Roar Rules...


no mention of 3 chamber... no one in the US runs EFRA or IFMAR...


just an FYI

10.5 MUFFLER RULES
10.5.1 All vehicles raced at a ROAR-sanctioned event must be equipped with muffler that complies with the following specifications.

10.5.2 The muffler/pipe must be of a multiple chamber design with an internal or external silencer. The maximum inside dimension of the exhaust outlet pipe is .5 inches (13mm). On STC and Sports/GT vehicles, the muffler stinger may not extend more than .4 inches (10mm) outside of body. On Formula vehicles, the muffler stinger must exit within the body shell side pods and point down towards the track surface.


10.5.3 Maximum noise level allowed is 85 dB(A) measured at a 90 degree angle to the direction of travel of the vehicle at a distance of 33 feet, 3 feet above the ground, with the engine at maximum throttle and at all speeds. The Race Director may decide on a different method of noise measurement as long as the results are the same. If there is no noise level equipment available, the Race Director can decide whether a vehicle that produces a noise level in excess of other cars will be allowed to compete.