What is an Exhaust Valve Actuator? What does it do? How does it work?

A valve actuator is the mechanism for opening and closing a valve. Manually operated valves require someone in attendance to adjust them using a direct or geared mechanism attached to the valve stem. Power-operated actuators, using gas pressure, hydraulic pressure or electricity, allow a valve to be adjusted remotely, or allow rapid operation of large valves. Power-operated valve actuators may be the final elements of an automatic control loop which automatically regulates some flow, level or other process. Actuators may be only to open and close the valve, or may allow intermediate positioning; some valve actuators include switches or other ways to remotely indicate the position of the valve.

The following is a general series of events when monitoring the response of an exhaust valve actuator in an exhaust system:

1. The exhaust valve is closed between idle and nearly 3000 rpm, muting exhaust noise under most normal driving conditions. So you don't hear the loud engine sound until you get on the gas and exceed 3000 rpm.

2. At cruising speeds it reduces "drone". However, if you like to hear exhaust sound, the engine rumble at low rpm actually becomes audible with the valve open (different but more natural than intake sound piped into the cabin, for example).

3. When applying moderate gas at low rpm (when the valve is closed), it feels like throttle response is delayed while the ECU hesitates to determine power output and downshift gear. This is most noticeable at medium cruising speeds under 2500 rpm in gears 3-6 (possibly in an attempt to make the car feels less "jumpy"). There is faster turbo response down low when the valve is in the open position, and the initial hesitation seems to be nearly eliminated. However, driveability becomes a little more linear with reduced initial hesitation after a moderate throttle input, especially when the transmission downshifts in auto mode.

4. With the valve open (actuator disconnected) there is an even bigger difference in exhaust sound between normal mode and sport mode. There is even louder exhaust sound at cruising speeds, more crackles and burbles (primarily idle to 3000 rpm). Thus, this valve does not control sport or sport + mode exhaust function, it is something internal (either programming or additional valves within the exhaust pipes or mufflers).

5. With the valve open, all of the exhaust noises are more audible, including the engine noise as well as the engine whistle. So if you don't like the engine noises this is probably something to leave alone.

6. There have been different experiences with leaving the actuator unplugged for extended periods of time. Some have noticed the valve stops working when you plug it back in after months or a year.