Opening up a muffler? Is it even a good idea?

[fields_mj]

Hello fields_mj , did you calculate the area of the pipe and the area of the exhaust hood (little cover on the outside) ?

Nope. I have read through many of the threads pertaining to the exhaust port dimensions, and I believe they are absolutely correct. That said, the general result is that you can basically double the area and be relatively close to nominal. There are many different ways of doubling the area, and I wasn't really looking for another project to take on. I just knew that with a heavy blade on the trimmer, it was taking longer than I wanted to get the blade up to speed. If it had ended up being too much, I would have either added a screen, or covered part of the hole with a small piece of steel or sheet metal secured in place with a machine screw or two. I decided that I'd start with a hole that was roughly the size of the ID of the existing pipe. It had the desired effect so I never revisited the issue.

 

[fields_mj]

While that's not the turbocharger's intended purpose, the exhaust gases do pass through them and because of that it's not to hard to understand how/why the turbo would in effect lower the S.P.L. produced by the engine.

^^^^ This. The purpose of a turbo is to harness energy from the exhaust gasses. The result is that the exhaust gasses are slower and/or cooler coming out of the turbo which is also what a muffler does. Don't get me wrong. If you take the muffler off of a turbo charged engine, it will be very obvious that it's missing a muffler.

 

[fields_mj]

My audiologist tells me that as good as ear plugs are, muffs are better. Somehow the noise still goes into the ear around the outside of the ear itself into the ear canal.
Her suggestion is to wear both. But in doing so, you don't get double insulation. It's more like the highest number, added to one half of the lower one.
Example...my inside plugs give me 32 db reduction, over the head muffs 27, which will equal about 46 db total deduction. I always wear both when using the chainsaw and tractors, if it's for any length of time. Try to save what's left.
Your mileage may vary of course

Sound is a type of energy, and energy normally dissipates logarithmically. Applying that to ear pro, going from 20db to 30 db of reduction would require blocking out 10 times more of the sound. That's the main reason you can't just add the numbers together.

I generally only wear one type of ear pro at a time. I've found that wearing both muffs and plugs makes it almost impossible for me to notice anything going on around me. The exception to that is when I'm training or competing on a firing range. Then I prefer using both. If I'm on an indoor range, I consider it mandatory to have both on.

 

[Sloughfoot]

While that's not the turbocharger's intended purpose, the exhaust gases do pass through them and because of that it's not to hard to understand how/why the turbo would in effect lower the S.P.L. produced by the engine.

Suzuki agrees

https://drive.suzuki.co.nz/blog/tur...t=As the air in a,a quieter and smoother ride.

 

[scottr]

Nope. I have read through many of the threads pertaining to the exhaust port dimensions, and I believe they are absolutely correct. That said, the general result is that you can basically double the area and be relatively close to nominal. There are many different ways of doubling the area, and I wasn't really looking for another project to take on. I just knew that with a heavy blade on the trimmer, it was taking longer than I wanted to get the blade up to speed. If it had ended up being too much, I would have either added a screen, or covered part of the hole with a small piece of steel or sheet metal secured in place with a machine screw or two. I decided that I'd start with a hole that was roughly the size of the ID of the existing pipe. It had the desired effect so I never revisited the issue.

Did the addition of the 3/8" hole create a snap , crackle , pop sound ?

 

[SCMtnHaul]

At least in the case of an International/Navistar 7.3 IDI a turbo really quiets the engine sound. Maybe it doesn't "muffle" the sound but it is much quieter compared to a non-turbo 7.3 IDI. I've driven and been around plenty of them and a non-turbo with factory muffler is louder than a turbo with factory muffler.

 

[fields_mj]

At least in the case of an International/Navistar 7.3 IDI a turbo really quiets the engine sound. Maybe it doesn't "muffle" the sound but it is much quieter compared to a non-turbo 7.3 IDI. I've driven and been around plenty of them and a non-turbo with factory muffler is louder than a turbo with factory muffler.

Mine didn't have a turbo and it had a noticeable growl. I can see where a turbo would have made a noticeable change in the exhaust signature.

 

[fields_mj]

Did the addition of the 3/8" hole create a snap , crackle , pop sound ?

No. It was a little louder obviously, and pitch at WOT increased slightly, but otherwise it was unchanged.