Exhaust Bypass Valve Operation

mine isnt working after changing the headers...What is the best way to trouble shoot it?

 

Taz's post number 17 of this thread shows diagram of this system. First be sure that all the vacuum lines are where they are supposed to be. If you need to go farther, check the condition of the lines for vacuum leaks.
Would normally guess that the problem is likely at the rear of the car however, since you just had work done at the front, check that area first. Think Taz posted a relevant pic from WSM of the rear area in his first few post in this thread.
Will add that there is no reason to wire these open mentioned in the begining of this thread. A simple reroute of two vacuum lines at the rear of the car will accomplish keeping the bypass valves open all the time.
Bill
FL

 

I love these threads. Not sure about this "mod".

So Challenge cars do not run this correct? Because they are always at higher RPM?

 

No valves on Challenge cars.

 

I know this is an old thread, but thought I'd add my experience. I did this mod on my 550 last week, took 15 mins including jacking up the car. After 1 week, I undid the mod. The exhaust note was definitely louder at idle, but that's about it, under acceleration, hard and moderate, no real change in volume or sound. After a week the extra volume at idle only was starting to bug me, it sounded more like a rusted out muffler from inside the car when sitting at a stop light. With the windows open it sounded ok, but with the windows closed it was just a loud droning sound at idle. I think being relatively quiet at idle is part of what makes these cars classy. I would like to find a better sound when accelerating and I already know the options for that, but this is an easy and free mod worth trying if you like to tinker.

 

Best option is to get one of the kits for selecting open or ECU controlled for the bypass valves. Capristo and Steve Bisel both sell kits for that. At WOT on a 550 or above ~2700 rpm and 64% throttle on a 575M, there is no difference in sound because the valves are open anyway.