This is a review of a cheap valved exhaust muffler from Aliexpress. The exhaust was tested on a VAG 1.8T engine.
Should You Buy One?
The short version is this.
There appear to be two types of valved exhaust mufflers available. One where there is a single small hole leading into the muffler body. And another where there are multiple holes leading into the muffler body.
You want the muffler with multiple holes because it’s less restrictive when the valve is closed. You can use it more/all of the time with the valve closed (quiet) and not have it effect engine power.
Some links to videos which use these less/non restrictive valved exhausts here and here. Maybe its possible to tell which is which from the pattern on the muffler body?
The muffler with the single hole (the one I have) is restrictive even at idle. In reality I think you’d have to drive around with the valve open most of the time which i think defeats the point.
Who Should Buy A Valved Muffler?
Let me break the answer in half, one answer for the restrictive type and one for the non-restrictive type.
I think the restrictive type is suitable for no one, unless they can open the valve gradually. (These exhausts are sold with vacuum trigger which means they are either open or closed).
For the non-restrictive type I think it is suitable for people who want more volume from their exhaust system even when the valves are closed. And they want a loud exhaust at the push of a button.
Do You Need Switching?
If you just want to make your existing exhaust louder I think it is cheaper and easier just to buy a y-piece with the valve and switch and weld it to your existing exhaust.
If you want to make your exhaust quieter, I think fitting an extra silencer or a bigger silencer in the exhaust is easier and more effective than a valved muffler.