Functioning NPP for $50

[WIKID SS]

Originally Posted by 4RSS FED

Having just researched all of this, I might be able to provide some info.

The V8's use 2.5" pipe. The 2012 ZL-1 exhaust part # is 22874269 which changed to this part # 22990282.
The V8 NPP exhaust part # is 22756148. There is also a V6 NPP exhaust (additional mid section resonator and pipe size difference).
The NPP diffuser part # is 22815277

From what I was able to find out, there is a slight difference in the angle of the tips of the ZL-1 and the price tag. I have not seen the NPP and ZL-1 exhaust side by side, but I am guessing the tip difference is to match the rear fascias. I have the 269 pipes on my car. They mount up and look good on my 2012 SS with the NPP diffuser. As far as muffler internals I do not believe there is a difference but don't know for sure.

If you convert back to your stock manifolds and cats it will work fine and it will be quieter than with the long tubes and high flow cats. I have the SLP s/c running through the factory SS manifolds and cats. I have not had any problems and I am using the SLP supplied tune. If you are already tuned with the headers/cats, you might want to try it that way first?

Thanks for the great info. The part number you gave me for NPP diffuser, is that from the 1LE or ZL1? I think the 1LE will fit better on 2010 SS. Again thank you for your help!!

[4RSS FED]

1LE/NPP rear fascia.

Direct replacement.

[WIKID SS]

Originally Posted by 4RSS FED

1LE/NPP rear fascia.

Direct replacement.

Great, Thanks again.

[bjones71087]

I've been thinking about adding npp to my car for a little while, but here is my thought for an easy install. Take a 12v vacuum pump, like this one: https://www.sparkfun.com/products/10398 .

With that, you would be able to control by switch. It would have no on or off effect by engine load, but work more like electric cutouts. Quiet when you want, loud when you want.

Anyone tried anything similar? Not sure how well it would open and close..

[jravenfan]

Originally Posted by bjones71087

I've been thinking about adding npp to my car for a little while, but here is my thought for an easy install. Take a 12v vacuum pump, like this one: https://www.sparkfun.com/products/10398 .

With that, you would be able to control by switch. It would have no on or off effect by engine load, but work more like electric cutouts. Quiet when you want, loud when you want.

Anyone tried anything similar? Not sure how well it would open and close..

Did you get a chance to try this, was wondering how it worked.

[darkcrave]

While idling at a stop, wouldn't just revving the engine cause the valves open as well?

Originally Posted by 4RSS FED

.

Function is dependent on engine load and not rpm.

Adding the mechanical vacuum switch just allows you to shut off the vacuum being sent to the muffler valves and 1. have them open all of the time or 2. force them open when they would normally be closed and you want a little more noise, for example idling at a stoplight. I think the function is similar to the M2W which is a remote activated electrical switch used to cut the vacuum instead of the plunger type mechanical switch used here. Maybe someone who has the M2W setup can comment on its function.

Hope this helps.

http://youtu.be/nxr-Nou58Ug

[4RSS FED]

Yes if you stabbed the throttle hard enough they would open for a brief moment as the engine vacuum drops but would close back down as you back out of the throttle before you tach out. There is a little bit of lag in the system as the valves move and how much movement you get between revs might not be real noticeable.

Hope that answers the question. Maybe this video will show the relationship better than i can explain it. Toward the end there is a slow rev to 3000 rpm with high vacuum (no load) versus the other quick revs (load).

https://youtu.be/RRXKdBR78Vw


So to recap with this setup: (non-factory NPP) in normal operation with vacuum applied to the system, there is variable positioning of the exhaust valves when the vacuum level is between 10 - 0 inches. Starting to open at 10, half way open around 5, full open at 0. At idle you are around 16-17 inches of vacuum and under deceleration 24-26" to give you some reference values. So if you are revving at idle, you could only give a little rev and hit 7", a little more and hit 3" with the valves moving the appropriate amount. But you are only there briefly as you let off the gas for the next rev. If you want to make more noise, install the vacuum switch and break the circuit so the valves are open.

If you do not have a vacuum gauge in the car, all of these numbers are probably nonsensical but hopefully it explains the relationship on how it functions.

[Surfrman]

ok, I want it always in wild mode, im have and ss with out npp option, just buy a pair of zl1 mufflers, so I just need to install them with out any vacuum hoses and those thinks, just leave it like that?

Thanks

[blackoutVIII]

Mine sounds like the video all the time!!!! I had the GMP off road axle backs installed before the car was taken home. Now I want it to have a louder rumble. Long tubes and removing the resonators will be my noise making combo. of course power too!!

[guns2go]

I have installed long tubes and cat deletes, the car sounds incredible, but loud. I have the mild to wild so I can have the mufflers always open, what I would like now it to have an option for closed at idle...anyone worked that out yet? Just need to sneak out of my neighborhood on the early mornings.

[xc_SS/RS]

Finally found some mufflers locally off of a ZL1. Trying to work a deal currently and get rid of my current mufflers.

[Demon War Horse]

Any pics on routing of the vacuum lines from the muffler valves under the car? I am looking at doing this as well. I am good with the routing under the hood from the pics on page 1, but how about the connections to the mufflers for routing to not get the lines too hot to melt?

Thanks!

[Deke736]

Originally Posted by Demon War Horse

Any pics on routing of the vacuum lines from the muffler valves under the car? I am looking at doing this as well. I am good with the routing under the hood from the pics on page 1, but how about the connections to the mufflers for routing to not get the lines too hot to melt?

Thanks!

Sorry, no pics specifically of the hose routing to the back. Follow the exhaust and you'll find points to tie to. The connections to the valve on the muffler is far enough away to not melt. As long as you route the hose in a path that won't get pinched, you'll find plenty of options to route it unseen and away from exhaust heat.

[Shawno72]

Great write up. I am purchasing a zl1 exhaust in a few days fr my Lfx. Can't wait to hear it