diamond jim
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For me, I'm all about torque.
There are not many LS650 dyno slips on the net. About half are from the portable dynos that only show hp. So I keep a look out for those that show the torque curve and look especially to see which mods effect how early, how flat, where and how wide in the powerband the torque curve remains above about 28 ft lbs.
From the limited dyno slips posted, it seams that adding a supertrapp and rejetting is the quickest way to gain an easy 10% on the torque side. A supertrapp has the advantage of a short pipe and long pipe. The section where the cone begins to widen fools the bike into thinking it has a shorter pipe thus more torque in the midrange and higher parts of the powerband. However, the cone and discs also imitate the dynamics of a longer pipe and this also helps provide torque in the same manner as a concentric longer pipe. The discs allow one to emulate the restrictiveness of a longer concentric pipe. Viola, best of both worlds. The benefit of a supertrapp on the LS650 cannot be argued. However, the price sometimes sometimes can.
I managed a 15-20% torque increase, albeit after tons of testing and messing around. Consider it the poor man's method. But to me it's all about flow. Intake and exhaust length with appropriate cross-sectional dimensions effect max torque as well as where in the powerband the torque is most prominent. Longer intake and exhaust paths, up tp a point, equal more torque and torque that is shifted more into the lower to midrange portion of the rpm band. Shorter intake and exhaust lengths shift the torque more into the midrange and higher rpms.
A cone filter directly mounted to the carb mouth combined with a shorter pipe (one that ends say 4-5 inches before the rear axle bolt, will have torque shifted more into the mideange to upper rpm. This is the best setup for WOT but at the expense of low to midrange torque. If most of your riding is highway and interstate miles, then this is a pretty good setup for you.
However, I ride in neighborhoods, downtown and stoplight traffic. I do a lot more stop and go and riding under 60 mph. So I want my torque focused in the low to midrange instead so I can get that grin when I turn the throttle. On the LS650, a longer intake track and longer exhaust, both geared towards increasing air velocity, provide that lovely oomph with the tstyle of riding that I do (or did!)
When I first started modding I did the standard cone filter directly on the carb and a sportster muffler. I really thought I was getting all of the grin inducing torque that this little thumper is capable of providing. I certainly didn't realize what I was missing til after the mods.
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