Functioning NPP for $50
 

After seeing several threads of people trying to hook up their NPP exhaust to a Camaro without that option, I felt that I should make a thread explaining a cheap and easy way to get a fully functioning NPP system without buying an expensive controller. The method I explain below even gives a little more control over the NPP since it will allow you to start the car with the valves closed, unlike the factory system.

Here is basically what we did on my buddy's SS (LS3) when he added the ZL1 exhaust:

We replaced the hard vacuum line shown in this pic behind the throttle body with flexible vacuum hose and a T-fitting. That is not my car in the pic- I just found it on the forum to show which line I was talking about.

http://i86.photobucket.com/albums/k1...ps4d7e8dda.jpg

NOTE: there are also other places to tap into vacuum, like the brake booster, but this is the route we chose for our install.

Here is a pic of the vacuum line replacing the hard line and the t-fitting.

http://i86.photobucket.com/albums/k1...psa30a8220.jpg

http://i86.photobucket.com/albums/k1...ps95c6548a.jpg

Here are the connection points of the soft vacuum line replacing the hard line:

http://i86.photobucket.com/albums/k1...ps3defcff2.jpg

http://i86.photobucket.com/albums/k1...ps95c6548a.jpg

We then ran another section of vacuum line off the T-fitting along the fuel rail into the cabin through the hole in the firewall behind the brake fluid reservoir.

Here is a pic of the routing:

http://i86.photobucket.com/albums/k1...psab215691.jpg

http://i86.photobucket.com/albums/k1...ps86beac7e.jpg

http://i86.photobucket.com/albums/k1...psf83afd86.jpg

We ran the vacuum line in the cabin to a manual vacuum headlight switch from a C3 Corvette like this one:

http://i86.photobucket.com/albums/k1...psgbsjp4ia.jpg

I have found a source for these switches, so PM me for info.

Then we ran another section of vacuum line back out the same hole in the firewall and down under the car following the exhaust pipes all the way back (you will want to find a path away from the heat but following the exhaust route). When we got to the back, we used another T-fitting to split off the vacuum line to run to each of the fittings on the mufflers.

All said and done, we used probably 35 feet of vacuum line, and 2 T-fittings, and the Corvette vacuum switch. We zip tied the vacuum line where we could to secure it properly. If I remember correctly, we did have to use a larger diameter vacuum line to replace the hard line off the throttle body and used a T-fitting with a reducer built in. All pieces were bought from the local auto parts store except the switch, which I already had from restoring my Corvette. Total investment was around $50 (including buying a switch like the one in the link).

Total time to install was about an hour. I had the luxury of using a lift, so it made the job a little easier, but all of this could be done with the car on jack stands.

The switch is mounted under the dash and is completely out of view. The system works exactly like the stock ZL1 exhaust does, but without any electrical components.

I hope this helps. Let me know if you have any other questions.

Thanks for posting. Great info.

What size vacuum line and tee did you use?
Did you consider tapping off the unused port in back of the manifold? (assuming you have one)

So of its run only by vacuum how much
Acceleration makes it open? A little or a lot. ? Seems like the factory limited opening at certain rpms for a reason.
I'm retrofitting soon and will have questions I'm sure.

I believe it was 3/16" tubing to replace the hard line on the intake manifold, and 1/8" ID tubing for the run back to the mufflers. The T-fitting was a reducing fitting so we went from 3/16 to 1/8. This is the kit we picked up with assorted sized fittings.

http://m.autozone.com/autozone-mobil...25ry?id=365546

We did consider tapping the port on the back of the manifold, but I have big hands and my method was easier for me.

The butterfly valves open at more than 50% throttle, which is exactly like my ZL1. I believe they also open at over 3000 or 3500 RPM on the ZL1, but that also equates to increased throttle, so one could make the assumption that 50% throttle or the 3500 RPM threshold are the approximately the same.

I'll put it this way- if the valves are closed and you put your foot in the gas, they open up. When you take your foot off the gas, they close back up. If they are closed and you drive conservatively, they stay closed.

I hope this helps.

And the switch cuts the vaccum so the butterflies are always open, correct?

Yes, you can set it to always open as well. The switch allows total control of the butterfly valves.

So we need to figure out how to open at idle like factory system other than no vacuum.

Yes, if you don't just want to set the switch to open at idle.

It looks like the corvette guys make their quiet mode louder using collars on the vacuum solenoid to hold them slightly open. Hopefully I'll get my npp installed soon.

Ok. I got my mufflers and switch and will be installing soon. http://img.tapatalk.com/d/13/09/12/vy3edury.jpg
http://img.tapatalk.com/d/13/09/12/ehe8ehud.jpg
Ill let you know how it goes.

Installedhttp://img.tapatalk.com/d/13/09/13/ebetu3yq.jpg
Sounds amazing.

Glad to hear this worked out for you!

Thank you. Npp wild isn't too loud, sounds like a beast, snarling and popping. Great exhaust.