Bill Dearborn

Sorry, I thought somebody said it wouldn't switch in Sport Mode. It seems like there is a lot of mixing of terms. If the transmission needs to be in manual to keep the engine from switching to V4 mode then the trial should be done that. Set engine sound management to Track, Select Transmission Manual mode and drive around like somebody with an M7 and see if the valves close. If you can verify they close then maybe there is a difference between M7s and A8s. I doubt it since the FSM would have indicated that but maybe it was overlooked.

I can try and use the PDR to record the sound made while driving my car in Eco and then Tour on a slight upgrade at 50 mph in cruise in 6th gear.

Bill

Thomasmoto

My car isn't stock, 2016 Z06. When we changed the cam we lost the CD ability, but even when sound management set to track my valves will close at lower speeds or lower power levels. So I have pulled the fuse. It's the only way to guarantee the valves remain open 100% of the time, which is how I like it.

Thomasmoto

Bill, I can tell you this since my first C7 Z06 was a 2015 Z06 M7.There is a big difference in how the car lets you use the accel pedal much more than the A8's do. The A8's won't rev up high like the M7's will. And it's a big enough difference to be able to tell just by driving. So having a difference in how the NPP works wouldn't surprise me one bit. But I know for 100% certain that pulling the fuse/MTW switch, is the only way my car will keep the valves open 100% of the time.

Warp Factor

Yup, both with what happens between the two kinds of "track" modes (one on the rotary dial on the center console, and the other on the touch screen), and the differences between the M7 and A8. The "sound management" function on the touch screen changes nothing but the flow path through the mufflers.

Bill Dearborn

You may have lost the AFM activity with the engine but I have been reading in the Service Manual and although it isn't clearly stated it looks like the Chassis Control Module (not the ECM) initiates the start and stop of V4 operation by sending signals to the ECM. I was also reading how the Range AFM Module works and they indicate the module disrupts the signal to the ECM telling it to initiate V4 mode. The Chassis Control Module is connected to the ECM through a data bus plus directly controls the muffler valves and it is likely that it gives a command to both the engine and the mufflers but only the mufflers receive it. The only way to know is with a completely stock A8. Supposedly the A8 doesn't implement V4 when it is set in manual mode. Set Engine Sound Management into Track Mode, Run manual shift mode with ride control set in Tour and see if the exhaust changes. Then do the same thing again with the transmission in auto shift mode in Tour and see if the exhaust noise changes with V4 operation. That can be done by setting the instrument cluster display to info and whatever screen shows V4/V8 operation in the center of the tach/speedo.

Bill

chromeXskull

Hi, new Corvette owner and have read mixed things about fuse 42 and 87 on the C7s. I just purchased a 2019 Grand Sport and I’d like to be sure my valves are open. I drive in sport mode but have the sound setting on the display set to track mode.

My understanding is pulling this fuse will guarantee the valves stay open. I have yet to see if it should be pulled when the car is off, while running or after the car has warmed up then off and also should the actual drive mode be in track mode when you pull the fuse? Does any of this matter to guarantee the valves are open when the fuse is pulled and stay that way?

thanks for any help

Bill Dearborn

If you have an M7 and want the valves open all the time (except in ECO Drive Mode) to the Settings Menu on the screen and select Engine Sound Management and then select Track. That permanently opens the valves with an M7 car. If you want to use Eco Driving Mode the valves will always close when the engine switches to V4 mode.

If you have an A8 and want the valves open while you are driving then do the same procedure as above for the M7 to set exhaust to Track (not in Track Driving Mode) then manually shift the transmission and the exhaust valves will never close. Put the transmission in Auto Mode and the valves will close every time the chassis controller thinks the car is in V4 mode. You really don't want them open in V4 mode anyways as the sound wouldn't be all that great. The A8 makes it more difficult to hear the valves open all the time because whenever the transmission is auto mode Eco mode will operate no matter what driving mode the console selector has selected.

Simple but confusing because the word mode changes its meaning depending on what section of the car you are talking about. Drive Mode, Exhaust Mode, Transmission Mode, Engine Mode, etc.

Bill

Zjoe6

Track mode still depends on engine rpm. If you’re cruising down the highway and your rpms drop below 1700 they will close. At least mine do. 2019 GS M7.

Bill Dearborn

Have you looked at them while driving to see them close? Put your car in Eco Mode and drive around town or on the highway at near constant rpm with the rpms between 1000 and 1500 rpm you will hear the valves open and close as the car switches between V4 and V8 mode. Just because the exhaust is quieter during part throttle low rpm operation doesn't mean the valves are closed. You can look at the open valves while the car is parked with the engine idling and not hear a lot of noise.

The following two pages are from the 2015 Factory Service Manual describing how the exhaust system works. Item 4 tells you how the Track Mode setting works and it clearly states the valves are open all of the time in Track Mode. The See Note Above reference addresses the AFM issue. People can argue about this as much as they want but since the factory doesn't change how the exhaust works during vehicle build all it takes is one vehicle to verify this operation and I did that with my car. This is how it works and all the others do as well. The paragraph below point 4 states the exhaust valves are open in all Driving Modes. Reading further about how Cylinder Deactivation changes the exhaust valves you will see where it states when AFM is active that over rides everything and the valves are closed. Very clear, right from GM.




Bill

MontanaBob

After having spent a ton of time reading posts and creating responses on this NPP valve closure issue, I decided to buy a "Wild to Mild" remote switching device to install in the fuse panel, which cuts electrical power to the the NPP valve actuators at the fuse panel. Granted, this is only my car, a bone-stock 2018 Z06/Z07 3LZ A8 coupe, but the exhaust note, (sound level) does not change one iota (decibel) regardless of whether the center stack display exhaust setting is set to "Track" mode or left to change itself when the mode setting is in "Touring" with the "Mild to Wild" switch set to "Off" which cuts the power to the NPP actuators.

I am sure that there will be those that will still not believe it, but in my car, the NPP valves do not close, regardless of speed, transmission gear, engine RPM, mode or whatever, as long as the "Engine Sound Management" setting in the center-stack display is set to remain in "Track". To put it another way, the "Mile to Wild" switch kills the power to the NPP valve actuators, hence they are totally inoperable. Don't believe me, install a "Mild to Wild" switching device and prove me wrong. Don't think that you can though.

Montana Bob

Bill Dearborn

I agree that killing the power to the valves will leave them open just the same way pulling the fuse does. I also agree once the power is killed by pulling the fuse or using a power switch like mild to wild the engine sound management settings don't do anything. No power, no work.

However, what happens when you have the mild to wild set to mild and you have engine sound management set to Track?

Bill

MontanaBob

Bill,

Just tried it, although, I can't drive the car due to the foot of snow that we have, so, the car is tucked away in the garage. I merely started the engine and tried it whilst the engine was at idle.

Anyway, with "Mild to Wild" set to mild and "Engine Sound Management" set to "Track", the sound level remains the same. Only when the "Engine Sound Management" is set to "Stealth" can the NPP valves be forced to stay open with the "Mild to Wild" switching device. This proves to me that the NPP valves are spring loaded in an open position. Killing power through the use of a "Mild to Wild" switch, or by pulling the fuse, permits the springs to hold the NPP valves open. Reapplying electrical power to the NPP actuator overcomes the springs, closing the valves.

This switch becomes handy when traveling and you want to listen to the radio, or chat with your wife, Then one only has to push one button on the "Mild to Wild" device to close the NPP valves, rather then mucking about in the center stack whilst moving at speed on a freeway. Other than that, the "Mild to Wild" switch accomplishes nothing that one can't do in in the center-stack in "Engine Sound Management".

I think that what people are missing is the the fact that our cars have variable valve timing which is going to affect the exhaust note. If not, in addition to a louder exhaust note, the idle would be a "rumpity-rump" as we had in days of old when we all had aggressive cams with a lot of overlap. Don't you agree?

Montana Bob

PS: Discovered a trick by accident last summer. By flooring the accelerator and, of course, holding the brake, the engine will not start, but will merely turn over, permitting oil to circulate and come up to pressure before engine start. Merely releasing the accelerator, while still holding the brake pedal, permits the engine to start instantly. Handy for those of us who have our cars parked for the winter season. I've not seen this trick mentioned anywhere, not even in the Owners Manual. Have you seen this anywhere?

Zjoe6

I obviously can't look at my valves while driving but all I can say is that I can cruise a long stretch of road in some higher gear, then use the accelerator to go just above and just below around 1700 rpms, and there is an abrupt change is sound level. If it's not the valves then something else is doing it. I'm not imagining it. But I get everything you're saying and I have read the same pages in the manual.