'06 Z06 Bimodal mufflers

[MuscleRodz]

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.

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

[Ralph LoGrasso]

Mike,

I've hard that they open up at around 3,000rpms. I'm not sure if it's exactly at 3,000rpms or if throttle position has anything to do with it. I'd assume it does, but you know how assumptions go.

[protour_chevelle]

Ya, they kick open around 3200rpm(yet another range lol). I called it Vtec when I first heard it haha.

-Matt

[Tom Welch]

I've seen a cut away of one of these mufflers and the idea seems simple enough, a valve that is spring loaded opens as exhaust pressure rises to allow for more flow, apparently several manufacturers are using it. There are no electronics or anything to deal with, makes the muffler look odd though.

[Damn True]

It's my understanding that there is an electric servo that operates the valve that is driven by a signal from the ECU. The determiners for opening are certain vacuum levels and/or WOT.

[CamaroAJ]

all close, the vacuum holds the valves closed untill the solenoid is powered down then the valves open, the designes at GM put a seperate fuse for the solenoid and it you take it out its open valves all the time and no check engine light.