Has anyone used the Dynomax Ultra Flo X or VT mufflers? Looking to build a system that won't attract attention on the road but not break sound limit (95dB) at the track. Also hoping to pump up the 3.1 at some point so want the exhaust to be ready for 200 (or more?) hp. Also, any merit or otherwise to having the pipes and muffler(s) fixed solidly and use flexible couplings to the headers?

 

Not those ones specifically but i have done alot of work with dynomax ultraflo round mufflers on 3 cars and various motor setups. Also x pipe y pipe experiments. Those dynomax ultraflos really quiet a car down. Thicker case is quieter than thinner like dynomax bullets.
An X pipe added to a dual system does change the sound for the better. Eliminates some lower frequency noises and muffles some of the exhaust noise by itself.

Combining it into 1 muffler, x and ultra flo porting, it would be nice and quiet yet no real restriction, especially for a 3.1

 

Thanks for the input. I'm considering the Ultra flo and having two output pipes and using one inlet and blocking off the other until I get rid of the Y and then use the other inlet.

 

How quiet do you want? I found that I couldn't show a difference on back to back runs with and without a muffler (put a flange in front of the muffler so I could take the muffler and tailpipes off in less than a minute) at the track with a stock 4th gen exhaust with a stockish lt1 and a lot of spray running 11s... find someone that took their stock exhaust off a 4th gen and get that for next to nothing- quiet and fast. Otherwise put a 2.75 or 3" intermediate pipe on it adn whatever muffler you like the sound of on it... it will be fine for 200hp