I have 2009 C6. My NPP Exhaust is not working properly. The butterfly valve that open and close are not doing anything at all... It stays open all the time. While the car is off, I understand that it should stay open but when I started the car it stays open. I check the fuse by passenger and it is on there and in perfect shape.

I understand that many people remove the fuse in order to have it open all the time. I just want it to be operational. Should I take it to the dealership?

I got the car last week. It is GM CERTIFIED with warranty. The car has just over 4000 miles.

 

The vacuum line may be unhooked and/or plugged or damaged.

Some info and links in here to start checking:

http://forums.corvetteforum.com/c6-t...eshooting.html

 

I will go and buy another fuse to be sure. I think I will just take it to the service department and have them fix it.

Maybe the previous owner just put the NPP exhaust on and the vacuum line was never hook up in the first place. However on top of the mufflers, where the valves open and close, is something suppose to be hook up to it?

 

Well, just the obvious vacuum canisters, linkage and vacuum line to each side.

 

If you don't know whether the car actually has the NPP or not, check the label behind the glove box door...look for code "NPP"

 

I just checked it.. I have no Vacuum line to each side at all.. SAD PANDA.

 

Checking the Glove Box now. NPP!

 

My car has B&B Fusion exhaust, same thing as NPP. Mine did not work when I bought the car. After 7 hours of checking, I found the electrical switch located behind the passenger side inboard tail light was bad. Pretty easy to replace. If you want to know how to do it, pm me.

 

appears someone removed them...?

 

I am not sure, but the it's not there. Will take it to the dealership and have them deal with it.

 

^ s/b an easy fix...

 

Well, I was going to take it to the dealership, but decided to check glove box one more time outside garage and it didn't say NPP. I think the previous owner put it on. However since it came with the car when I bought it would GM hook it up?

Also if I let it be the valve stays open would I be losing back pressure or low end toque? And do I now have 436 HP and 428 tq?
Ty

 

If the dealer won't hook it up, just manually close them and see how you like it. On mine, I'm so rarely above 3,500 RPM for them to open I doubt I would miss it. Sounds great on startup though.

 

I only close mine (via M2W) at highway speeds (bit of drone). I love the exhaust sound when the valves are open
at all other speeds/times, especially the gurgles, pops, etc. on deceleration !

 

When the valves are closed the car sounds like an electric razor.

 

Since your car was not factory-equipped with the NPP exhaust, they can't just "hook it up."

That is, I'm guessing you don't have all the parts to make it fully functional: Or maybe the previous owner installed a fully functional NPP system... look for a control module in your passenger-side rear storage compartment.

Also, look at your fuse panel in the passenger footwell (under the carpet). Compare it with the pictures on pg 6 in the installation instructions:
I'll bet the previous owner liked the NPP mufflers open all the time, so didn't bother installing vacuum lines & a module to control the system.

 

CO is correct.

 

c'mon folks...the rules about non supporting vendor links are easy to follow...

 

Seems like the previous owner just put the exhaust on it. I like the sound, I just don't want to lose low end back pressure or toque if any?

So with the NPP exhaust, I now have 436hp and 428tq?

 

If you leave the valves in the open position .......... The engine has always produced those numbers. The base, non NPP axle back muffler system, chokes things down. That's why the Corvette w/ NPP can advertise higher numbers. Simply said, when the valves open, the system is more free flowing, thus the higher hp/torque rating. You'd need a dynamometer to really see the difference. What you need to do is buy the M2W accuator kit from one of the forum vendors that will make the NPP functional.