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Old Feb 14, 2024 | 01:19 PM
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Default Catless Setup LSA

Hey everyone, first post on the forum so bare with me if this ain't the right spot for it. I'm having my obs Sierra swapped with a built LSA(550-600whp depending on the two pulleys) and need help picking out the right exhaust. First things first, I'm in CA and will be "smogging" under the table. So the legality of emissions doesn't matter here and to make the most power, I will be catless and long tubed. This will be extremely loud so I’m looking for a quiet system that flows well. From my research, the Dynomax super turbo is the quietest while still flowing over 500cfm so I want to pair that muffler with a vibrant ultra-quiet resonator.

Talking with the shop they were skeptical with dynomax’s quality and recommended corsa pro (their quiet one) but I still feel like even the corsa pro will be way too loud. I know I may have to compromise somewhere so I appreciate any insight yall may have.
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Old Feb 14, 2024 | 02:17 PM
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factory exhaust with a boost or TPS activated cutout before the muffler. only way you will keep it quiet and not lose performance at WOT
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Old Feb 14, 2024 | 02:37 PM
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Originally Posted by Ryans99ls1
factory exhaust with a boost or TPS activated cutout before the muffler. only way you will keep it quiet and not lose performance at WOT
Holy hell I forgot about cutouts being vacuum/boost activated, thank you I appreciate that.
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Old Feb 14, 2024 | 02:47 PM
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The good news is that you have plenty of room under a truck to get creative with the exhaust. I've had a couple of TVS supercharged trucks and am pretty particular about how my exhaust sounds. I want it quiet at cruise and loud as it wants to be at WOT.

If I put another one together, I'd go with the Corsa's by themselves and see how you like it. My last supercharged truck had long tubes, no cats, and Magnaflow mufflers to start with. I ran it like that for a little while and got tired of the constant drone at cruise. It never shut up. Added some short resonators behind the Magnaflows and it was perfect. Mellow around town, quiet at cruise, and pretty damn loud at full tilt.

You want a muffler you can see through. I could see through the Magnaflows and Corsa's that I have used. Chambered (like Flowmasters) mufflers are restrictive. With Flowmasters, I had 4psi of backpressure measured at the X pipe between the headers and the mufflers. That raises boost pressure (and intake air temps) and costs you power compared to a 0 back pressure exhaust. The Magnaflows had 0 back pressure. I'm sure the Corsa's would show similar as they are an even a more straight thru design than the Magnaflows.
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Old Feb 14, 2024 | 04:32 PM
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Originally Posted by old motorhead
The good news is that you have plenty of room under a truck to get creative with the exhaust. I've had a couple of TVS supercharged trucks and am pretty particular about how my exhaust sounds. I want it quiet at cruise and loud as it wants to be at WOT.

If I put another one together, I'd go with the Corsa's by themselves and see how you like it. My last supercharged truck had long tubes, no cats, and Magnaflow mufflers to start with. I ran it like that for a little while and got tired of the constant drone at cruise. It never shut up. Added some short resonators behind the Magnaflows and it was perfect. Mellow around town, quiet at cruise, and pretty damn loud at full tilt.

You want a muffler you can see through. I could see through the Magnaflows and Corsa's that I have used. Chambered (like Flowmasters) mufflers are restrictive. With Flowmasters, I had 4psi of backpressure measured at the X pipe between the headers and the mufflers. That raises boost pressure (and intake air temps) and costs you power compared to a 0 back pressure exhaust. The Magnaflows had 0 back pressure. I'm sure the Corsa's would show similar as they are an even a more straight thru design than the Magnaflows.
hey thanks for the response! I agree, flowmasters are too restrictive not to mention they have that “hollow/tin” sound from the chamber. Thanks for the advice, I was also thinking about running the magnaflow with the vibrant ultra quiet. When your trucks idle, is it noticeable from 5-10 feet away or do you have to get up close to hear it?
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Old Feb 15, 2024 | 12:51 PM
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Originally Posted by LSAC1500
hey thanks for the response! I agree, flowmasters are too restrictive not to mention they have that “hollow/tin” sound from the chamber. Thanks for the advice, I was also thinking about running the magnaflow with the vibrant ultra quiet. When your trucks idle, is it noticeable from 5-10 feet away or do you have to get up close to hear it?
I had a mild blower cam in both of them. You could tell they weren't stock from more than a few feet away.
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