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Discussion Starter · #1 · (Edited)
I recently added 3.5" Rinehart Racing slip-ons on a Scout Bobber and immediately noticed/felt a significant (like 30-40%) loss in torque across the usable rev range. Is this expected? Does anyone have a dyno chart for Scouts with a free flowing exhaust. Especially interested in numbers between 2000-4000 rpms.

Any tips or pointers on ECU tuning/reprogramming or perhaps use of torque inserts, baffles etc.

Thanks in advance!
 

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Yes, there are many stage 1 dyno charts in here. I suggest you carefully examine stock and stage 1 Trq production..

If 2k-4k rpm are your primary concern, you'll need stock slipons or tiny "same as stock" baffles in your slipons. If you want stock Trq production, you must provide "stock like" gas velocity through the slipons.

If you want bigger power everywhere, add a S&S air cleaner and a PV3 from Fuel Moto. Flash the FM stage 1 tune and hang on !
 

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Old post but anyway. The loss of low/mid torque is because the full open slip ons create issues with “ reversion” which some people think is just “back pressure“. Read up on this . A lot of Scout buyers are willing to trade off some loss at the bottom to make big gains at top. Fine if you Like riding the higher RPMs A lot. As Indianster posted, you will need to get some restriction back in your mufflers. This is accomplished with baffles or cones in the muffler. One company sells a round wavy disc with a stud that will have you install about 1-1/2” from the exit end of the muffler. Also see “ Exhaust “Loly pop” . I too wanted my lower and mid range RPM torque back after installing performance intake, Khrome Werks mufflers and a FM tune. Replacing the performance baffle ( “straight through) for their “touring baffles” did the trick. ( Not the Dog ball type). Read up on how many people w/Harley Sportsters put on straight pipes only to hate the drivability Problem they just created. . A trick for them was to install a big flat washer with a threaded stud Welded to it and installed midway in the pipe. ( look up “ Snuff or not”, “Loly pop” for exhaust). Also Read up on exhaust reversion . With all that said ,the Scout motor is a short stroke motor ( opposite most all HD Long stroke Motors). The Scout Engine loves to rev Because of the larger bore/shorter stroke . Opening these motors up via more open exhaust, HP intake ,and a Tuner will make big gains at higher RPM at the sacrifice of lower . One reason that a lot of people like Harley bikes is- The Torque range is very usable for the street, a very satisfying pull from low/mid RPMs. Racing and or higher RPM not so much.
 
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