Troubleshooting NPP Exhaust - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

rmyers · 07-03-2023, 10:35 AM

Does anyone know how much vacuum is required to close the actuators on 5th gen NPP exhaust?

The exhaust actuators on my 2012 Z are open all the time and do not close. The fuse is in place and is working.

I ran a vacuum hose from the connection of each NPP actuator to the inside of my car and placed a gauge on it so I could see if vacuum was being supplied while driving.

I tested each side separately, and each time the vacuum would range from 0 to -75 kpa.

So I know I have vacuum at each connection to the actuators, but they will not close. The actuators are NOT stuck, and can be closed by manually pressing the linkage in towards the canister.

Does anyone know what minimum vacuum required for normal operation should be?

The car was modified several years ago, and did receive a larger camshaft, heads, and other mods. About 660 hp at the wheels. But my recollection is that they still worked after the mods were made 11 years ago.

Any advice or technical information would be much appreciated.

Ron

LevonH · 07-03-2023, 10:43 PM

Try a handheld vacuum pump on the actuator and see what that does. This Thread may help with some diagnostics.
https://www.camaro5.com/forums/showt...&highlight=NPP

FasNuf · 07-03-2023, 11:26 PM

I made a switch that has 3 modes. Auto (factory setting) Open, and closed. When in the closed position at morning start, it takes about 1 second for the valves to close and stay closed at idle so I don't think a ton of vacuum is needed. If you're interested how to connect an ON OFF ON type switch, watch my video below.

Sorry had to edit and verify myself. If your fuel system has had the FPCM removed, this will disable the NPP., this is also known as K38 Chassis Control Module.
Timestamp 2:32 in the video is the schmatic with the switch shown.
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https://youtu.be/R1WfpAotXIY
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rmyers · 07-05-2023, 10:18 AM

Thank you for my sharing. I was aware of the 3 mode mod, but not your video. This will be extremely helpful. 1st step for me though is making them work as intended.

BTW, what manual were you referring to in the video?

FasNuf · 07-05-2023, 10:46 AM

BTW, what manual were you referring to in the video?[/QUOTE]

It's the 2014 Factory Service Manual. I think they're available online in digital form but I don't know.

rmyers · 07-06-2023, 09:26 AM

I am pretty sure I solved the problem. It was so simple, its kind of embarrassing. Turned out to be a vacuum leak at the actuators. Now on to the 3-mode switch modification.

07-03-2023, 10:35 AM	#1
rmyers Drives: Both American Made Join Date: Feb 2008 Location: Texas Posts: 781	Troubleshooting NPP Exhaust Does anyone know how much vacuum is required to close the actuators on 5th gen NPP exhaust? The exhaust actuators on my 2012 Z are open all the time and do not close. The fuse is in place and is working. I ran a vacuum hose from the connection of each NPP actuator to the inside of my car and placed a gauge on it so I could see if vacuum was being supplied while driving. I tested each side separately, and each time the vacuum would range from 0 to -75 kpa. So I know I have vacuum at each connection to the actuators, but they will not close. The actuators are NOT stuck, and can be closed by manually pressing the linkage in towards the canister. Does anyone know what minimum vacuum required for normal operation should be? The car was modified several years ago, and did receive a larger camshaft, heads, and other mods. About 660 hp at the wheels. But my recollection is that they still worked after the mods were made 11 years ago. Any advice or technical information would be much appreciated. Ron __________________ 2012 ZL1 #213 M6 Black on Black 2013 ZL1 #2638 Convertible Auto 2010 Chevrolet Suburban 2011 GMC Seirra HD Denali

07-03-2023, 10:43 PM	#2
LevonH Chevy Enthusiast. Drives: 2015 Camaro ZL1 Summit White Join Date: Jan 2019 Location: Calgary Area, Alberta Posts: 221	Try a handheld vacuum pump on the actuator and see what that does. This Thread may help with some diagnostics. https://www.camaro5.com/forums/showt...&highlight=NPP __________________ Levon H. Bone Stock

07-03-2023, 11:26 PM	#3
FasNuf Drives: 2014 Camaro ZL1 Join Date: Jul 2019 Location: Oregon Posts: 1,617 View My Garage	I made a switch that has 3 modes. Auto (factory setting) Open, and closed. When in the closed position at morning start, it takes about 1 second for the valves to close and stay closed at idle so I don't think a ton of vacuum is needed. If you're interested how to connect an ON OFF ON type switch, watch my video below. Sorry had to edit and verify myself. If your fuel system has had the FPCM removed, this will disable the NPP., this is also known as K38 Chassis Control Module. Timestamp 2:32 in the video is the schmatic with the switch shown. . https://youtu.be/R1WfpAotXIY . . . . . . . __________________ . . . . https://www.youtube.com/channel/UCgN...etl17hA/videos Last edited by FasNuf; 07-03-2023 at 11:45 PM.

07-05-2023, 10:18 AM	#4
rmyers Drives: Both American Made Join Date: Feb 2008 Location: Texas Posts: 781	Thank you for my sharing. I was aware of the 3 mode mod, but not your video. This will be extremely helpful. 1st step for me though is making them work as intended. BTW, what manual were you referring to in the video? __________________ 2012 ZL1 #213 M6 Black on Black 2013 ZL1 #2638 Convertible Auto 2010 Chevrolet Suburban 2011 GMC Seirra HD Denali

07-06-2023, 09:26 AM	#6
rmyers Drives: Both American Made Join Date: Feb 2008 Location: Texas Posts: 781	I am pretty sure I solved the problem. It was so simple, its kind of embarrassing. Turned out to be a vacuum leak at the actuators. Now on to the 3-mode switch modification. __________________ 2012 ZL1 #213 M6 Black on Black 2013 ZL1 #2638 Convertible Auto 2010 Chevrolet Suburban 2011 GMC Seirra HD Denali

07-05-2023, 10:46 AM	#5
FasNuf Drives: 2014 Camaro ZL1 Join Date: Jul 2019 Location: Oregon Posts: 1,617 View My Garage	BTW, what manual were you referring to in the video?[/QUOTE] It's the 2014 Factory Service Manual. I think they're available online in digital form but I don't know.