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Discussion Starter #1
Hello - I am a new member and hope I can find some help. I recently bought a 06 EX-L w/ RES and no NAV. I upgraded the rear mid panel speakers with some nice polks and added a sub to the rear via speaker line level inputs to the amp. All works well, but when I drive I am getting intermittant woofer flutter based on the rpm of the engine(mostly when coasting) when i accelerate it goes away. tried multiple ground points and line out put converters....no luck. Anyone have any ideas. I am fresh out. Thank you
 

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Sounds like you might be hearing the ANC (Active Noise Control) emitted from the sub, when the VCM (Variable Cylinder Management) shuts down 3 of the cylinders.

Here is a description of ANC and VCM from Yahoo Autos:

Variable Cylinder Management uses Honda’s i-VTEC (intelligent Variable valve Timing and lift Electronic Control) to stop the valves on three cylinders from opening. The i-VTEC engine has overhead camshafts with a pivoting cam follower riding on the camshafts. Two rocker arms on either side of the cam follower are interlocked with the cam follower, so as the follower moves the rocker arms open the valves. To deactivate valves, hydraulic oil pressure is supplied by a computer-controlled solenoid to move a pin that interlocks the rockers and cam follower. As this occurs, the cam follower is still free to move as the camshaft rotates, but the rocker arms are no longer connected to it. This pin moves back and forth, linking or unlinking the rocker arms to control valve operation. Even though parts are rotating at several hundred cycles per minute, they can be linked or unlinked in a fraction of a second to switch from six to three cylinders, or back to six cylinders again.

The VCM system stops and starts the opening of intake and exhaust valves of the three cylinders in the rear bank on this engine, based on computer analysis of throttle opening, vehicle and engine speed, and gearing. With zero valve lift, the cylinders are sealed, fuel is not injected, and pumping losses are thus reduced by as much as 65 percent.

Running a six-cylinder engine on only three cylinders represented a challenge to Honda engineers. VCM required several advanced technologies to mask the vibration inherent in three cylinder engines with their more widely-spaced power pulses. To deal with this, the "drive-by-wire" electronic throttle computer assures that power neither increases or decreases during the switchover. Also, an Active Noise Control system cancels out excessive engine noise using a microphone to detect the noise, and then generating a signal 180 degrees out of phase to cancel out the noise. These canceling sound waves are emitted from the front and rear speakers during three-cylinder operation, idling, and at-start running. The ANC system is not needed when running on all six cylinders. Finally, two active control engine mounts, one in front of the engine and another behind, are controlled by the engine computer, which uses solenoids to damp fluid movement in the mounts. During three-cylinder operation, the computer monitors changes in crankshaft rotation rpms and sends this information to the mounts, which then compress or extend an actuator to dampen the engine vibration.
 

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Discussion Starter #3
Thanks a million Curiousgeorge2! I just bought the van and that is exactly what is happening through my sub. I read there is a way on the radio to turn ANC off. I hope this works. I see that some people are cutting wires under the parking brake as well to stop this. I appreciate the feedback. It is appreciated.
 
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