tslsa28

Hello, I am going to a track day with a 84 db sound limit. Can the factory NPP on a stock 2013 LS3 be forced closed? I don't like the idea of mechanically locking it unless that is only choice. Or maybe the 84 db isn't a problem with the NPP working? Thanks.

jft69z

Do you have a dashlogic unit? If so, you can leave it in 'quiet' mode and the valves won't open at all, even when it reaches the 3500 rpm point. It can be cycled through the 3 modes with the mirror selector switch.

tslsa28

I don't have a dashlogic. Maybe I'll get one. Is it an aftermarket item or stock?

jesse82nc

Dashlogic has a quiet mode, I've used that a few times when I was driving around an area and didn't want to attract a lot of attention.

https://www.corvetteforum.com/forums...-corvette.html

tslsa28

Thanks. I'll look into that. You mentioned the mirror selector switch, is that in conjunction with the dashlogic? Is there any other way to control the NPP without the dashlogic?

jesse82nc

You toggle the mirror selector switch in conjunction with the Dashlogic to control the NPP settings. The center position is stock, left is open always I think and right is closed always if I remember correctly.

You use the door lock switch to page through the gauges on the HUD and DIC.

If you pull the NPP fuse it will stay open all the time. I don't think there's any other way to make it stay closed all the time, at least not easily.

tslsa28

Thanks. I'm looking at their website right now.

Mike's LS3

I have dashlogic, but does the Mild to Wild switch allow to keep the valves closed at all times?

jft69z

No, MTW just takes the place of the factory fuse, so to speak. It will still work the valves at the factory triggered rpm.

realcanuk

The M2W NPP in a box allows you to keep it open or closed.

jft69z

Must be different than the regular M2W with just the remotes?

realcanuk

Dunno. It's what I have. Comes with 2 remotes. Just google it and see what it is exactly.

Mike's LS3

So when you say closed meaning factory default or closed and will not open at all?

realcanuk

Closed always.

jft69z

Looks like it's for cars that didn't come factory with NPP system. You need to provide your own NPP mufflers.

http://nakidparts.com/id78.html

The M2W unit that is used with factory NPP mufflers won't keep them closed all the time.

jft69z

Also Mike,

If you have both DL & M2W, the M2W will over ride the DL if you force the valves open with it. The Dashlogic won't be able to control the valves, because the M2W basically opened the circuit (like pulling the fuse).

If you want to use the DL to get all 3 modes of exhaust options, the M2W switch will need to be set accordingly (mild).

jrose7004

I have a mild to wild switch on mine.

gsflyer2011

84 db should not be a problem with NPP open. I do not think you have to do anything.

Dano523

Walk in the park.


Remove the inner tail light and look straight down in the fender cover void.



Remove the thumb bolt to remove the cover to the NPP solenoid.


Remove the two air lines to the each side of the Npp solenoid, then using the OEM 90* barb connector, connect both lines to each other directly.

Hence you want to connect the end of hose 18 Barb fitting directly to the hose 28, bypassing solenoid 27.


Hence the car sends power to the NPP solenoid to open it up to allow a vacuum to pass through to to close the muffler gates, then kill the power to the Npp solenoid to allow the gates to open up. With a by pass of the solenoid, the gates will stay closed.
Note, there is a vacuum reserve ball in play, and will hold enough vacuum to keep the muffler gates closed when the intake manifold goes to Zero vacuum pressure for the few seconds that you are standing on the throttle WOT it/ to create the zero intake vacuum conditions for a few seconds.

StKnoWhere

You can Clamp them closed, here's something I MacGyver'd, you can adjust them all the way closed.

https://www.corvetteforum.com/forums...post1578279839

A stainless steel tywrap might work also.