koth442 Posted January 18, 2018 Share Posted January 18, 2018 https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwiexaz94OHYAhUBQKwKHfYZCFwQtwIIKTAA&url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DazPKIjxmmdU&usg=AOvVaw1KGfCjB7R-pOLQBAPBRHk9I'll embed that for you. azPKIjxmmdU '15 FJ09 Link to comment Share on other sites More sharing options...
Premium Member joeszup Posted January 18, 2018 Author Premium Member Share Posted January 18, 2018 Heh, that video is entertaining. I now have MOAR POWAH! Link to comment Share on other sites More sharing options...
Supporting Member betoney Posted January 18, 2018 Supporting Member Share Posted January 18, 2018 Very interesting results in that video. I would have expected complete opposite results. ***2015 Candy Red FJ-09*** Link to comment Share on other sites More sharing options...
Premium Member micah2074 Posted January 18, 2018 Premium Member Share Posted January 18, 2018 It certainly goes against everything I was ever told..... Let’s go Brandon Link to comment Share on other sites More sharing options...
koth442 Posted January 18, 2018 Share Posted January 18, 2018 Back pressure is magic. Trust me, I'm an engineer. '15 FJ09 Link to comment Share on other sites More sharing options...
Supporting Member piotrek Posted January 18, 2018 Supporting Member Share Posted January 18, 2018 Back pressure is magic. Trust me, I'm an engineer.Engineering and magic don't reconcile well in my head . Wouldn't the rest of the missing exhaust system provide the restriction that would yield similar dyno results? Like I said... incomplete system. Link to comment Share on other sites More sharing options...
koth442 Posted January 18, 2018 Share Posted January 18, 2018 Engineering and magic don't reconcile well in my head . Wouldn't the rest of the missing exhaust system provide the restriction that would yield similar dyno results? Like I said... incomplete system. You are right in this case. The system is too open and needs some kind of 'back pressure'. I consider anything that cannot be solved analytically (conventionally) to be magic. The math regarding back pressure CANNOT be solved in the conventional sense. Computer simulations, (Computational Fluid Dynamics, CFD) are run to best approximate what the system *should* do. But at the end of the day, high temperature thermofluid problems are chaotic and have to be empirically tested. No amount of computers or math will suffice. This youtube provides a nice explanation. It may also give you a headache. jjPeP_Nn2B4 '15 FJ09 Link to comment Share on other sites More sharing options...
norcal616 Posted January 18, 2018 Share Posted January 18, 2018 Adding a little backpressure on a 2 stroke sled or bike by tacking a washer to the exhaust can port is magical... 2012 wr250f - C-class 30+ age group 2015 fz-07- Hordpower Edition-80whp 2015 fj-09- Graves Exhaust w/Woolich tune by 2WDW @120whp Link to comment Share on other sites More sharing options...
bigorangecntry07 Posted January 18, 2018 Share Posted January 18, 2018 I am sure @joeszup had already taken a hammer to the other two pipes. HA! Link to comment Share on other sites More sharing options...
Premium Member joeszup Posted January 18, 2018 Author Premium Member Share Posted January 18, 2018 You are right in this case. The system is too open and needs some kind of 'back pressure'. I consider anything that cannot be solved analytically (conventionally) to be magic. The math regarding back pressure CANNOT be solved in the conventional sense. Computer simulations, (Computational Fluid Dynamics, CFD) are run to best approximate what the system *should* do. But at the end of the day, high temperature thermofluid problems are chaotic and have to be empirically tested. No amount of computers or math will suffice.... . Great video... I'd seen this before and actually enjoyed it. I recall driving behind a BMW car a couple of years ago, and noticed that the exhaust system had a butterfly valve on one of the muffler exit pipes. It would close when stopped and open when the car was at speed. That was apparently to 'regulate' exhaust velocity. We digress of course... I am sure @joeszup had already taken a hammer to the other two pipes. LOL... Actually, I bought those pipes up for sale from empire00. When I get them, they are going to be sanded and repainted black (with Rustoleum High Heat Automotive paints). I also ordered a Higdonion "Trail cage and skidplate" in flat black. Probably won't get around to setting up my paint tent until spring, but I'll post pictures when it's put together. For now, I'll just ride with the unintended increased performance Link to comment Share on other sites More sharing options...
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