'06 Z06 bimodal mufflers
 

Saw an ad the other day for the new Z06 and they made mention of bimodal mufflers whatever that is. Anyway the text said they are vaccum valve operated so they are quite at idle and loud when you stand on it. In the ad pic you could see the butterfly valves on one side of each exit pipe of the muffler.
http://www.chevrolet.com/i/06/pic/co..._gallery17.jpg
Not that I am old but it drove me nuts when I had two chamber Flowmasters on my Camaro and had to turn it off in the drivethru's. Anybody know anything about these or know of an aftermarket variant?

Mike

haha how about some cutouts and quiet ass mufflers?

Thats what im doing as soon as i find a company that builds a reliable cutout

what if you were to take a elec cut out, and hook it to a vacuum relay, the cut out would need some air holes in it, but i would think that at idle you could seriously cut the noise down.

I once knew a guy (dead now) that had a pair on his C4 vette, they worked very well. At idle it sounded stock and anything more than about 50% throttle opened them right up. He was a true best of the best kind of guy, dyno tested and drag strip tested everything, even kept his laptop in the car for evaluations of runs. They were about the only thing on the car that remained for any length of time.

So is there a vacuum line that runs all the way to the back of the car, or is there a vacuum operated switch in the engine compartment that sends a signal to a solenoid back aft?

If you look to the left of the passenger side muffler it appears there is a vacuum container with a line going off it. The mufflers work all the time no turning them on or off. Although, it didn't take long before people figured out there was a fuse you could remove to make them stay wide open.

From the GM website:

http://www.chevrolet.com/i/06/pic/co...06_exhaust.jpg

Z06 Exhaust System
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The three-inch-diameter exhaust system features a bimodal shutoff, which reduces noise output at idle and during moderate driving, while providing reduced back pressure at speed for race car-like performance. A vacuum-operated valve varies the exhaust note and volume according to engine load. At wide-open throttle, the sound emanating from the four trumpet-shaped exhaust outlets at the rear of the car is nothing short of sensational.



Hmmm....wheels turning.

There was a PT style AMX that had something close to this. I don't know if I still have the mag, but I'll look.

Shiny Side Up!
Bill
'72 442 "Inamorata"

Ferrari has employed this for many years too, not only for noise control but to vary backpressure and pressure waves for scavenging via servomotors.

And yes, the guy with the trick AMX has this too, although he uses them as bypass valves to run the exhaust through smaller pipes while cruising to keep the noise levels down.

I believe "Power Effects" was the vendor making variable mufflers for the C4 crowd.

I think this would be the easiest way to go.

You could also hook the cut out to only open at WOT, with a microswitch.