The TRUTH about aftermarket exhaust drone

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In the interests of being fully honest in looking at FI's site I have to admit they do NOT claim "no drone" (reviews here almost universally do though). What their site says is "no rasp" which is true; their comments on drone state that the larger resonators have less, which could well be true but the 18 is the one I'm familiar with so can't say. But that type of inline expanded section isn't apparently how you effectively get rid of drone if the Helmholtz info is to be believed (and it should be since there are lots of examples of people resolving drone with them). The Helmholtz method requires the resonator to be 90 degrees off the exhaust flow, not inline with it.