Yes I know what your on about. You will probably find the way the ECU opens the valve will be programmed so the noise output is within type approval specifically where the test is done. They are also quiet round town which is where a noisy exhaust generally upsets people. My bike has this (EXUP valve) and it does make a huge difference.v8man wrote:thing is some of the new sports cars Aston , Ferrari i noticed they are very very loud when they step on it like after 3k revs i believe they got a valve in the exhaust that opens at pressure and for sure they make like 120 db the way they sound
Fixed link from Ian's post
http://fp.topcateng.plus.com/Garage/SVA ... _draft.pdf
