NPP Always open - questions
 

I'm a new owner, going on 3 weeks in, and I feel a little dumb on this one. I don't consider my exhaust loud by any stretch, but my neighbor, a C7 base owner, rode with me one day and commented that my exhaust sounded much throatier to him at startup compared to his (no NPP). I noticed that the butterflies are always open when the car is off - assumed that is normal. I hadn't noticed that they stay open when the car is started up and idling. I've checked the fuse and it looks fine. I just installed a mild to wild module and noticed that nothing was happening when I pushed the buttons on the remote fob. That's when I went to the back of the car with it idling and noticed the butterflies still open. Are they potentially stuck in the open position? Is this common? Or is it more likely the previous owner did something, besides pulling the fuse, that would keep them open all the time like that, and if so, what?

This is not a huge deal for me as I was already thinking I was cruising around in quiet mode anyway, so if this is as loud as it gets, I'm happy with it. But it renders my little $69 gadget useless.

Might be the previous owner used a bolt or some other method to hold the flaps open. This has been discussed on here before of owners doing this to their npp.

I've read some posts on other forums about faulty solenoids and vacuum lines. Not sure why someone would use any kind of hardware or other method to do this when it's as simple as pulling out a fuse.

If it came with the NPP, check to see if the previous owner pulled a fuse (#5 I think) which would keep the flaps open.

even if you fix the issue where the valves close. they will still be open on startup and close shortly after. that's why it sound throaty when you first start it.

How soon after, though? Pretty much immediately right? In other words, just starting it and letting it sit idling for a minute or two, I should see them closed, or does it take longer? It just doesn't seem like it is in any kind of loud mode when I'm driving around, so I'm wondering if they are actually closing at some point. I've started it with the fuse in and they didn't close after startup. I started it with the fuse out and obviously they didn't close then. And I've started it with the mild to wild wired up and pushing the buttons on the remote does nothing.

The NPP flaps close within a couple seconds of starting the car. They close as soon as it builds the required vacuum.

If you start the car by the time you walk to the back and look in the exhaust they should be closed.

That's what I thought. Must be the solenoid/vacuum thing somewhere. I see nothing holding them open and I can easily push them closed with my hands, though they don't stay closed.

I have a switch to leave them open all the time or function normally, cost about a dollar. The only time I go back to stock functioning is for a long road trip, the NPP can drone a bit at low RPM. Around town or spirited driving I just keep it open.

Found this video, hope it helps.

Yep, I found that too and left a comment - haven't heard back. On his, he found that his fuse got popped by the solenoid grounding out. My fuses aren't popping, so I'm wondering how I can be sure it's the solenoid. I guess it's kind of strange that I want something fixed just so my device that is designed to defeat it can work, because I know I'm just going to leave the exhaust open 99% of the time anyway. I got my window sticker and build sheet from the corvette museum and see that the NPP exhaust is a significantly expensive option, so I feel like I ought to make sure that it works, at least when I want it to. I was also surprised to see that the red calipers option were twice as expensive as the gray wheel option.

I've read a few threads on here that the vacuum line in the engine compartment dries out and cracks and is the source of a leak. It's right in front of the windshield cowl on the drivers side, it's a vac elbow right there and easy to inspect. If you have power and vacuum it should work, so one of those is probably missing.
I love mine open but it is a bit loud so I keep it closed in the mornings in residential areas. Got the evil eye from the old lady next door a couple times :toetap:

If you have the stock NPP setup, it’s probably the solenoid fried. That’s what happened to mine shortly after I installed a mild2wild controller on my car about 5 years ago. I replaced the solenoid and removed the mild2wild controller (bought a Dashlogic, so I didn’t need it anyhow) and I’ve not had a problem since.

Hahaha...

Mine was not working when I got the car, I just didn't know the difference to realize it before I installed the M2W. Anyone have the part number for the solenoid? I've tried to locate the part on rockauto but not having any luck.

Heres a link to an old thread I started back in 2015 when my solenoid went out:

https://www.corvetteforum.com/forums...oid-fried.html

Rockauto doesn’t stock it, unfortunately, but here’s the link to it on Cultrag’s website:

https://www.cultragfactoryparts.com/...valve-25794610

This. +1.

I guess I'm missing something. Are you guys talking about a fuse somewhere other than the one under the interior passenger panel; the same one that the M2W controller fits into? As I stated above, that fuse was good and the fuse in the M2W is good. But I don't see that those fuses are even numbered. So, is this #5 you are referencing located somewhere else?

They are telling you to check the fuse the M2W is plugged into. They apparently didn't read you had already checked the fuse.

I would unplug the M2W and plug a new standard fuse into the slot, start the car and see if the flaps close. That would be simple and eliminate many possibilities for your problem.

If that doesn't work I'd check the vacuum at the solenoid.

I'd solve the problem before introducing the M2W back into the system if it were me.

Good luck.