The first spring project for the Z was trying to quiet it down as much as possible with the current test pipes/Invidia Gemini exhaust setup. My local autocross site in Devens, MA has a stricter sound requirement now, which I almost exceeded last year. Also, I was hoping to kill off the drone introduced by the replacement resonators that I recently had welded into my Y pipes.
The Gemini has some straight sections where I was able to slip in 2x Vibrant bottle resonator (PN 1792) between the flange and hangers. The annoying bit is that the Gemini uses 60mm (2.36”) OD pipe, but the vibrant resonator are intended to slip over 2.5” pipe. Therefore, I needed to make some adapters from small sections of 2.5” OD pipe, which luckily slips nicely over 60mm pipe. I cut reliefs in the adapters and the resonators to allow the clamps to do their job and squeeze it all together.
These new Vibrant resonators killed all drone and tamed the exhaust just a bit to where the car is much more enjoyable to drive. It still opens up nicely and is certainly still loud when I get on it.
Additionally, as another safety measure for autocross events, I quickly fabbed up some 90deg turn downs from 2.5” exhaust bends from autozone. These are good for a couple dB of “quieting” according to the autocross veterans at Devens. The non-expanded ends of these 90deg bends slip nicely over the 60mm pipe. Same as the resonators, I cut reliefs in the pipe to allow for clamping. As a final measure to make sure I didn’t exceed the sound limit, I clamped chicken wire and stainless mesh to the ends of the exhaust bends (sorry no pics of this). No one bothered me about sound during my couple of runs at my first event of the year on 5/26, so I guess all of this was successful!
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