Longtubes + catless X + factory npp
Thread Starter
Advanced
Joined: Apr 2015
Posts: 57
Likes: 0
From: NC
Longtubes + catless X + factory npp
Looking at getting this setup for my 11 C6 6m. I have the mild to wild switch and I'm sure the wild side will be great. I'm mainly curious if the mild side will have drone or not, as I'm positive the wild side will drone. I'm sure someone is/has ran this setup. Thanks for any input. I'll also being getting it dyno tuned if that makes a difference.
Burning Brakes
Joined: Aug 2014
Posts: 1,240
Likes: 258
From: Tampa FL
I too plan longtube and catless X on an 11 A6 G.S. with duel. Thinking (KOOKS) would love to hear other opinions.
And yes it also will be Dynoed.
And yes it also will be Dynoed.
Last edited by HK770; Aug 2, 2015 at 12:34 PM.
Race Director
Joined: Sep 2007
Posts: 16,557
Likes: 2,108
From: Peoria/Phoenix AZ
C6 of Year Finalist (performance mods) 2019
You're still going to get drone in the 1400-1700 RPM range, but it will just be louder. It's why you should have a controller for your NPP option to choose between kinda loud and really loud. 
Thread Starter
Advanced
Joined: Apr 2015
Posts: 57
Likes: 0
From: NC
Thanks for the info, I went with a cat less X on my old 04 GT mustang and never had a problem with the smell, should I expect worse with the ls3?
Race Director
Joined: Sep 2007
Posts: 16,557
Likes: 2,108
From: Peoria/Phoenix AZ
C6 of Year Finalist (performance mods) 2019
The drone you currently have in either mode will simply be louder. A tune won't change that.
Been there, done that, with well over 100K miles of experience.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Thread Starter
Advanced
Joined: Apr 2015
Posts: 57
Likes: 0
From: NC
OK, well currently with the flaps closed it's dead quiet, no drone at all, so, wondering how much that will change.
Advanced
Joined: Aug 2014
Posts: 88
Likes: 3
From: Corrales New Mexico
I can't address the drone issue but as far as the smell of fuel goes I have recently installed a set of long tubes with a cat delete X pipe and the only time the smell of fuel is evident is when it's first started while in my garage maybe there's some truth to the smell issue depends on ones tune.
Thread Starter
Advanced
Joined: Apr 2015
Posts: 57
Likes: 0
From: NC
Thanks suds, exactly what I was looking for. How much louder over stock do the longtubes take it with factory npp and flaps open??
Thread Starter
Advanced
Joined: Apr 2015
Posts: 57
Likes: 0
From: NC
Oh yeah I have the mild to wild switch and generally ride around in wild mode, I'm just looking for wild to be alot louder along with the power gains.
Burning Brakes
Joined: Nov 2010
Posts: 1,008
Likes: 12
From: The only state to ever kick another country's ass! TEXAS
I just did this. Added a supercharger and it was recommended to loose the cats. With the cats gone, my Magnaflow exhaust had a pretty bad drone around 1500-1600 rpm's. I changed to a 2013 NPP exhaust this week. I didn't want to buy the NPP in a box, so I just connected the flaps to manifold vacuum. The drone I was experiencing went away, but if I lugged the engine a little and accelerated, the manifold vacuum would drop enough so the flaps started to open and I would get the drone. Not as bad as the Magnaflow, but still too much for normal driving and long trips. I added a check valve to the vacuum line, and now the flaps don't open at all and the drone is completely gone. They don't even open after sitting overnight. My wife says it's quieter than the Magnaflow was when the rest of my exhaust was still stock, and she has sensitive hearing. I'll be adding a solenoid in the next week or so, to give me the capability to open the flaps when I want, and yet retain to ability to keep them completely closed for "wife approved" cruising. Hope this helps you.
Last edited by Xtremespeed; Aug 2, 2015 at 07:41 PM.
Racer
Joined: Jan 2013
Posts: 471
Likes: 62
From: Caliente Houston Tejas
Burning Brakes
Joined: Nov 2010
Posts: 1,008
Likes: 12
From: The only state to ever kick another country's ass! TEXAS
Drifting
Joined: Oct 2004
Posts: 1,790
Likes: 29
From: STL MO
St. Jude Donor '09-'10
I had 0 drone with the flaps closed on my heads and cam'ed C6, car was pretty loud with flaps open and had a load drone between 1200-2200 rpm iirc. I ran American Racing headers with high flow cats and had a mild to wild setup as well.
You should have little to no drone driving around with the flaps closed.
You should have little to no drone driving around with the flaps closed.