NPP closed back pressure
Le Mans Master
Joined: Oct 2012
Posts: 8,434
Likes: 411
From: Texas
If you accelerate at say 2/3 throttle in a single gear with NPP as stock opening at around 3800 rpm, the very moment those flaps open the car will lunge forward with a solid 30+ hp gain. It's instant and very easy to feel in my 500 rwhp LS3.
The NPP makes 6 more hp than the stock non-NPP exhaust when open at peak power. But the stock non-NPP exhaust must flow much better than the a closed NPP because closed NPP makes a solid 30 rwhp less.
The NPP makes 6 more hp than the stock non-NPP exhaust when open at peak power. But the stock non-NPP exhaust must flow much better than the a closed NPP because closed NPP makes a solid 30 rwhp less.
Melting Slicks
Joined: Apr 2013
Posts: 2,691
Likes: 140
I have a stock (kinda) LS3 (meaning it only has headers and a tune), and I routinely run with my NPPs forced "closed" by the Dashlogic device, just because I don't want to draw loud attention to myself most times.
Seat of the pants, I cannot tell any difference between fully open NPP and fully closed NPP. Even grabbing the gears, it feels about the same amount of wheel spin too.
So my bet is, it is not much of a HP loss between full open NPP and full closed NPP on an LS3, certainly not 40 HP
Now if I get to installing a supercharger, I'll monitor my AFR and compare to see what it is really doing to the engine, before I run fully closed for any period of time under load.
Seat of the pants, I cannot tell any difference between fully open NPP and fully closed NPP. Even grabbing the gears, it feels about the same amount of wheel spin too.
So my bet is, it is not much of a HP loss between full open NPP and full closed NPP on an LS3, certainly not 40 HP
Now if I get to installing a supercharger, I'll monitor my AFR and compare to see what it is really doing to the engine, before I run fully closed for any period of time under load.
Pro
Joined: Nov 2014
Posts: 537
Likes: 44
From: San Diego/Pacific Beach CA
Thread Starter
Advanced
Joined: Mar 2010
Posts: 78
Likes: 0
From: Houston TX
I had the NPPs installed and temporarily wired the valve to stay closed all the time until I can install the NPP in a box kit over the next week or so.
Only thing that happened so far was under the first WOT acceleration, the catback separated from the x pipe where the clamp is so i had to go back and had it tac welded.
Seat of the pants I've not noticed anything definite as far as power changes over the Borla system swap out, so still not so sure about some of the 40hp claims that a few say should be lost - but then again my butt dyno isn't the most technically accurate form of measurement.
My biggest concern was that I not do any lasting damage by forcing closed the NPP exhaust on my set up full time - if suspicions are that its fattening up at WOT I suppose that's not so bad, it's leaning out that I've always been wary of.
Only thing that happened so far was under the first WOT acceleration, the catback separated from the x pipe where the clamp is so i had to go back and had it tac welded.
Seat of the pants I've not noticed anything definite as far as power changes over the Borla system swap out, so still not so sure about some of the 40hp claims that a few say should be lost - but then again my butt dyno isn't the most technically accurate form of measurement.
My biggest concern was that I not do any lasting damage by forcing closed the NPP exhaust on my set up full time - if suspicions are that its fattening up at WOT I suppose that's not so bad, it's leaning out that I've always been wary of.
Last edited by Ryoga23; Apr 1, 2016 at 10:08 AM.
Safety Car
Joined: Nov 2006
Posts: 3,667
Likes: 159
My thinking is, when you get in the 450 and up rwhp areas, it will continue to show a bigger difference between fully open and fully closed.
And, the next time(s) I find someone in a C6 doing dyno pulls, I'll plug in my device and get us some more data too!
Race Director
Joined: May 2004
Posts: 16,667
Likes: 1,209
From: Raleigh, NC
St. Jude Donor '15
Melting Slicks
Joined: Apr 2013
Posts: 2,691
Likes: 140
Yea, and I am not trying to discredit Dashlogic in any way either, because they have the proof for their setup
My thinking is, when you get in the 450 and up rwhp areas, it will continue to show a bigger difference between fully open and fully closed.
And, the next time(s) I find someone in a C6 doing dyno pulls, I'll plug in my device and get us some more data too!
My thinking is, when you get in the 450 and up rwhp areas, it will continue to show a bigger difference between fully open and fully closed.
And, the next time(s) I find someone in a C6 doing dyno pulls, I'll plug in my device and get us some more data too!
* without any data to backup the claim, so it is theory.
Racer
Joined: Jul 2015
Posts: 297
Likes: 8
Local guy's 08 LS3 h/c and retro fit NPP mufflers with the M2W independent, non-can connected controller box did back to back pull's opened and closed. I don't recall exact numbers or have the graph but I recall it made ~10 more HP under 5000rpm and lost ~10 over 5000rpm (20hp difference over 5000). something to that extent. Car made almost 500whp (with npp opened)
Last edited by JasonCzerak; Apr 9, 2016 at 10:35 AM.
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