Aevus
08-11-2021, 11:24 AM
Hey guys, I need to share my experience since I didnt take the usual bolt-on route Borla or Corsa catback... And also I have a solid background in acoustic.
Just to clear things up from the start, my goal was not to achieve the loudest possible exhaust system but to have the less restriction and the less exhaust reversion possible, in order to optimize the scavenging effect at high rpm. I'm working on an engine that will peak around 6,800-7,000rpm.
So if your goal is to keep the maximum possible low-end torque, you might want to stick with the usual 3 inches diameter.
My baseline was:
- stock headers
- stock cats (2 each sides)
- stock crossovers (gen 3)
- stock resonator/muffler delete
Basically, the somewhat very restrictive stock cats were acting as the muffler. Helped by the crossovers, most probably. Nice overall sound, perfect if you are on a tight budget. Not loud but not too quiet.
Next was:
- M&M headers
- High flow Magnaflow 3'' cat (1 each sides)
- Vibrant race muffler 3.5'' (model 1796)
- Direct 3.5'' exit
As expected, the thing is loud. We probably can say ''crazy loud''. Didn't soundtest at WOT but I wouldnt be surprised if the thing would make 140db SPL at 1 meter distance, if not more. In-cabin at idle, it shows on my app a 102db rating and even though the app may not be perfectly accurate, it makes sense. Now, the problem is not really the high sound levels, it's the frequencies....
48838
As you can see, it's all low and very low frequencies. That's what is commonly called ''DRONE'' noises. The problem is: the Viper engine is huge. Therefore it produces lots of low frequencies. Pretty much like big diesel trucks. I sure can feel in the cabin ''subwoofer'' kind of frequencies, which means 20-30hz. That's very low and very annoying. I did a 3 hours roadtrip and the constant low-freq rumble was deafening, so I had to keep the engine in higher rpms to change the resonant frequency...
Needless to say that is not good. It's a real head-turner, everybody smiles hearing it on idle because it sounds like a Harley-Davidson, but you probably don't want to live with that. And since low-frequencies can be heard from longer distances, your neighbors will hate you.
So basically, the SOLUTION is not a muffler but a resonator. You want to suppress those annoying lower frequencies. And since the engine is huge and the frequencies very low, you need a big and long resonator that will be truly effective.
So I ended up with a Diamond Eye Performance 4'' resonator. 24 inches total lenght, installed after the Vibrant muffler, so its aligned with the seats, just before the exhaust exit. It's a resonator usually used for trucks but it shouldnt stop you from using it on a Viper. If you want to get rid of the annoying noises but don't want a restrictive muffler, the options are very limited.
Soon I will post a video that shows the result, along with a new audio RTA screenshot to show the difference.
Just to clear things up from the start, my goal was not to achieve the loudest possible exhaust system but to have the less restriction and the less exhaust reversion possible, in order to optimize the scavenging effect at high rpm. I'm working on an engine that will peak around 6,800-7,000rpm.
So if your goal is to keep the maximum possible low-end torque, you might want to stick with the usual 3 inches diameter.
My baseline was:
- stock headers
- stock cats (2 each sides)
- stock crossovers (gen 3)
- stock resonator/muffler delete
Basically, the somewhat very restrictive stock cats were acting as the muffler. Helped by the crossovers, most probably. Nice overall sound, perfect if you are on a tight budget. Not loud but not too quiet.
Next was:
- M&M headers
- High flow Magnaflow 3'' cat (1 each sides)
- Vibrant race muffler 3.5'' (model 1796)
- Direct 3.5'' exit
As expected, the thing is loud. We probably can say ''crazy loud''. Didn't soundtest at WOT but I wouldnt be surprised if the thing would make 140db SPL at 1 meter distance, if not more. In-cabin at idle, it shows on my app a 102db rating and even though the app may not be perfectly accurate, it makes sense. Now, the problem is not really the high sound levels, it's the frequencies....
48838
As you can see, it's all low and very low frequencies. That's what is commonly called ''DRONE'' noises. The problem is: the Viper engine is huge. Therefore it produces lots of low frequencies. Pretty much like big diesel trucks. I sure can feel in the cabin ''subwoofer'' kind of frequencies, which means 20-30hz. That's very low and very annoying. I did a 3 hours roadtrip and the constant low-freq rumble was deafening, so I had to keep the engine in higher rpms to change the resonant frequency...
Needless to say that is not good. It's a real head-turner, everybody smiles hearing it on idle because it sounds like a Harley-Davidson, but you probably don't want to live with that. And since low-frequencies can be heard from longer distances, your neighbors will hate you.
So basically, the SOLUTION is not a muffler but a resonator. You want to suppress those annoying lower frequencies. And since the engine is huge and the frequencies very low, you need a big and long resonator that will be truly effective.
So I ended up with a Diamond Eye Performance 4'' resonator. 24 inches total lenght, installed after the Vibrant muffler, so its aligned with the seats, just before the exhaust exit. It's a resonator usually used for trucks but it shouldnt stop you from using it on a Viper. If you want to get rid of the annoying noises but don't want a restrictive muffler, the options are very limited.
Soon I will post a video that shows the result, along with a new audio RTA screenshot to show the difference.