[Bearded_Seamonkey]

So I have a 2022 ZL1 1LE on order and I'm obviously reading about upgrades. I plan to eventually add an exhaust...borla, corsa or awe. The NPP debate is real...I've read why people like it and why people can do without it. The part I'm a little confused about is at startup. I've read that the valve opens to warm up the cat before it quiets down. So if I have a borla or corsa with npp, does that mean it will be crazy loud for the first minute or so before it quiets down? Most people use the "friendly neighbor" reason for npp and if it starts wide open doesn't that defeat the purpose?

[LiqTenExp]

It will "roar" a little upon startup. You can work around this by enabling stealth mode of the NPP flaps. If you go further into modifications and require tuning further steps can be taken to reduce/eliminate it.

I definitely recommend getting an exhaust with NPP if you have the NPP option, lot more versatility in sound control.

[Bearded_Seamonkey]

Originally Posted by LiqTenExp

It will "roar" a little upon startup. You can work around this by enabling stealth mode of the NPP flaps. If you go further into modifications and require tuning further steps can be taken to reduce/eliminate it.

I definitely recommend getting an exhaust with NPP if you have the NPP option, lot more versatility in sound control.

Can you elaborate on the versatility? Does that mean go with a louder exhaust (atak over the s-type) since the npp can quiet it down if needed?
Thanks

[LiqTenExp]

Originally Posted by Bearded_Seamonkey

Can you elaborate on the versatility? Does that mean go with a louder exhaust (atak over the s-type) since the npp can quiet it down if needed?
Thanks

For example, my car is NASCAR loud, shaking windows loud in Track in 1-4 gears. But on the highway with my Borla Sport and NPP closed (happens while cruising in 6th) it is wife approved, barely sounds like an aftermarket exhaust is there. I can choose to be in stealth mode with NPP closed around town in 1-4 and generally not turn too many heads at all due to the volume. The amount of dynamic range you get out of the exhaust is extreme!

Car has 1-7/8" LT, no cats, full 3" borla sport exhaust w/NPP, cam, bigger blower, etc etc etc

[Hambo864]

Originally Posted by Bearded_Seamonkey

So I have a 2022 ZL1 1LE on order and I'm obviously reading about upgrades. I plan to eventually add an exhaust...borla, corsa or awe. The NPP debate is real...I've read why people like it and why people can do without it. The part I'm a little confused about is at startup. I've read that the valve opens to warm up the cat before it quiets down. So if I have a borla or corsa with npp, does that mean it will be crazy loud for the first minute or so before it quiets down? Most people use the "friendly neighbor" reason for npp and if it starts wide open doesn't that defeat the purpose?

There are 4 modes. Tour, Sport, Track, and Snow/Ice.

Snow/Ice is considered "Stealth". In order to start your car with the valves closed, you have to have the car in that Snow/Ice mode. This will negate the loud start. The valve being open to warm the cat is just for about a second and a half. If you have it in any say tour mode, it will fire up loudly and then the valves close and its quiet. If you have it in any other mode, yes, it definitely defeats the purpose of using it to be a friendly neighbor.

The stock NPP exhaust sounds really good. The problem with it is the ECM will automatically close the valves at various points to help with drone. There are a few ways to change this.

The first being pull the fuse. Doing so, you will lose your ability to actuate the valves. The second way is using a mild to wild controller. Some people love them, some people hate them. The best way to control the valves is by using HPTuners. You can set them to open or close however you like.

I bought the Corsa NPP with the double X pipe. With the NPP closed, you can barely hear the car. With it open, its not much louder than stock until you go WOT, then its considerably louder. With the valves closed, it is much more quiet than the factory NPP. Its almost mind numbing to hear the difference. In my opinion, if you are going to get an aftermarket NPP exhaust, you need to get HPTuners to adjust the valves. If not, you're going to put the car into 4th and its randomly going to go from sounding really good to no noise at all. The valves close when the ECM tells it to and there is so much difference in the two its kind of annoying.

Some people love the ability to have the stealth mode, others find it useless. I wouldn't have my car any other way than the various exhaust modes.

[esm]

For reference, I deleted the secondary cats with a Borla X-pipe before they discontinued it and everything else in the exhaust is stock. I have a friend that installed a Borla Atak catback with midpipes but keeping all 4 cats, his car sounds similar to mine both inside and out. My car is just a little bit louder overall, but with the valves closed on the highway, my car still sounds stock. The only way to have quite cold starts is to put the exhaust in Stealth Mode before you shut it off.

[Wuiquen]

Originally Posted by esm

For reference, I deleted the secondary cats with a Borla X-pipe before they discontinued it and everything else in the exhaust is stock. I have a friend that installed a Borla Atak catback with midpipes but keeping all 4 cats, his car sounds similar to mine both inside and out. My car is just a little bit louder overall, but with the valves closed on the highway, my car still sounds stock. The only way to have quite cold starts is to put the exhaust in Stealth Mode before you shut it off.

So as long as I put the car back on stealth before turning off, it will start on that mode without opening the valve for cold start?

[Wuiquen]

I feel like these exhaust modes are backwards. Why close the valves at higher RPMs versus opening them up while keeping them closed at lower RPMs?

[LiqTenExp]

Originally Posted by Wuiquen

So as long as I put the car back on stealth before turning off, it will start on that mode without opening the valve for cold start?

Correct

[LiqTenExp]

Originally Posted by Wuiquen

So as long as I put the car back on stealth before turning off, it will start on that mode without opening the valve for cold start?

Not sure what you are talking about.

They will open even in Stealth mode if load/rpm placed on engine is high enough. They will always eventually open if you go WOT. They close at higher speed in higher gears when load/rpm is low to keep highway cruising quieter.

[LT4Greg]

If you set the exhaust mode to Track and pull the fuse-51 it will be loud on cold start and louder while driving. I set my exhaust to Track and it blasts off when starting after sitting overnight or in the evening when leaving work. After it warms up it quiets down.

[Bearded_Seamonkey]

Originally Posted by Hambo864

There are 4 modes. Tour, Sport, Track, and Snow/Ice.

Snow/Ice is considered "Stealth". In order to start your car with the valves closed, you have to have the car in that Snow/Ice mode. This will negate the loud start. The valve being open to warm the cat is just for about a second and a half. If you have it in any say tour mode, it will fire up loudly and then the valves close and its quiet. If you have it in any other mode, yes, it definitely defeats the purpose of using it to be a friendly neighbor.

The stock NPP exhaust sounds really good. The problem with it is the ECM will automatically close the valves at various points to help with drone. There are a few ways to change this.

The first being pull the fuse. Doing so, you will lose your ability to actuate the valves. The second way is using a mild to wild controller. Some people love them, some people hate them. The best way to control the valves is by using HPTuners. You can set them to open or close however you like.

I bought the Corsa NPP with the double X pipe. With the NPP closed, you can barely hear the car. With it open, its not much louder than stock until you go WOT, then its considerably louder. With the valves closed, it is much more quiet than the factory NPP. Its almost mind numbing to hear the difference. In my opinion, if you are going to get an aftermarket NPP exhaust, you need to get HPTuners to adjust the valves. If not, you're going to put the car into 4th and its randomly going to go from sounding really good to no noise at all. The valves close when the ECM tells it to and there is so much difference in the two its kind of annoying.

Some people love the ability to have the stealth mode, others find it useless. I wouldn't have my car any other way than the various exhaust modes.

Thanks for the detailed response. I don't plan to get a tune until the warranty is up. I'm leaning towards borla and plan to keep the npp after all of the clarifications. Not sure whether it will be the atak or s-type.

[Hambo864]

Originally Posted by Bearded_Seamonkey

Thanks for the detailed response. I don't plan to get a tune until the warranty is up. I'm leaning towards borla and plan to keep the npp after all of the clarifications. Not sure whether it will be the atak or s-type.

No problem. I answered a little more than you needed but I wanted to help someone else out that may be wondering about similar things.


Sent from my iPhone using Tapatalk

[LiqTenExp]

Go Borla Sport. If you do further mods like LT you will wish you didn't get Attack.