Installed Borla/GM cat-back Exhaust System

Sean D · August 7, 2016

Well I received some news today from two different sources that said GM changed the design to have an internal bypass. One source was the vendor I purchased the exhaust from and the other was from Borla corporate. If you are purchasing new, the exhaust will not have the external bypass tubing. I'll let you know how it sounds when I have time to install this weekend. Thanks for the assistance.

So how dose it sound? Any different than the external bypass?

WilliamBos · August 7, 2016

So how is the sound in the cab? Can you lower the spare tire with the duals?

Waaazooo · August 7, 2016

So how is the sound in the cab? Can you lower the spare tire with the duals?

Yes the pipe goes up and over the spare.

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Blue-Audi · August 8, 2016

I don't know if it sounds any different that the one with the external bypass as I have never heard one except on youtube videos. The exhaust sounds great in V8 mode. Startup sounds great and then it quiets down as the engine idles down. The V4 mode sounds okay but not optimal. To my ear it sounds like a Suburu WRX in V4 mode. It's not exactly what a V8 truck should sound like. If the V4 mode starts bothering me I shift it into M7 and it goes away. Let me know if you have any other questions. Thanks.

Waaazooo · August 8, 2016

I don't know if it sounds any different that the one with the external bypass as I have never heard one except on youtube videos. The exhaust sounds great in V8 mode. Startup sounds great and then it quiets down as the engine idles down. The V4 mode sounds okay but not optimal. To my ear it sounds like a Suburu WRX in V4 mode. It's not exactly what a V8 truck should sound like. If the V4 mode starts bothering me I shift it into M7 and it goes away. Let me know if you have any other questions. Thanks.

Lol, I was thinking the same. I had several Wrx's/STi... But it's like the wrx at 1800 rpms driving uphill with my mother in law in the back seat. I still love the sound, but will probably let it go and keep my intake sound.

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rmichaly · November 19, 2016

Hi All

I am new to the forum and am interested in the GM\Borla cat back system for my 2014 Silverado with a 5.3L. I am really gun shy at this point because I had the Borla Touring cat back exhaust from Borla on my 2009 Silverado and I hated it. The drone was overwhelming especially at highway speeds (1700 -2200 RPM). I had an exhaust shop install the flex pipe behind the cat and added a resonator which helped slightly but not enough where I could live with it. I would like it to be quiet in the cab when cruising and a bit of a rumble on acceleration but as close to stock as possible. Will the GM\Borla Cat back system meet my criteria or should I just stick with the OEM exhaust system? I don't want to be disappointed again.

cbrsilv15 · November 19, 2016

You're looking for the Borla gmpp muffler then. I have the sport and my resonator cut out with the flap clamped

Open. Sounds perfect. Zero drone and not too loud either.

GMC_SD_Ult_16 · January 8, 2017

Is yours for a 5.3? I have a 6.2 and I got mine (love it by the way) last Saturday and mine has the small "bypass" tube.

Can anyone that has the bypass tube tell me the size of pipe - O.D.? I have a muffler delete on a 6.2L and moved the resonator in front of the adaptive valve (flapper) where OEM muffler was located.. Sounds great at idle with flapper open but drones when cruising... With flapper closed at idle get a raspy sound from the flapper. I will be doing something different possibly a GM Borla but now I am looking to experiment a little.. Thanks for humoring my possible next try. Trying to see if adding the bypass possible removes enough pressure that the valve does not rattle but doesn't let it drone at Hwy speeds either. GM/Borla added it around the bypass for some reason. Thanks again.

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GMC_SD_Ult_16 · January 8, 2017

Can anyone that has the bypass tube tell me the size of pipe - O.D.? I have a muffler delete on a 6.2L and moved the resonator in front of the adaptive valve (flapper) where OEM muffler was located.. Sounds great at idle with flapper open but drones when cruising... With flapper closed at idle get a raspy sound from the flapper. I will be doing something different possibly a GM Borla but now I am looking to experiment a little.. Thanks for humoring my possible next try. Trying to see if adding the bypass possible removes enough pressure that the valve does not rattle but doesn't let it drone at Hwy speeds either. GM/Borla added it around the bypass for some reason. By the way I saw someone earlier in the thread say one (1) inch but later they said they did not measure it. Thanks for confirming if at all possible.

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wuznme · January 8, 2017

1.5 OD

8.125 center to center
2.25 height of pipe

Dnt · January 8, 2017

I am pretty much happy with the GM Borla Catback exhaust dealer installed system. Approx 9000 miles so far. The only issue that I had is that I did not like the V4 exhaust note at low speeds. (below 50mph) so I bought a Hypertech hand held tuner on sale a autoanything and used it to set the AFM to only come on at above 50mph Sounds great to me For some reason this 2016 6.2 8spd 3.23 geared truck likes to stay in V4 mode a LOT at low speeds I like the way that is is quiet at idle and mid throttle but anything above that awakens the beast and it roars nicely. Cannot have a REDNECK "wake the neighborhood" exhaust on a gentlemen's PU truck like a Denali............Come on

Man

I recently added a Cold Air Intake system, the CAI combined with the catback exh makes some awesome music together. Lovin It

Gas mileage is pretty darn good for a 6000lb 445hp behemoth also check this out

GMC_SD_Ult_16 · January 8, 2017

1.5 OD

8.125 center to center

2.25 height of pipe

Great information and thanks so much... I am not sure if matters but are you running a 6.2L or 5.3L? Also what is height of pipe measurement you mention at 2.25? I understand the other measurements. Thanks again.

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