I know the issue of exhaust bypass on the 986 has had a lot of discussion over the years, but I took a different approach to it and I thought I'd let readers know about it.
I wanted to do it, but was afraid that I might not like the sound; maybe too loud. The question was to use 1", 1 1/4" or 1 1/2" stainless steel tubing. Obviously, making the wrong choice would involve a complete do over! I pondered using the 1 1/2" pipe with electric cutout valves which have a range of adjustment, but the better valves are expensive and would be hard to install because they are rather large and also don't match the diameter of the Boxster exhaust pipes further complicating the installation.
I decided to use a 1" stainless bolt and weld a jam nut onto each side the bypass inlet pipe. I rounded off the bottom of the bolt so it matched the contour of the inside of the pipe. Another jam nut was used to lock in place. The head of the bolt was also cut off. Not that I needed to, but just to clean it up a bit. When fully extend into the pipe I estimate that it creates about a 75% restriction. I can move the bolt up and down increasing and decreasing the the amount of resistance in the 1 1/2" pipe and also the sound. Just count the turns on the bolt so both sides are adjusted equally.
I really like it. Fully open it has a nice throaty sound at idle and lower rpms. At high rpms it really screams. Fully closed it sounds only slight different from stock. In the middle, obviously somewhere in between. I really like the mod overall.
Those that have already done the mod who wanted to back off on it from time to time could easily add this to existing pipes.
I live in Central Florida. If anyone is interested I used Billy at Jiffy Exhaust in Wildwood. He does excellent work and is honest and reasonable. 352 748-5407
In addition, the 2004 Boxster S has removable tips. So I had the bypass pipe welded to the back of the muffler and had the tips sloted in the back so they could still be removed.
