opua

I listened to all three clips and still not sure what NPP does.
http://forums.corvetteforum.com/show....php?t=1747836

If I understand NPP sound correctly, NPP gives you a quieter engine sound below 3,000 rpm. At 3,000 rpm and up, something opens up and gives you a louder sound.

So, a stock exhaust will be louder below 3,000 rpm, but quieter above 3,000 rpm relative to NPP.

Is this right?

cerino2000

there are a total of four pipes coming out of the mufflers. For each muffler, the inside pipe is almost of a straight thru design, the outside like a normal muffler. With NPP, the engine opens up a butterfly above generally 3000 RPM which is blocking the inside pipe thus giving you a wide open sound.

Here's a vid that hows the NPP in action as well as a product called Mild-2-Wild. Listen to the exhaust in mild mode. When in mild mode, this is the computer in stock form controlling the exhaust.

Right Click Here and Save Target As

AORoads

Cerino's correct. Let me add some corrections. First, the valve-actuated pipes open at 3500 rpm. Second, a stock exhaust will be quieter all the way, below or above 3500 rpm. That means the NPP exhaust, imo, is very slightly louder than stock even WITH the two pipes in the closed position.

And yes, above 3500 rpm or when the valves open in the two pipes, stock exhaust will be much, much quieter.

Even tho you didn't ask, the biggest difference is that with this exhaust, you can almost never activate the "loud" exhaust if you choose NOT to. And you can, if you want, cruise on the highway with almost no loud exhaust since the valves aren't opened at cruising rpms (usually below 1800 rpm for 55-75 mph in top gear).

cerino2000

No, really, it opens at 3000 if you are at 60% throttle (or some other threshhold, can't remember). 3500 was the myth but after I got mine, I tested it. It's 3000.

04BlackCoupe

I agree, mine opens up at 3,000 rpm not 3,500rpm when under 60% or more throttle.

AORoads

I'll take your word for it, cerino.....until tomorrow. I think mine, I can hear it starting to open just above 3K rpm, but it really doesn't get to full open until 3500 rpm. I could be wrong. And on full acceleration, it does seem to be 3500.

I guess I'll just have to test it tomorrow.

Corellian Vette

Anyone notice if you are behind the car while its idling it sounds like a exhaust leak. The valves dont seal up 100% and IMO dont sound to good.

Modshack

Opening RPM's depends on % of thottle opening...

///M3C6

Also does this have to already be on the car or can they install it if you want?

FLZ_Boy

To have a factory operating NPP, the Vette has to come with this option from the factory.

You can still have a NPP exhaust bolted up on a non-NPP vette, but the valves will remain open 100% of the time.

talon90

Thanks for postng my slide Modshack, you saved me the troube. I'll just add these.

cerino2000

I actually looked for this and didn't notice that it sounded like a leak.

Jedsvet

I don't hear anything that sounds leaky ...

I do like the moment when you start the motor and the valves give you a nice short RUMPF sound, looks like they are open right when it starts.

LittleJake

The NPP gives me a hard on, I absolutly love it and am so glad I got it as an option. Once I installed the Mild2Wild I loved it even more.

Man it sounds great when open and quiet when closed. I love it!

Did I say I love it already? If not I love it!

Jet Stream

NPP is very little bang for the buck for what you get. You gain 6HP and a mechanical muffler that will be service prone IMO. When you figure in the cost above the stock system the NPP option is almost 2 grand. I think the aftermarket offers better sounding less restrictive systems below 3000rpm for the buck.

cerino2000

Not sure where you figure the 2K but regardless, the absolute best part of the NPP is the ability to have an excellent sounding exhaust with no drone...or if you want drone, just pull the fuse.

Cost wise, it is a no brainer. I went through 3 different aftermarket exhausts and every single one of them went to the way side (and at a cost since they were now used) over drone. Withe the NPP, you have the best of both worlds. No drone when you don't want it, and it sounds kick *** when you do want it. AND..it's a factory piece so it is covered under warranty. By far my favorite option on this car.

bill_5r

I agree that there are better sounding aftermarket systems but the NPP has the ability to be quiet when you want. That is a nice option to have at 4:30am when I leave for work.

Bill

Patiently waiting for my '08 TPW 10-22

opua

Cerino, thanks for the video of mild-2-wild. That was great comparison. Way way better sounding than the link I provided above, also the sound from different perspective.

AORoads

I missed that chart! Thanks, Mod.

Hmm, so maybe it does open at 3K rpm and more depending on throttle position. Good. I still like it!!!

///M3C6

Also does this have to already be on the car or can they install it if you want?