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I unbolted my muffler yesterday just for fun and i seemed to notice a chuck of my low end power but it feels like i gained some high end. When going to the track is it better to leave the muffler bolted or unbolted???
 

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You'd be better off stripping your CAT and putting a glass pack on for a muffler.. I'm no expert but I'd think lack of back pressure would mess up your rings.
 

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On the track a complete straight through exhaust would get you better times. The muffler isn't there to add backpressure or add power, it's there to muffle sound. The cat also is not there to add power or backpressure, it's job is to clean the exhaust fumes. The key is exhaust pipe diameters, and header primary pipe diameters and lengths. What you want to do is keep your exhaust gas velocity up. At low rpm's a smaller pipe size creates the best flow, at high rpm's larger diameter piping flows better. What we have to do on street cars is find the happy medium between high end power and low end power. It's hard to do this without lots of dyno time. Also to consider is changes in pipe sizes and the bends it takes. These cause wave echos and anti-wave echos to travel back up the exhaust to the manifold. Depending when they hit the opening these echos can either push exhaust gas back into the port (reversion), or help suck it out quicker (scavenging). Obviously, reversion is not good. But again, without dyno time you can't really know what's going on in there. You can start to burn rings in some cases, but usually have to pretty much run open header to do that. If you run no muffler, I would suggest keeping your exhaust size no more than a 1/4" larger than stock to be safe. But really, it depends what other mods you have done. A high power, high flowing engine needs more naturally.
 
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