[Simon H]

Originally Posted by AGS

I'm by no means an expert, but I spent some time playing around with the exhaust valves the other day. Based on my visual inspection, the only thing leading to the actuator that controls the valve is the vacuum line. I had read some comments in this and other threads that the valves open when the cats warm up or Sport+ mode is selected on the throttle control. Again, I may be wrong, but I do not think either of these is correct since there is no electronic control of the valves - it appears as if the valves can only be opened by sufficient pressure built up in the vacuum line. From moving them by hand I can tell you it's a fairly stiff spring, so a lot of pressure will be necessary - likely once the engine is above something in the 5,000 to 6,000 RPM range. I looked at a schematic of the exhaust on realOEM.com and there is an in-line electronic value farther up the vacuum tube which may control whether or not the exhaust valve is "active" based on certain settings or other conditions, but I do not think it can actually control the valve itself.

Thanks AGS.