upwards to horizontal. The lower part is slightly in the exhaust stream, so flow would push it outward=open, if anything. For them to close, you would have to have much greater flow at the much smaller inward side of the valve.

All I know is I manually pulled both servos from the car. left then off. and opened the valves to wide open.

The car sounded great while I was warming it up once the cold start stopped rattling the valves.

Around town it was deep and nice.

Once warm I put it in s+ and layed on it suddenly it had this strange howl to it that I had never heard and was much quieter than I'm used to at full throttle.

I took it out of sport and back to efficient and the car was dead silent as if the valves had shut themselves.

Again I completely removed the servos for my test.

[///AVM]

Originally Posted by vetteflier

As to reinstalling the module with power removed and valve open position, you can in fact do it. Simply start the car--the slotted shaft on the module will be full closed position. Get the car to open the valves--the shaft will rotate while you watch, then quickly disconnect the plug. You can then put it back on the housing and the shaft will keep the valves firmly in the open position.

vetteflier

How do I 'get the car to open the valves'?

Of course, the black plastic housing will be off and the valves already open - because I manually turned diaphragm to open them.

So, when you say 'get the car to open the valves,' I assume you mean valve motor in the housing will rotate to open?

If so, I still do not understand how I will get the car to do that??

///AVM

[///AVM]

Originally Posted by LBbluem2

All I know is I manually pulled both servos from the car. left then off. and opened the valves to wide open.

The car sounded great while I was warming it up once the cold start stopped rattling the valves.

Around town it was deep and nice.

Once warm I put it in s+ and layed on it suddenly it had this strange howl to it that I had never heard and was much quieter than I'm used to at full throttle.

I took it out of sport and back to efficient and the car was dead silent as if the valves had shut themselves.

Again I completely removed the servos for my test.

LBbluem2

I do not know, but I suspect that since you left the plastic housing off the forces at play while driving caused the valves to close?

Partly because the valves are on a swivel, and they simply swiveled shut.

Partly because the plastic housing motor that couples with the diaphragm was not replaced; that coupling, in whatever position you have the valve when unplugged will secure the valve into position.

I also suspect your 'rattling' is related to fact you did not put housing back on.

This brings me back to my problem, which is I do not know how to get the housing motor to match the diaphragm, allowing me to put it back on in open position (and unplugged, of course). vetteflier will hopefully clarify.


///AVM

[vetteflier]

Couple of things. To LB--were the valves open or closed when you got home? From what you said, they should have been closed. Having flown fighters, the dihedral effect would mitigate against exhaust flow closing the valves, as I said it would need much lower angle of attack at the back valve edge than the front (opened) valve which is in the airflow. Exhaust flow is linear, although turbulent. I see no way this could occur. And it certainly didn't when I test drove yesterday. But, in an abundance of caution, if you will--you can wire the valve to hold it open. Several ways to do it, from a paperclip on the right side to steel wire on the left. Simply hook the end of the "bar" in the housing that turns you want to remain closed to one of the bolt holes or tie off on the side of the housing. There is then no way it will close against that restraint.
AVM--plug the electrical connector into the module. Have someone rev the car until you see the shaft rotate to the full open position. Unplug immediately. You can then fit the module to the housing and the slot on the shaft will fit into the housing. As I said, you need to do it for each side--and a helper. Do it quick, as the valves close suddenly, it seems, and for reasons I don't comprehend.

[///AVM]

Originally Posted by vetteflier

AVM--plug the electrical connector into the module. Have someone rev the car until you see the shaft rotate to the full open position. Unplug immediately. You can then fit the module to the housing and the slot on the shaft will fit into the housing. As I said, you need to do it for each side--and a helper. Do it quick, as the valves close suddenly, it seems, and for reasons I don't comprehend.

vetteflier

Getting closer . . . (1) Wake car up by hitting ignition with foot off brake. (2) Engine set to SPort+. (3) Start engine. (4) Rev engine. (5) Can see shaft rotate. (6) Pull plug before it returns.

The PROBLEM is the shaft never seems to rotate far enough (e.g., it never rotates to valve fully open) which, obviously, is where I want it and manually turned valve diaphragm.

Any thoughts on why the shaft will not turn to FULLY OPEN to match the diaphragm fully open position??

///AVM

[vetteflier]

The variability of the computer controlled flaps is a pita. One suggestion would be to put a screwdriver in the slot on the shaft and as gently as possible turn it to full open. I have no idea of how the servo works, but it can't be very strong as moving the flap takes little effort--why you can manually turn it so easily, and I doubt it would break it. It's only important if you plan on someday returning to variable flap control, obviously. I can't see why you would, as the sound will definitely be better--with a slight power gain throughout the rev range. Personally, I like my approach the best. Can be returned to stock in 10 minutes, and if you want to be absolutely certain the flap will remain fully open, just paperclip it or wire it. Wiring is easiest if you can get the car in the air, as the left assembly is hard to get at. Also, even if there was a "rattle," which again I didn't hear, it would eliminate that as the flap would be tightened.

[///AVM]

Originally Posted by vetteflier

Personally, I like my approach the best. Can be returned to stock in 10 minutes, and if you want to be absolutely certain the flap will remain fully open, just paperclip it or wire it. Wiring is easiest if you can get the car in the air, as the left assembly is hard to get at. Also, even if there was a "rattle," which again I didn't hear, it would eliminate that as the flap would be tightened.

Thank you Vette

So you are saying you did not put plastic housing back on?

You just secured diaphragm in place and left plastic housing off?

I'm more inclined to your screwdriver suggestion, and will give it a shot.

///AVM