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post #11 of 14 (permalink) Old 12-05-2012, 01:05 AM
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All the aftermarket pipe makers I have seen build pipes with an eye for HP, but free flowing pipes breathe easier and rev faster so you get to the torque quicker. the firing order controls where the torque is too, the 270 deg. in the scram/speedmaster/america is going to be more torquey than the 360 deg in the bonny/thrux. Cams will keep the party going building torque all the way to redline.
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post #12 of 14 (permalink) Old 12-05-2012, 02:22 AM
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You can increase torque right through the rev range by fitting free flowing pipes and making the airbox flow easier, but after these mods any additional low down torque can only be gained by big bore or higher compression pistons.

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post #13 of 14 (permalink) Old 12-05-2012, 07:48 AM
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Originally Posted by ClimberClint View Post
Can you post an example or two of pipes tuned to capitalize on the low end differences in the camshafts versus making HP? Are there general types of exhaust systems that provide more of one or the other (i.e. 2 - 2 vs 2 - 1) or are they specific to the pipes models/makes themselves?

I'm not familiar with all the pipes out there, but most are set up to open things up and allow the bike to flow at higher RPMs. In general, exhausts that make the most low end are ones with smaller primary pipe diameters and longer primary pipe lengths...these maximize scavanging at lower rpms.

On the intake side, you can also tune to maximize torque by increasing the intake tract length.


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post #14 of 14 (permalink) Old 12-05-2012, 10:47 AM
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You can get some small gains in low in torque with the normal mods but they are small gains at best a few ft/lbs not enough to make these bikes a stump puller,these are not low end motors like a HD.The only way to see much of a gain is to go up in cc with a big bore /stroker motor.Any change in gearing is just a trade off low speed /high speed.
A look at the dyno post and its easy to see .People get good hp out of the 865 motors with hc pistons,cams ,head work ,pipes and so on.But a 904 will allways make more torque then a 865 with the same mods.The bigger cc you go the bigger the torque gets.
The stroker motors allso make more torque then the same size bore stock stroke motors.

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