[WorthFlorida]

Every forum and ad’s about NPP Dual Exhaust is to keep things loud. My only issue and it seems others have the same problem, is on startup it is at full open bypass. Too damn noisy at 6:30am on the driveway when wanting to go to a car show. In system setup if you program it for Sealth only, still on startup after it has sat a while or cooled down, the exhaust is at full open bypass. After about 10 seconds it does quiet down. In system settings this keeps it in the Stealth mode regardless if you are in Touring, Sport or Track.

Does anyone know if this can be changed? Can a tuner shop make the change? I love the dual exhaust and have it in Sport mode most of the time, but start up is a killer. After 1400 miles, I’m now getting the rattle and vibrations from start up until the exhaust changes mode. My thinking is that the engineers tuned the engine fuel air mixture for wide open exhaust only.

[enzia35]

The super loud start up is for emissions. More fuel to heat up the cats faster.

[VinnAY]

It has that initial bark no matter the setting just degrees of volume but "Stealth" (LOLOL) still has a bark to it.

[6spdhyperblue]

You can have a tuner change it to start with the valves closed. The work around on a stock car is to hold the start button Until it powers up with your foot off the Clutch and brake. Then use the mode selector to go snow ice. Then put your foot on the brake or clutch and hit the start button

[Zr8000]

I don’t think it will make much difference. My standard exhaust barks pretty good when it starts up.

[ember1205]

Originally Posted by 6spdhyperblue

You can have a tuner change it to start with the valves closed. The work around on a stock car is to hold the start button Until it powers up with your foot off the Clutch and brake. Then use the mode selector to go snow ice. Then put your foot on the brake or clutch and hit the start button

You can also just go into the NPP settings and direct-select Stealth mode. Once you hear the valve actuate, it's closed, and the startup will be at its minimum value.

If you shut the car off in Stealth mode, then it should flip the butterfly closed either just ahead of, or very close to, actual startup if it isn't closed already.

[SSDan]

Originally Posted by enzia35

The super loud start up is for emissions. More fuel to heat up the cats faster.

This. I agree with others that other than forcing it into stealth mode prior to start there is little way to quiet the car down at start. The high rpm bark and high idle will still happen regardless of NPP exhaust mode or even exhaust type (along with a double pulse on the injector cycle for the first several seconds). All of this is there to make the car run super rich at a cold start up so the cats heat up quickly and become effective enough to pass EPA standards.

A tuner might be able to tune out this high rpm/high fuel load at cold start but I wouldn't suggest do it unless you are willing to run with no cats.

[Aragorn]

What the other member said, shut it off in stealth and it should restart in stealth. That might help.

[trohde78]

Originally Posted by Aragorn

What the other member said, shut it off in stealth and it should restart in stealth. That might help.

+1

This is the only method I've found to keep the valves closed at startup. What's frustrating is that you can't select it before startup, only when the car is running.

[ember1205]

Originally Posted by trohde78

+1

This is the only method I've found to keep the valves closed at startup. What's frustrating is that you can't select it before startup, only when the car is running.

I recall seeing a video showing exactly how to select the mode BEFORE starting the car but can't find it. Essentially, you press the start button WITHOUT putting your foot on the brake (it won't start). Once the car powers on, go into the settings management to choose the Stealth mode. Wait / listen for the actuators to engage and close. Start the car.

[h018871]

I've found info that the valves are controlled via pulse width modulation generated by the chassis control module. See the attached diagram.
My car starts up loud even in snow/ice mode for the first few seconds. Also the vehicle menu is not available unless the car is running. Pushing the start button once or twice without a foot on the brake doesn't enable the menu either. The only way I've found is to put the car in stealth mode before shutting it off. So far, I'm not real good at remembering that.


A lengthy description of how it works:
Exhaust Tailpipe Flow Control Valve System
The exhaust tailpipe flow control system is used to tune the exhaust
note for high performance vehicles. The vehicle is equipped with two
tailpipe exhaust valves. One in the left tailpipe and one in the right
tailpipe. Each exhaust tailpipe valve is installed in the low
restriction exhaust path of a dual outlet muffler, near the exhaust tip.
When a tailpipe exhaust valve is open, the low restriction exhaust
path is opened to the atmosphere, and the exhaust note becomes more aggressive.
An output circuit from the chassis control module is used to control the
actuator that opens the left and right exhaust tailpipe valves. The
exhaust flow control valve opens and closes when the chassis control
module commands the actuator by pulse width modulation of the control signal.
To provide a more aggressive exhaust note when the vehicle is started,
the exhaust tailpipe valves are opened during an engine crank event
during specific modes of operation if that option is available. Once
the engine is running, accelerator pedal position, transmission gear
and engine speed are used to determine the commanded state (open or closed)
of the exhaust tailpipe valves.
There are four specific exhaust performance modes that result in different
behavior of the exhaust tailpipe valves. These modes are:
Note: You may notice an exhaust tone change due to the AFM system activation,
or during certain driving conditions to meet Federal noise pass-by regulations.
Review the cylinder deactivation exhaust flow control system operational
modes listed below for additional details.
Winter/Eco Mode: Exhaust tailpipe valves will be closed at all times when
the engine is running.
Tour Mode: Exhaust tailpipe valves are closed when the engine is idling and
during normal/non-aggressive driving. Valves open during aggressive driving.
Sport Mode: Exhaust tailpipe valves are open when the engine is idling and
during most driving scenarios. See note above.
Track Mode: Exhaust tailpipe valves are open at all times. See note above.
It is possible to personalize the exhaust sound. When engine sound
enhancement is turned off via the personalization menu, the exhaust
tailpipe valves will be put into track mode no matter which vehicle
mode (Winter/Eco, Tour, Sport, or Track) is displayed on the drivers
instrument panel.


I don't know if putting a constant 12vdc signal to the control valve will close it or cause the module to fail (ie burn up). There is a calibration procedure if the valve module is replaced, implying that it is not an on/off type of valve.......the programming could have "partial open at xx%" modes while driving.
I'd like to see if it works, but don't want to burn up the module/controller.

[GOMD]

If you hold the start button down for about 5-6 seconds, without pressing the brake pedal, the car will turn on in "service mode". It powers up all electronics basically, and you can then switch to "stealth" in the radio, or toggle to touring or snow mode on the center console.

[ember1205]

Originally Posted by ember1205

I recall seeing a video showing exactly how to select the mode BEFORE starting the car but can't find it. Essentially, you press the start button WITHOUT putting your foot on the brake (it won't start). Once the car powers on, go into the settings management to choose the Stealth mode. Wait / listen for the actuators to engage and close. Start the car.

Stumbled across it again just now!

[avalonandl]

Originally Posted by ember1205

I recall seeing a video showing exactly how to select the mode BEFORE starting the car but can't find it. Essentially, you press the start button WITHOUT putting your foot on the brake (it won't start). Once the car powers on, go into the settings management to choose the Stealth mode. Wait / listen for the actuators to engage and close. Start the car.

This is the method.

I select this when I have to leave my condo before 6 am.....