Eagle_Gene

I own a 2012 grand sport, my exhaust gets louder when I start up a hill, I can downshift and it will quiet down,,found the solenoid by the pass side tail light,,all looks good there,,has anybody got any ideas?

FX VETTE

Try posting in the C6 section...and welcome to the CF!

DebRedZR1

Moved to C6

C5forGreg

I own a 2012 GS with NPP as well. Maybe I'm not following your question as what you describe sounds like what the NPP is designed to do - RPM's go up, exhaust opens and it gets louder. I would think downshifting, though, would increase the RPM's even more causing the NPP to open up possibly.

FatsWaller

Here is the design: the valves will open at 2,800 rpm above 80% throttle. Between 30% and 80% throttle the exhaust will open during acceleration at and above 3,500 rpm. Mind you, engine load increases going up a hill, so the exhaust will sound louder, especially if you are lugging the engine.

HOXXOH

Correct. Here's the explanation for the OP.
The vacuum that keeps the muffler valves closed is reduced during heavier engine loads. So when you downshift, which increases the engine speed to decrease the lugging load, then the vacuum will increase and close the valves again. This is completely normal operation.

Cockroach

Buy a honda

owc6

Just a little confused by the comment that a 2012 is an "early NPP."

1Hotrodz

Check for a vacuum leak .

Reckedhim

Why do you use two commas?

PAULEB07

87SAM

So old people have a better chance of seeing it

FatsWaller

Two commas can be important. Look at the difference between

Yesterday, I helped my neighbor Jack, off his horse.

and

Yesterday I helped my neighbor Jack off his horse.

jrose7004

I don't quite understand your early NPP reference. I have a 2010 Grand Sport and it has NPP.