Originally Posted by Olduwan
Check out the comparison vid I posted in the previous page. It shows the stock mufflers give a "putt putt putt" sound while the nameless do not. Maybe that has something to do with the droning sound below 2k with the stock mufflers?
Well there is certainly an element of 'shake the house' on the factory mufflers that does not exist on our straight pipe design. Even our customer the day after he took them home noted that the plates didn't shake on the shelves when he fired the car up anymore. It's most likely something that has to do with the factory baffling design. See, the factory mufflers have chambers in them that act to store exhaust waves and bounce them back toward the source in order to cancel noise. Unfortunately these systems are static so you get different effects at different points in the powerband and with different exhaust flow rates.
That's the best I can do to explain why a factory baffled muffler has more resonance than a muffler delete that has about ~5dB higher amplitude at the same rpm.