mountainears

For me I just wanted to have it quiet in some situations and open all the time in others. I wanted that easily done and quick. So I just went with the mild 2wild setup and use the visor buttons. I have the exhaust set to Stealth in all settings and I just turn it on or off with the visor switch. No in between if there even is something.

Only way to really know I guess is if someone puts a camera on it. If they do, I would suggest also running the PDR at the same time to capture that video and telemetry, the tow videos could then be synchronized and the truth would be told.

When I get my car back I might see if I have a camera I can use to do that.

LT1 Z51

There 100% is a sound difference at idle. Between Stealth/Tour and Sport/Track, at higher RPM's Sport still is louder than Tour but Track gets louder. Has to happen somehow.

Also just because diagnostically they can be commanded full open or full closed doesn't mean that those are the only two options.

Diagnostics are just that, tests, not functionality. That command more than likely is attempting to test the entire range of actuation.

Foosh

Jerry,

I have a M2W installed, and you are correct. M2W "on" is the same as OEM with fuse in. M2W "off" is the same as pulling the fuse.

With the fuse installed and in Track mode (M2W "on"), there is no drone when cruising at highway speeds below 2K rpm (6th and 7th gear in an M7). With M2W "off" (same as fuse pulled) there is a noticeable drone.

Clearly the NPP valves are closing in Track mode with the fuse in at low rpms.

JerryU

Thanks, so in fact the Service Manual is in error! Perhaps they had planned to have what everyone wanted to be the case, i.e. when in Track the Butterflies would always be open!

Foosh

I think it was just a bad manual writer, but the NPP valves are open in Track mode "most of the time." When the valves are closed during low rpm highway cruising, it is beneficial to eliminate a drone that is not at all pleasing

btorlv

I push the 2 tabs but cant get the top or handles to budge? Don't want to be dumb, but what is the trick? I also read fuse 41 is for a 2014.

joemessman

Try to be a little more forceful with it. You wont break it. It is flexible plastic. And by the way. Be sure to look at the inside of the lid when you remove it. The diagram is there for all the fuses.

Foosh

Forgot about the handles. Those are to remove the entire fuse box.

You don't need to touch the handles to remove the fuse box lid. Only the front two tabs on the lid need to be released.

Yes, the NPP fuse for '14 models is #41.

bbdmac

Does anyone know the type of fuse used for #42? I lost mine after pulling it and I've tried micro2 size APT and APR and neither one is an exact fit. Or if anyone knows the GM part number. I ordered some from GM for my 2016 Z06 and they were wrong too! Slightly large with different contact posts. Thanks.

The GM part I ordered was part number 88861352 and it's definitely not correct.

joemessman

Here are two photos. One standing on end view and the other a flat view.

dndrsn

The NPP fuse is a Micro 2 fuse. 20A Micro size. 2 legs.

Look inside the lid of the fuse box. Number 65 thru 75 are spare fuses
number 69 on my car is a 20A fuse.

bbdmac

Thanks everyone for confirming. GM must have sent me the wrong parts because what I received was supposed to be correct but it clearly doesn't fit. I do have spares in those locations but since I lost the original I wanted to get some additional spare parts. Looks like you can't trust GM to ship the correct parts......

dndrsn

Red Mist Rulz

It's possible things have changed since the '15 model year, but try this. Drive at about 50 mph with the exhaust in Tour, then switch to Sport. On my '15, the exhaust gets louder. Then switch to Track. It gets louder still. That pretty much proves that in Sport at that speed it's neither fully open nor fully closed.

In the LOOONG thread about NPP, there's a post from someone who spoke with Tadge about this. He asked Tadge why the valves aren't open all the time in track mode, and Tadge replied "because then it wouldn't be legal."

Here it is. Lot's of very detailed info in posts 248 through 258 here: https://www.corvetteforum.com/forums...post1589742949

LT1 Z51

Yep this was my logic. At certain speeds there are three or four distinct sounds (Silent is quieter than Touring sometimes). Therefore you had to have "multiple settings" to get different noise.

The only way around this I could see is for example you have different settings for left and right valves, but I think that only gets you three settings (both open, one open, both closed). Need to find out if that could be managed (pressure differential would be an issue), but even that goes out the window once you get to four distinct sounds!