NPP feels slower.????
Thread Starter
Racer
Joined: Nov 2004
Posts: 412
Likes: 26
NPP feels slower.????
I just installed an NPP exhaust on my base ls3 car and now it feels slower. Maybe its all in my head but it just doesn't seem to pull as hard. My car has a veraram,1 7/8 headers,a yank converter and tuned and has run 11.0 @123.
Maybe its just me? I'm going to log a couple of pulls and see if anything is going on but I was just wondering if anyone else has had this.
Maybe its just me? I'm going to log a couple of pulls and see if anything is going on but I was just wondering if anyone else has had this.
Team Owner
Joined: Dec 2008
Posts: 35,874
Likes: 1,600
From: Honolulu HI
Doubt anything changed...but what axle-back system was on the car before? Are the valves opening/operating as they should? Maybe they're sticking closed.
Last edited by MTPZ06; Nov 7, 2017 at 09:10 PM.
Thread Starter
Racer
Joined: Nov 2004
Posts: 412
Likes: 26
It just had the base system before and I haven't hooked up the vacuum to it yet so its open all the time. Im sure its all in my head but it doesnt feel like it pulls as hard.
Drifting
Joined: May 2015
Posts: 1,525
Likes: 391
From: Martinez CA
..I had a similar experience with a truck, once. It was an off-road built truck, and I installed some Flow Masters. It made a lot of noise, but seemed slower. I didn't like it making a ton of exhaust noise, but not being fast, so I swapped back...
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Le Mans Master
Joined: Oct 2012
Posts: 8,434
Likes: 411
From: Texas
Nope.
It's dynoed about 30 hp slower until those valves open. Its all a loss.
You can feel it easily too. Hold your NPP equipped car in about 2nd gear at about 2/3 throttle and as soon as those valves open the car lunges forward, about 30-40 rwhp worth.
This was one of the main reasons I went to a Corsa. You get all your power all of the time and it's very noticeable just around town. Also it was lighter, sounds much better, no drone, and is SS. If the Corsa was just a bit quieter it would be perfect.
It's dynoed about 30 hp slower until those valves open. Its all a loss.
You can feel it easily too. Hold your NPP equipped car in about 2nd gear at about 2/3 throttle and as soon as those valves open the car lunges forward, about 30-40 rwhp worth.
This was one of the main reasons I went to a Corsa. You get all your power all of the time and it's very noticeable just around town. Also it was lighter, sounds much better, no drone, and is SS. If the Corsa was just a bit quieter it would be perfect.
Race Director
Joined: Jul 2005
Posts: 12,034
Likes: 3,568
From: Central MO
Nope.
It's dynoed about 30 hp slower until those valves open. Its all a loss.
You can feel it easily too. Hold your NPP equipped car in about 2nd gear at about 2/3 throttle and as soon as those valves open the car lunges forward, about 30-40 rwhp worth.
This was one of the main reasons I went to a Corsa. You get all your power all of the time and it's very noticeable just around town. Also it was lighter, sounds much better, no drone, and is SS. If the Corsa was just a bit quieter it would be perfect.
It's dynoed about 30 hp slower until those valves open. Its all a loss.
You can feel it easily too. Hold your NPP equipped car in about 2nd gear at about 2/3 throttle and as soon as those valves open the car lunges forward, about 30-40 rwhp worth.
This was one of the main reasons I went to a Corsa. You get all your power all of the time and it's very noticeable just around town. Also it was lighter, sounds much better, no drone, and is SS. If the Corsa was just a bit quieter it would be perfect.
Safety Car
Joined: Nov 2007
Posts: 4,433
Likes: 873
From: Bay Area CA
The NPP does not lose power when closed, just gains 6 hp and 4 ft. Lbs when open. Both systems have 2 1/2” pipes, NPP just has a by-pass pipe in muffler.
Thread Starter
Racer
Joined: Nov 2004
Posts: 412
Likes: 26
You stated the vacuum lines are not hooked up, but are any vacuum sources open? Vacuum Lines or intake manifold port creating a vacuum leak?
The NPP does not lose power when closed, just gains 6 hp and 4 ft. Lbs when open. Both systems have 2 1/2” pipes, NPP just has a by-pass pipe in muffler.
The NPP does not lose power when closed, just gains 6 hp and 4 ft. Lbs when open. Both systems have 2 1/2” pipes, NPP just has a by-pass pipe in muffler.
Safety Car
Joined: Nov 2007
Posts: 4,433
Likes: 873
From: Bay Area CA
Ok, I wasn't sure. I mentioned it because after I had service done at the dealership they forgot to hook up the vacuum lines on the valve tips. The exhaust stayed open and power felt down due to the vacuum leak.
Race Director
Joined: Nov 2003
Posts: 16,066
Likes: 4,148
From: Bergen county NJ
Fwiw..if I leave the no open all the time with the no the vehicle seems slower...if I run as the car was designed the vehicle feels quicker...and then once in awhile I leave it open for short periods of time the car feels quicker.
I don't know if it's the knock sensors,,or the air fuel reads by o2 sensors or what but just what I've found over time..
I would imagine with 1 7/8 headers ..your cars exhaust is pretty free flowing....maybe having the npp open all the time is too much? Try driving around with the flaps closed or use the original set up where they open at around 3500 rpm..
Imo reduced air flow out the exhaust is good for low rpm torque..high flowing exhaust is good for high rpm...
I could be totally wrong but I believe one of these is what your experiencing,,,
I don't know if it's the knock sensors,,or the air fuel reads by o2 sensors or what but just what I've found over time..
I would imagine with 1 7/8 headers ..your cars exhaust is pretty free flowing....maybe having the npp open all the time is too much? Try driving around with the flaps closed or use the original set up where they open at around 3500 rpm..
Imo reduced air flow out the exhaust is good for low rpm torque..high flowing exhaust is good for high rpm...
I could be totally wrong but I believe one of these is what your experiencing,,,