Manual tranny with NPP, I found an oddity, does yours do this?
 

I noticed that if you are cruising along maybe about 30-40 mph in sport exhaust mode, and you step on the clutch and coast, the valves in the exhaust close and go to tour mode.

Let the clutch out, and the valves open back up like they should be while in sport.

Weird.

Does yours do this?

Before anyone asks, the reason I found this out, I pass by a friend's house a couple times a day, and if he's outside I goose the throttle and give him a little exhaust sound, lol (it works great with my Foxbody, my C7, not so much)

He's a car guy too, he's got a Chevy Truck restomod.

It's kind of a cooler way of honking and waving! :D

Can't confirm this as I have an auto tranny, but interested in knowing whether that is the way it happens with the M7.

I have been reading up on the npp and it seems it closes at certain rpms and if you press the clutch in the rpms drop so would make sense it closes.

:iagree:

I have an M7 and they definitely close somewhere around 2200 2300 rpm no matter the mode you are in. Don’t quote me on rpm but it’s in that neighborhood I believe.

You can always try the pulling the fuse thing. Keeps it open at all times I think.

I never "coast" w/the clutch depressed at any speed in my Z51 7MT (or in any other MT vehicle for that matter) but I pulled the fuse for the NPP a while ago and, as far as I know, the pipes are always open.

Sounds like you have Rev Match turned on.

It's probably because engagement of the clutch pedal results in the engine RPMs going to idle, is why the exhaust becomes quiet.

Try slapping it into neutral

Is rev match on or off?

I think this makes the most sense.

rev match was off, I was able to replicate it a couple times.

It really doesn’t matter much, I just found it an odd quirk, and wondered if anyone else noticed it.

thanks everyone!

There is a "hitch" in RPMs where the M7 quiets down: https://www.corvetteforum.com/forums...ck-result.html

Are you in 3rd gear? The valves are basically always open if you're above 1500rpm in sport or track but 3rd gear is tuned for noise regulations so if you get on it in 3rd it closes the valves between like 1500-3000rpm to comply with this standard.

yes I’m pretty sure I was. I think this explains it, thanks!

If you go into the infotainment system and set sound management to "track", the valves will stay open.

Track closes the valves during low rpm highway cruising, and they are closed at lower RPM. The only way to keep the valves open all the time is to pull the applicable fuse.

:iagree:

Nope.....this is an old wives tail.

Has anyone tried to use a Mild to Wild to keep the NPP open on a C7 M7? Please do not get off track here; I am NOT speaking of the valves that work in 4 cyl mode.

Nope. I set mine using the infotainment system (not using the dial on the console) several months ago and the NPP valves are still in "track" mode (i.e., not in stealth, tour, or sport mode).