Exhaust Valve Controller

As can been seen from the graph, the optimum point to close the p/valves (on this bike), would be approx. 7100rpm,where approx. 8bhp would be realised from 7100 to 8300 rpm. This very much depends on how mismatched the p/valves are to start with. The example shown had been optimised for mid range power, with loosing too much top end, before adjusting the p/valves. However, although Suzuki say the valves turn at 7800 this varies by at least +/-200rpm. There is a time delay from p/valves starting to close to actual closing point, we have tried to address this by adding a circuit to sense rate of change of rpm . A high rate of change will start to open the valves approx. 180 rpm earlier,(1st or 2nd gear) and a low rate of change (6th gear) will start to open the p/v's 180 rpm later than set. In the example p/v's started to turn at approx. 8200rpm. The best way to find the optimum point is by running on a dyno with valves fixed closed, and then open, to get the curves as above. The range of adjustment is from 6000to 8000 rpm with a calibrated and graduated scale. There is also a calibration pot (which should not require adjustment) that could be used to extend the range.

Contact
www.bdkraceeng.co.uk