NPP vs Non-Npp/Base Muffler Cans
Thread Starter
Burning Brakes
Joined: Jun 2003
Posts: 846
Likes: 105
From: Knoxville TN
NPP vs Non-Npp/Base Muffler Cans
Tried searching with no luck. Talking about NPP vs Base, NOT the Z06/ZR1 mufflers.
Is there a difference in the muffler cans themselves between the base NPP and the base mufflers without the npp.
Is there a difference in the muffler cans themselves between the base NPP and the base mufflers without the npp.
Burning Brakes
Joined: Jun 2005
Posts: 913
Likes: 129
From: Toronto
Thread Starter
Burning Brakes
Joined: Jun 2003
Posts: 846
Likes: 105
From: Knoxville TN
Trying to figure out if non-npp can is less restrictive than npp closed.
Le Mans Master
Joined: Dec 2005
Posts: 6,999
Likes: 1,685
From: Southeast TX
I can tell you that NPP's closed fall 20hp short of NPP's open. That's on a 470rwhp cam and bolt on LS3. Saw that on a dyno. NPP's open get you an extra 6 hp vs stock narrow body mufflers on a stock LS3...per GM. I suspect that difference may grow if/when you had HP.
Thread Starter
Burning Brakes
Joined: Jun 2003
Posts: 846
Likes: 105
From: Knoxville TN
I can tell you that NPP's closed fall 20hp short of NPP's open. That's on a 470rwhp cam and bolt on LS3. Saw that on a dyno. NPP's open get you an extra 6 hp vs stock narrow body mufflers on a stock LS3...per GM. I suspect that difference may grow if/when you had HP.
Le Mans Master
Joined: Dec 2005
Posts: 6,999
Likes: 1,685
From: Southeast TX
I'm assuming you have NPP in a box to control the mufflers. If so, the controller is in your right hand cubby just inside the trunk. Take the controller out of the system by hooking the vacuum feed from the engine direct to the vacuum line going to the mufflers. You're just by-passing the controller. You'll have to cut the line going from the box to the mufflers as it's connected inside the controller. Just cut it as long as possible in case you want to put the controller back in the loop. The hose from the engine is connected by a hose barb on the outside of the box. It just pulls off. You may have a zip tie there that you'll need to cut off. You'll need a vacuum line butt connector that is made for different size vacuum lines as the line going to the mufflers is much smaller than the line coming from the engine. They are commonly available at just about any auto parts store. This is about a 1 minute job that's cheap, easily done, and easily reversible.
Running it this way means your NPP's are closed anytime there is 5" of vacuum or more at the engine. Just driving abound easy and it's quiet. The moment you step on it hard, they will open immediately.
Running it this way means your NPP's are closed anytime there is 5" of vacuum or more at the engine. Just driving abound easy and it's quiet. The moment you step on it hard, they will open immediately.
Thread Starter
Burning Brakes
Joined: Jun 2003
Posts: 846
Likes: 105
From: Knoxville TN
I'm assuming you have NPP in a box to control the mufflers. If so, the controller is in your right hand cubby just inside the trunk. Take the controller out of the system by hooking the vacuum feed from the engine direct to the vacuum line going to the mufflers. You're just by-passing the controller. You'll have to cut the line going from the box to the mufflers as it's connected inside the controller. Just cut it as long as possible in case you want to put the controller back in the loop. The hose from the engine is connected by a hose barb on the outside of the box. It just pulls off. You may have a zip tie there that you'll need to cut off. You'll need a vacuum line butt connector that is made for different size vacuum lines as the line going to the mufflers is much smaller than the line coming from the engine. They are commonly available at just about any auto parts store. This is about a 1 minute job that's cheap, easily done, and easily reversible.
Running it this way means your NPP's are closed anytime there is 5" of vacuum or more at the engine. Just driving abound easy and it's quiet. The moment you step on it hard, they will open immediately.
Running it this way means your NPP's are closed anytime there is 5" of vacuum or more at the engine. Just driving abound easy and it's quiet. The moment you step on it hard, they will open immediately.
I was thinking of ditching the NPP for a base muffler but was wondering how much more restrictive the base muffler is compared to an NPP open.
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