Quote:
Originally Posted by AGS
I spent some time playing around with the exhaust valves today. First I did a 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. 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.
Next I started up the car an opened and closed the valves by hand. There is a slight increase / improvement in sound at idle with the valves open, but nothing dramatic. The exhaust seems to have a slightly deeper tone with the valves open.
The last thing I did was temporarily lock the valves open using some heavy duty twist ties and went for a short drive. As with my observation at idle, there is a slight increase in the sound level and a slightly deeper tone to the exhaust - it is not dramatically louder driving with the valves locked open. Another important lesson learned - for my experiment I did not touch the vacuum lines and there was no impact to performance. It seems as long as the vacuum lines are still connected to the actuator, back pressure is maintained and there is no loss in power as ColdList experienced when his exhaust installed just left the vacuum lines unplugged. The twist ties I used for this test were not appropriate to leave on permanently, so my next step will be getting the proper materials to lock the valves open on a long-term basis.
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Good information thanks, was there a lot of pressure needed to "pull these sprung flaps to the open position"?.