Cause they are silly.

 

Thats pretty interesting! Cant you do basically the same thing with an electric cutout?

 

I'd assume if u put a hole in the butterfly so its not a completely closed thing it should work.

 

yes but all other cutouts I found (mech, elec) were pricier than the entire VT mufler.

 

I've been wanting to build my own muffler with one of these flaps in it, I think i am going to use a resonator though and put the flap inside it. That way when the flap is closed it causes the gas to go through the packing in the resonator, instead of just blocking most of the flow.

 

If you're willing to go that far why not just run a cutout before the muffler?

 

Because a cutout has to seal 100% and that would be too hard for me to build. That and i'm really cheap, even the cable style cutouts (which don't seal well) are nearly 60 dollars. For a few pieces of metal and cutting and welding the resonator I already own i can make my own... why not?

 

Get a 10 bucks throttle body from an old civic or something. The mount is easy to make if u have a welder.

 

Not sure an aluminum throttle body would hold up at the end of the downpipe. Not to mention it still probably would not seal 100% although it would be really close.

 

Remember that these restrictors work best at quieting the drone/thrum when installed at the end of the exhaust. This way the exhaust pulses have the entire volume of the exhaust to pressurize/de-pressurize.

 

EVOs, F430s, and E46 BMW afaik have them.

EVO muffler cutaway: Flapper is in the upper left. The arrows show the flow while flapper is closed. When it opens it bypasses the circuitous route.

 

The popular quiet 3" muffler seems to be the 22x5x11 Magnaflow, but I like the flapper idea. All the Dynomax VT Mufflers are of the smaller variety except for the 17963:


If a Dynomax 17963 were to be installed on a miata I would envision that the dual 2.5" outlets would have gradual 90° turndowns, rotated 45° to the rear. The flapper may not last a long time, but these mufflers are relatively cheap if they need replacement in a few years.

Pro's?
Con's?

 

Don't use turndown tips that point to the ground. The noise gets reflected from the ground up to the car. Ask me how I know...

 

So are you guys figuring out how to get the brown note out of the exhaust, cause road trips kinda suck with a brown note! just saying.

 

How do you know?

 

LOL I'll bite whether you're joking or not... what else, I tried it when I upgraded my old 2.5" muffler to a larger one, was aghast at the noise ... complained bitterly to Magnaflow, then realized it was the temporar turn down...(was waiting for a proper tip to come in)

 

I am so pissed off that they dont sell something like this seperately from the muffler, for say, 50-60. I mean its simple as hell, and obviously effective, why hasn't someone already started mass producing these thingamabobs?

 

Then you wouldn't have to buy their muffler...

 

Duh...

 

My research on these VT mufflers hasn't shown much promise. Apparently they are really bad for boxer engines (boo for my Forester) and cars with cams. Apparently the flapper and rattle at idle and other situations. Also, it seems the flapper starts to wear over time and loses some performance, for the Evo guys it was after ~ 1 year.

Honestly, I wish somebody would run with this idea but do a better job engineering it. The Dynomax VT muffler is pretty affordable but it seems to have some serious flaws. Personally I would rather pay $200 for the muffler if it worked 100% as advertised. Versus paying ~$100 for a muffler that sort of works but also rattles like hell at idle...