Interactive exhaust valve

[Red Mist_imp]

My CBR has the same thing. If you remove the servo, the bike yells at you (i.e. it goes into limp-home mode). The one on the CBR is there simply for noise abatement at low RPM's, not for torque curve tuning; there isn't any real difference in power with or without the servo/value on the CBR.

Take a look at the actual test procedure and regulations; low RPM noise is not at issue here. Bikes over 676cc are tested at 55% of maximum RPM, at heavy throttle (aggressive acceleration just shy of wheel-slip or front-end lift). So your CBR1000 is going to be tested at 7150 RPM, with a maximum allowable dB rating of 80 dB. The IEV is not going to be involved with sound abatement, it's there to provide a very flat powerband. The Federal Government has just the one testing procedure for noise, [url=http://www.ecfr.gov/cgi-bin/text-idx?SID=05817b167977b31f19ba4aab4aa93b2b&node=40:26.0.1.2.11.5.17.26.13&rgn=div9]here, and one standard for sound restriction, [url=http://www.ecfr.gov/cgi-bin/text-idx?SID=05817b167977b31f19ba4aab4aa93b2b&node=40:26.0.1.2.11.5.17.3&rgn=div8]here, both offered for our perusal after installing that Staintune.

Another quick point is airbox noise is equally important here. My GSX-R 750, for example, has a very raucous airbox in stock condition; it's known for that feature and most magazine testers mention it. The exhaust note is whisper-quiet but the wide-open airbox lets it breathe very well so it makes very good power while keeping things civil at around 8K. It does have the IEV as was mentioned in another post.