Keep NPP closed
Thread Starter
Drifting
Joined: Apr 2008
Posts: 1,343
Likes: 105
From: Mesa AZ
Keep NPP closed
I have a 2008 vert with factory NPP and I was wondering if anybody has a cheat to keep the flaps closed all the time. I have a track day coming up and has a noise ordinance of no more than 94db so I need to keep them closed at all times while on that track. Hopefully someone has done this, pics would help too. Thanks guys.
Le Mans Master
Joined: Jun 2009
Posts: 6,724
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THe washer will be held in place initially by the force of the valve trying to close when the engine's off or limited vaccum, but you must safety wire it into place as the muffler gets hot and expands..which can cause the washer to dislodge.
Be careful you don't pinch a finger when wedging the washer in place when the valves are open...which is their default position when the engine's off.
Thread Starter
Drifting
Joined: Apr 2008
Posts: 1,343
Likes: 105
From: Mesa AZ
Ken...when I ran AMP's sound check late last year, I placed a 1" washer between the actuator arm (at the ball pivot that attaches to the cable)and the metal stop on the NPP housing (which keeps the valves from opening beyond center line), then ran safety wire thru and around the washer to keep it in place.
THe washer will be held in place initially by the force of the valve trying to close when the engine's off or limited vaccum, but you must safety wire it into place as the muffler gets hot and expands..which can cause the washer to dislodge.
Be careful you don't pinch a finger when wedging the washer in place when the valves are open...which is their default position when the engine's off.
THe washer will be held in place initially by the force of the valve trying to close when the engine's off or limited vaccum, but you must safety wire it into place as the muffler gets hot and expands..which can cause the washer to dislodge.
Be careful you don't pinch a finger when wedging the washer in place when the valves are open...which is their default position when the engine's off.
Safety Car
Joined: Feb 2008
Posts: 3,712
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From: TEXOMA
St. Jude Donor '08-'09
Le Mans Master
Joined: Jun 2009
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I didn't take any pics, as I was in a hurry to get to the sound check before it got busy with all the crotch rockets
I think it will make sense to you once you get a look at the actuators.Just make sure when you get the waher wedged in there, safety wire it in there really good. As I was pulling onto the track last year, one of the washers worked it's way loose (guessing as the muffler heated up), which allowed one of the valves to open up.....car blew a 95.6 with one valve open
Tim (SLAMMER) on the other hand, went thru with flying colors....even with Fusions and LT's, as he has the retrofit NPP controller kit on his s/c vert which allows him to electronically keep the valves closed.
Last edited by FNBADAZ06; Mar 15, 2012 at 01:16 PM.
Le Mans Master
Joined: Jun 2009
Posts: 6,724
Likes: 649
Hhhhhmmmm.....wonder if this would work. You need to have the valves closed completely for a 15 minute session. Have you ever tried using the check valve method you recommend ?
Last edited by FNBADAZ06; Mar 15, 2012 at 01:14 PM.
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Thread Starter
Drifting
Joined: Apr 2008
Posts: 1,343
Likes: 105
From: Mesa AZ
O.D.
I didn't take any pics, as I was in a hurry to get to the sound check before it got busy with all the crotch rockets I think it will make sense to you once you get a look at the actuators.
Just make sure when you get the waher wedged in there, safety wire it in there really good. As I was pulling onto the track last year, one of the washers worked it's way loose (guessing as the muffler heated up), which allowed one of the valves to open up.....car blew a 95.6 with one valve open
Tim (SLAMMER) on the other hand, went thru with flying colors....even with Fusions and LT's, as he has the retrofit NPP controller kit on his s/c vert which allows him to electronically keep the valves closed.
I didn't take any pics, as I was in a hurry to get to the sound check before it got busy with all the crotch rockets
I think it will make sense to you once you get a look at the actuators.Just make sure when you get the waher wedged in there, safety wire it in there really good. As I was pulling onto the track last year, one of the washers worked it's way loose (guessing as the muffler heated up), which allowed one of the valves to open up.....car blew a 95.6 with one valve open
Tim (SLAMMER) on the other hand, went thru with flying colors....even with Fusions and LT's, as he has the retrofit NPP controller kit on his s/c vert which allows him to electronically keep the valves closed.
Last edited by ktoonsez; Mar 15, 2012 at 01:57 PM.
Le Mans Master
Joined: Jun 2009
Posts: 6,724
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You'll see what I'm talking about when you get to the mufflers on your car.
Here's a crude image with pointers showing the area I'm talking about.
Melting Slicks
Joined: Dec 2006
Posts: 2,694
Likes: 106
It's very simple to keep them electrically closed all the time with a manual NPP switch. Just search for 'Old School NPP switch' for wiring instructions (basically you feed the NPP circuit from the seat heater one). I wired them that way, but with a very nice and super thin rocker switch under the dash.
However, I don't know if that would work for you since prolonged WOT operation might deplete the vacuum reservoir before you lift the throttle, and give it time to recover. But if track is technical, it could work very well. And you'd have to make no other changes, plus now you have full control of your valves. Good luck, and hope this helps.
However, I don't know if that would work for you since prolonged WOT operation might deplete the vacuum reservoir before you lift the throttle, and give it time to recover. But if track is technical, it could work very well. And you'd have to make no other changes, plus now you have full control of your valves. Good luck, and hope this helps.
Thread Starter
Drifting
Joined: Apr 2008
Posts: 1,343
Likes: 105
From: Mesa AZ
Thanks for all the reply's guys. Looks like I am going to try the washer idea. I found a square piece of flat stock 1" wide so hopefully that will work as the washers here just a touch too wide at 1-1/8th.
Le Mans Master
Joined: Jun 2009
Posts: 6,724
Likes: 649
It's very simple to keep them electrically closed all the time with a manual NPP switch. Just search for 'Old School NPP switch' for wiring instructions (basically you feed the NPP circuit from the seat heater one). I wired them that way, but with a very nice and super thin rocker switch under the dash.
However, I don't know if that would work for you since prolonged WOT operation might deplete the vacuum reservoir before you lift the throttle, and give it time to recover. But if track is technical, it could work very well. And you'd have to make no other changes, plus now you have full control of your valves. Good luck, and hope this helps.
However, I don't know if that would work for you since prolonged WOT operation might deplete the vacuum reservoir before you lift the throttle, and give it time to recover. But if track is technical, it could work very well. And you'd have to make no other changes, plus now you have full control of your valves. Good luck, and hope this helps.
This particular track in AZ just reopened after an 8 year court battle with the city, which originally gave it's blessing and issued permits, regarding noise. The track owner has placed a sound meter at the straight away to monitor the noise, but the city has/does place several sound meters just outside of the fence. If they get a reading above 99 db, they shut down the event (for everyone, no refunds) and fine the track owner.
That's why I went with physically forcing the valves closed.....I don't want to be the one who f's it up for all the other paying participants and get's the track closed.
Sucky deal, but it is what it is....unfortunetly.
Le Mans Master
Joined: Jun 2009
Posts: 6,724
Likes: 649
You'll see in his pic that he is restricting the valves in how much they are opening when vacuum is lost instead of holding them shut completely...but the premise is the same.
http://forums.corvetteforum.com/1578279839-post10.html
Tech Contributor
Joined: Oct 2008
Posts: 1,378
Likes: 11
From: St Louis MO
Another owner went a different route, but achieved the same result, using a clamp, some washers, and a wingnut.
You'll see in his pic that he is restricting the valves in how much they are opening when vacuum is lost instead of holding them shut completely...but the premise is the same.
http://forums.corvetteforum.com/1578279839-post10.html
You'll see in his pic that he is restricting the valves in how much they are opening when vacuum is lost instead of holding them shut completely...but the premise is the same.
http://forums.corvetteforum.com/1578279839-post10.html
I'm pretty sure with just a check valve the gates will open anyway just due to the exhaust flow pushing the valves open.
Team Owner
Joined: Sep 2000
Posts: 24,903
Likes: 2,619
From: Far NW 'burbs of Chicago
St. Jude Donor '13
It's very simple to keep them electrically closed all the time with a manual NPP switch. Just search for 'Old School NPP switch' for wiring instructions (basically you feed the NPP circuit from the seat heater one). I wired them that way, but with a very nice and super thin rocker switch under the dash.
However, I don't know if that would work for you since prolonged WOT operation might deplete the vacuum reservoir before you lift the throttle, and give it time to recover. But if track is technical, it could work very well. And you'd have to make no other changes, plus now you have full control of your valves. Good luck, and hope this helps.
However, I don't know if that would work for you since prolonged WOT operation might deplete the vacuum reservoir before you lift the throttle, and give it time to recover. But if track is technical, it could work very well. And you'd have to make no other changes, plus now you have full control of your valves. Good luck, and hope this helps.
Perhaps the terminology has changed?
Thread Starter
Drifting
Joined: Apr 2008
Posts: 1,343
Likes: 105
From: Mesa AZ
So I got home last night and found a little easier way to do it, I am sure others have figured this out or it just might be my year car or the age of it but thought I would share. Turns out the ball attached at the end of the arm comes off the swing blade really easily with a flat head screw driver so you dont' have to fight the force of actuator making it much easier. Here is some pics, I haven't safety wired it yet as I am going to get some tonight, but here it is:
Last edited by ktoonsez; Mar 16, 2012 at 10:19 AM.
Team Owner
Joined: Sep 1999
Posts: 41,732
Likes: 1,717
From: Springfield MO
You can take a piece of wire and(when the engine is running and the vacuum is holding the valves in the closed position) and loop around the vacuum pot and the spherical ball ends to hold the valve closed when there is no vacuum(on the track) to hold the valves closed). At the end of the day, remove the wires.
Le Mans Master
Joined: Jun 2009
Posts: 6,724
Likes: 649
So I got home last night and found a little easier way to do it, I am sure others have figured this out or it just might be my year car or the age of it but thought I would share. Turns out the ball attached at the end of the arm comes off the swing blade really easily with a flat head screw driver so you dont' have to fight the force of actuator making it much easier. Here is some pics, I haven't safety wired it yet as I am going to get some tonight, but here it is:
