by fbirch » Tue Feb 21, 2017 4:58 pm
If you think you may later want to add a performance header and mid pipe, go with the Q. Based on a first hand drive of an NC Miata with the full Goodwin system - max header + Helmholtz mid pipe + Super Q muffler - I found that combination of parts to produce a very nice sound level and power bump.
If you are 100% sure you only want some added sound and will not want to add a header and mid pipe later - in other words, you are sure you only want a muffler - then you first have to decide how much additional sound you want. I spent a lot of time listening to YouTube clips and asking for feedback on miata.net. Based on all of that info I believe the Cobalt will be somewhat louder than the Super Q, probably 20-25% louder than stock for the Cobalt vs 10% - 15% louder than stock for the Q. If you prefer the louder muffler, you should also consider the Goodwin Roadster Sport II, which seems to be similar in overall loudness to the Cobalt, or the Goodwin Street Single, which is probably a bit louder than both.
The Goodwin Roadster Sport II received high praise on Miata.net from several people who have it and have tried many other mufflers. Based on that positive feedback and the volume increase I'm looking for, I just ordered the Roadster Sport II and haven't received it yet. But I'll be sure to post here and let you know how I like it after I get it on the car.