6.6L L8T Gas Exhaust Options - MBRP, Borla...

[OS RR]

Offset/Offset or Offset/Center? 5x11 case? (I think magnaflow makes a 5x8 as well).

 

Was doin some dig'n, there is a enough room on the tail pipe (where it starts down after coming over the axle) for about a 9" resonator. I may go that route. Was looking at this one.

[Epsilon Plus]

Apparently, the Vibrant Ultra Quiet comes highly recommend across the web. 

 

Also, proper placement is between the muffler and cats from what I've read. After muffler at the tail pipe does nothing for the drone reduction goal.

[Epsilon Plus]

From Vibrant on a Summit review:

 

"

• Size. The general rule of thumb with Vibrant resonators/mufflers is that the larger the body of the device, the more effective it will be at reducing decibel levels, drone, rasp, etc. Larger volume of packing = more harmonic wave absorption. Aside from the volume of packing material making it more effective, is the shape. This is also part of the reason that the Ultra Quiet is a popular choice over bottle style resonators or round body mufflers. Each time your exhaust valve opens, an exhaust pulse wave travels down your exhaust stream. It bounces in all directions as it moves through the exhaust system. The frequency can be affected by the shape, size and length of chambers, tubing, etc. When the pulse wave meets a suppressive device with packing material, it is dampened as it travels through the perforated core, into the packing material, reflects off the outside wall and back through the packing material to rejoin the exhaust system. In a round suppressive device, the distance for the pulse wave to travel from core to outer body is uniform, compared to the Ultra Quiet resonator which has an oval shape with variable distances for the pulse wave to travel through. This makes it more effective at attenuating a broad spectrum of frequencies of the exhaust note. The same principle applies to a chambered suppressive device but placement becomes very important because the lack of packing material removes the ability to dampen vibration as the pulse wave travels through the chambers. They rely only on pulse wave reflection to cancel out frequencies. Also, keep in mind that a larger diameter tube can lead to an increase in drone/resonance since there is a larger underdamped surface area that can cause the sound waves to amplify.
• Placement. This also plays a key role in regards to reducing exhaust drone. For most applications we recommend placement of a resonator in the area under the front seats of the vehicle. Targeting this placement will be effective for drone frequencies that are exhibited at low to mid-range steady state throttle/engine load conditions (ie: highway driving). In many applications the room available for a resonator in this area is limited, so smaller body “bottle style” resonators are often employed. Installing a resonator in this area will help prevent that drone frequency from reverberating through the floor and into the passenger cabin. Keeping the resonator further upstream also benefits in cancelling out that drone frequency earlier in the system, preventing it from travelling the full length of your exhaust. Placement will be dependent upon available space as well and is often the most limiting factor for installation. Placement further downstream in the exhaust path will target higher RPM frequencies and overall decibel reduction. This is typical placement for most larger body mufflers. Use your best judgement in identifying where any drone is occurring, in some cases, resonance frequencies can be at their peak further downstream just ahead of the rear axle of the vehicle, this will be a drone emitting from the rear seat area. Target placement in the area where you identify any unwanted frequency is occurring.
• Spacing. When you have a long length of exhaust tubing (more than 5’) without a suppression device, there is an opportunity for exhaust valve pulse wave resonance frequencies to be amplified- much the same way if you were to strike 2 tuning forks that are different lengths- the longer fork will have a larger amplitude. Your exhaust tubing behaves the same way with the pulse wave sent down from the exhaust valve smashing open and closed at incredible speeds- the longer the length without a suppressive device, the more opportunity for a drone frequency to be amplified. For this reason, it is also ideal to try to prevent placement of resonators and or mufflers too close together so they remain most effective across the length of the system.

All Vibrant resonators and mufflers feature a straight through perforated stainless core design to minimize flow disruption of the exhaust. They are not flow directional.
Inlet/outlets are sized by the inside diameter. This means the exhaust tubing will slip inside the resonator/muffler neck and a lap joint weld will be made on each end to install it.
If you have any other questions, please feel free to email us. Thank you for choosing Vibrant, [email protected]

[Jim71]

I have a Gibson single exit kit on order, supposed to ship around the 3rd (tomorrow).I’ll share my experience post install.

[Epsilon Plus]

Put the Vibrant on.

 

Did the trick. Pretty much stock silent inside at very low throttle cruise. No blaring drone through the range, just mellow exhaust tone now. You can hear it has a muffler on it but it canceled out that specific bass frequency that was driving me nuts. Made no change to the exterior tone or volume, still sounds mellow and moderate like it did before.

[Randal Scott]

What's the part number for the Vibrant that you used? 

[Epsilon Plus]

VPE-1144

[Jim71]

I’d like to have had some feedback on the Gibson cat back I have on order but that have yet ship it out .Gibson says they had been waiting on material, then were waiting on fabrication..been weeks.

[Jim71]

Finally got the kit on, sounds great, zero drone.It is for a longbed and does require a cut and relocation of one hanger if you are fitting to a short box.

[64BAwagon]

Jumping back into this thread.   I put an MBRP 4" stainless system on my 2024 3500HD gasser last July. Overall I was happy with it although it was a little louder than I anticipated. It did quiet down a lot at cruising speeds so I was okay with it. We took one short trip in late summer towing the fifth wheel. It was a little louder than I wanted but not bad at cruising speeds of 60-65 in 8th gear (2050 RPM) Of course this was in Indiana and there werent a lot of grades to pull. 

Fast forward to a trip to Florida this winter. After returning I had decided that if I was going to keep the truck I would re-install the stock system because the MBRP became a nuisance in the hills. Once it hits 2400 rpm (common with the gas engine) the noise is too loud, after an entire day it becomes tiring. 

I ended up selling the truck after we got home and included the stock system with the truck so the new owner could decide for themselves if it was right for him. I was very open about my feelings on it.  

Around town I loved it and it sounded great, for towing I would definitely avoid it. 

This was an expensive and time consuming lesson for me. 

Edited April 7, 2025 by 64BAwagon

[Chuck FB]

3 hours ago, 64BAwagon said:

Jumping back into this thread.   I put an MBRP 4" stainless system on my 2024 3500HD gasser last July. Overall I was happy with it although it was a little louder than I anticipated. It did quiet down a lot at cruising speeds so I was okay with it. We took one short trip in late summer towing the fifth wheel. It was a little louder than I wanted but not bad at cruising speeds of 60-65 in 8th gear (2050 RPM) Of course this was in Indiana and there werent a lot of grades to pull. 

Fast forward to a trip to Florida this winter. After returning I had decided that if I was going to keep the truck I would re-install the stock system because the MBRP became a nuisance in the hills. Once it hits 2400 rpm (common with the gas engine) the noise is too loud, after an entire day it becomes tiring. 

I ended up selling the truck after we got home and included the stock system with the truck so the new owner could decide for themselves if it was right for him. I was very open about my feelings on it.  

Around town I loved it and it sounded great, for towing I would definitely avoid it. 

This was an expensive and time consuming lesson for me. 

That seems to be the theme with aftermarket exhaust systems, a more compact muffler and may be really nicely made depending on the company and made from the top grade 304 stainless if its a Borla for example, but the noise is what turns me away from the idea. Of course here in Canada the price seems to be insane as well and certainly if its the genuine GM Borla system for example. I haven't heard it but I have a nephew with a 2013 Ram 3/4 with the 6.4 hemi and he had put a MBRP 4" on and my niece made a comment "I don't like it, its way too loud", and that more than likely is when they would be towing their holiday trailer or when hauling sleds on the deck to the mountains. That all takes power which means throttle input and rpm, none of which is quiet with an inherently loud system. I believe his is a 409 stainless.

 

So which grade of stainless steel is yours, is it the 304 stainless as I don't happen to see a 409 stainless for that model, only the least expensive aluminized steel.

[64BAwagon]

I think it was the 300 series stainless.  doesnt matter now though. 

 

[Chuck FB]

Yes, unfortunately that money has sailed, although your buyer may have liked the fact it had a stainless steel exhaust but sadly add on's rarely pay back well on vehicles.

 

I will admit I am curious though what prompted the sale and purchase of a new truck since they are only one year apart and I've assumed very little change in these two model years ( possibly some minor internal changes ). I don't mean to put you on the spot and you certainly don't have to quantify the new purchase but none the less it has peaked my curiosity !