Let y'all know what they say.Ĭlick to expand.It's been a while since I last did this and I already forgot all the details. so I've emailed them and asked about increasing intake area and/or shortening pipes. So it seems the airbox is a restriction - 94.20 CFM from a filter that can do 167.70 CFM.

Did I get that right? I'm sure DNA did so maybe I'm a little off, and/or they calcuated for a lower max rpm. That's 166.5 cubic feet per minute - about the same as the OEM filter (not airbox?) and a little more than DNA's stage 2 filter. A four stroke triple at 10,600 rpm is drawing in 265 of each cylinder volume per second, and 15,900 per minute. How much flow does the engine need? Each cylinder is going to draw in 296.67 cubic centimetres at each induction, which is 0.0104766842253 cubic feet. But, P-Y9N21-01 – the drop in replacement - page says OEM Air Filter Air Flow: 167.70 CFM and DNA Air Filter Air Flow: 210.80 CFM. The P-Y9N21-S2 page says Stock Airbox and OEM Air Filter Air Flow: 94.20 CFM and DNA Air Filter Air Flow: 145.80 CFM. The Stage 2 air filter replaces the top and inlet pipes. I also checked out DNA's website cos they do two air filters for this bike. The nearest equivalent speaker enclosure design is a bass reflex but 3 ports in that would sum to 1 not work as 3 different ones as I think they do in an airbox - this video gives an explanation - skip to about 5mins in to see visuals of resonance. 10,600rpm is 265Hz, so the box is experiencing a frequency range similar to a woofer, with three resonant frequencies. The firing order is, I think, every 240 degrees, so induction will be the same, and that's a regularly spaced pulse for a normal sounding 30Hz. For a 4-stroke there's an induction every second revolution so that's 10 inductions per second, and for a triple, that's 30 per second. The lowest idle speed is 1200rpm, so divide by 60 for seconds (so we can get Hz) and that's 20 revolutions of the crank per second. I did some maths on the frequencies - maybe someone can check it for me as my brain is rather old. or even share their experience of changing the airbox. I am trying to understand this very cool airbox - hoping someone will step in and correct me.

Yamaha mt09 ecu flash