Muffler help please

Kuuups · January 25, 2020

I got a black widow muffler 3” in and 3” dual out and the guys at the muffler shop are saying that it’s gonna kill my low end torque. If I still decide to install it would the truck become sluggish during take off? I’m purchasing a ported manifold and a bigger throttle body would that help recover whatever low end torque I lose? I just need some insight for the muffler is it worth going through with it or should I just return it and get one with 2.5” dual out??? Anything helps...

CamGTP · January 25, 2020

Nothing is going to change with a muffler swap, nothing. You could chop it out and run straight pipes, it wouldn't make a difference. There is going to be no gain or loss in low end torque from a muffler swap.

Tell them they don't understand exhaust flow and how reality works. All the information is out there but they're just too thick headed.

You'll gain some with the manifold/throttle body but that's only if the tune is spot on. Whoever tunes it needs to know what they are doing.

Kuuups · January 25, 2020

1 hour ago, CamGTP said:

Nothing is going to change with a muffler swap, nothing. You could chop it out and run straight pipes, it wouldn't make a difference. There is going to be no gain or loss in low end torque from a muffler swap.

Tell them they don't understand exhaust flow and how reality works. All the information is out there but they're just too thick headed.

You'll gain some with the manifold/throttle body but that's only if the tune is spot on. Whoever tunes it needs to know what they are doing.

Thanks for the reply. Kinda got worried because they were saying I’m gonna lose a lot of low end with the 3” dual out.

Mileguru · January 26, 2020

I have a 2017 Sierra SLT crew cab 6.2L with a Magnuson TVS1900 supercharger, methanol, and a tune (obviously). I swapped my muffler to a Magnaflow 12909. I did notice a slight decrease in low end torque as I drove it around after the swap, but got used to it after a few days. The decline was nothing significant, but I could feel a slight lag compared to what it used to be - very slight.

By the way, where do you live? I used to live in Kapahulu for a long time...stuck in Los Angeles now =(

DenaliX14 · January 26, 2020

You’re not going to notice. Are you going to have it tuned?

KARNUT · January 26, 2020

No

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Kuuups · January 27, 2020

On 1/25/2020 at 3:15 PM, Mileguru said:

I have a 2017 Sierra SLT crew cab 6.2L with a Magnuson TVS1900 supercharger, methanol, and a tune (obviously). I swapped my muffler to a Magnaflow 12909. I did notice a slight decrease in low end torque as I drove it around after the swap, but got used to it after a few days. The decline was nothing significant, but I could feel a slight lag compared to what it used to be - very slight.

By the way, where do you live? I used to live in Kapahulu for a long time...stuck in Los Angeles now =(

Suck build! I live in ewa beach now just got my own place haha but before that I lived in Waimānalo and kapolei. Nice to see some Hawaii braddahs on the forums lol

Kuuups · January 27, 2020

23 hours ago, DenaliX14 said:

You’re not going to notice. Are you going to have it tuned?

Probably in the future. I want to cam my truck too pretty soon

Mileguru · January 27, 2020

1 hour ago, Kuuups said:

Suck build! I live in ewa beach now just got my own place haha but before that I lived in Waimānalo and kapolei. Nice to see some Hawaii braddahs on the forums lol

Congrats on your new place. I loved Waimanalo...Sweet Home Waimanalo - Bu La'ia. But now I've got Waimanalo Blues (Pure Heart) that I'm gone. Check out those two songs if you don't already know them

I used to live in Kaneohe before Kapahulu. Are you military?

Kuuups · January 27, 2020

40 minutes ago, Mileguru said:

Congrats on your new place. I loved Waimanalo...Sweet Home Waimanalo - Bu La'ia. But now I've got Waimanalo Blues (Pure Heart) that I'm gone. Check out those two songs if you don't already know them

I used to live in Kaneohe before Kapahulu. Are you military?

Those are the jams ! And no not military just a Regular local haha

Kuuups · February 5, 2020

On 1/25/2020 at 4:23 PM, DenaliX14 said:

You’re not going to notice. Are you going to have it tuned?

Yes after I do more mods

00pooterSS · February 6, 2020

If you still have stock manifolds and cats the muffler wont make you lose low end. Headers is what MIGHT make you lose a little low end, if you go to larger primaries than needed for the setup.

You lose low end when you lose exhaust velocity that pulls fresh air in the cylinder during overlap, that is called scavenging. Which I don't think the stock cams even have overlap. But the scavenging effect still helps, but you wont lose scavenging from just a muffler swap, if anything you'll gain.

You may lose a tiny bit of low end if you go to large tube headers, and large exhaust. But lol no you won't lose from a muffler.

When I had stock manifolds and cats, I swapped to a maganaflow straight through muffler and cut out the flapper valve. I gained a couple mpg, I gained 3mph at my test spot that is approx 1000-1100 feet ( I always test my mph there after making a change) and it felt better everywhere.

In short. Have the muffler done and ignore those guys, they "know just enough to be dangerous"

My tuner has also said several customers have called them and said they gained mpg by swapping the cat back, which you'll be doing a similar thing by swapping the muffler. You're gonna actually pick up everywhere, not lose.

As for your manifold and throttle body, those are more likely to kill a tiny bit of low end than the muffler.

Edited February 6, 2020 by 00pooterSS

00pooterSS · February 6, 2020

On 1/25/2020 at 7:15 PM, Mileguru said:

I have a 2017 Sierra SLT crew cab 6.2L with a Magnuson TVS1900 supercharger, methanol, and a tune (obviously). I swapped my muffler to a Magnaflow 12909. I did notice a slight decrease in low end torque as I drove it around after the swap, but got used to it after a few days. The decline was nothing significant, but I could feel a slight lag compared to what it used to be - very slight.

By the way, where do you live? I used to live in Kapahulu for a long time...stuck in Los Angeles now =(

Same happened to me when I put headers and 3.5" catback on my truck. But when I got the tune corrected all the power came back plus some. The problem wasn't that I made the exhaust flow better, it was that the tune needed to be corrected for the additional flow. Likely the same issue with yours. Open up flow, it gets a little lean, little lean feels a little less powerful.

Kuuups · February 12, 2020

On 2/6/2020 at 7:34 AM, 00pooterSS said:

If you still have stock manifolds and cats the muffler wont make you lose low end. Headers is what MIGHT make you lose a little low end, if you go to larger primaries than needed for the setup.

You lose low end when you lose exhaust velocity that pulls fresh air in the cylinder during overlap, that is called scavenging. Which I don't think the stock cams even have overlap. But the scavenging effect still helps, but you wont lose scavenging from just a muffler swap, if anything you'll gain.

You may lose a tiny bit of low end if you go to large tube headers, and large exhaust. But lol no you won't lose from a muffler.

When I had stock manifolds and cats, I swapped to a maganaflow straight through muffler and cut out the flapper valve. I gained a couple mpg, I gained 3mph at my test spot that is approx 1000-1100 feet ( I always test my mph there after making a change) and it felt better everywhere.

In short. Have the muffler done and ignore those guys, they "know just enough to be dangerous"

My tuner has also said several customers have called them and said they gained mpg by swapping the cat back, which you'll be doing a similar thing by swapping the muffler. You're gonna actually pick up everywhere, not lose.

As for your manifold and throttle body, those are more likely to kill a tiny bit of low end than the muffler.