Wrap Up And Dyno Run - From 88Ci to 106ci With S&S Cycle - Tech

4. The pipe of choice for this hop-up was the ThunderHeader 2-into-1 long pipe in a matte-black finish with matching heat shields. Since we are installing a closed loop system we needed to weld a set of O2 sensor bungs on to the pipes. Eric drilled the holes into the header pipe around the same area as a stock H-D application. Then he welded a set of bungs into the header pipe. Once the pipes cooled down he cleaned the threads with a tap.

5. The S&S Closed Loop Sensor Kit includes two oxygen sensors and hardware, one for each exhaust pipe, to tune the cylinders independently. Here are the plugs for the O2 sensor wires, which were routed back up to the VFI harness, and tucked up under the frame at the seat area.

6. The head pipe was loosely installed onto the engine then the 02 sensors were installed by placing a dab of anti-seize on the threads then tightened down for a good seal.

7. Next, the muffler was installed by placing the hanger bracket through the mount then Eric bolted the two together and the head bolts were tightened.

8. Once everything was all tightened Eric installed the black-coated heatshields onto the header pipe.

9. Here is the black 2-into-1 Thunderheader on the bike. This pipe is really nice looking and adds to the appearance of the bike.

10. The next thing Eric did was install the S&S high flow performance air filter and tear drop cover.

11. Eric connected the PC pin plug from the S&S VFI module to the laptop on the dyno and selected in a base program based on the bike's set-up like the pistons, the cam and the exhaust. This is the starting point for the VFI modules closed loop system to fine tune its program and settings as the bike is ridden. Then the bike was turned back over to the owner (Uncle Vic), who needed to get as many miles on the bike as he could before we put it on the dyno. Over the next three weeks he racked up just over 1,500 miles with trips up to the high desert out to the beaches and up about 4,000 feet of altitude in the SoCal mountains. Vic told us the bike ran great and could not see how it could get better.

12. This is a look at the 3-D graph for the ProTune II software for the S&S 106ci Hot Set up. What you are looking at is a way to see where the bike is making changes at different speeds-to-RPM-throttle opening and timing. From here Eric can see where fuel was added or removed to keep the engine running smoothly with no stumbles or hiccups.

13. The bike was run about 60 more miles then back to the shop for one more run on the dyno.

14. We were not let down with the numbers. Having ridden bikes all his life, Uncle Vic said that "this bike is well over 110-hp, I can feel it." He was not that far off. The bike pulled 108.4-hp and 108.9 ft-lb of torque. We pulled up the ProTune II 3D graph and what we found was the map and the dyno chart were almost a match to the base file. So the bike is doing exactly what it was programmed to do, run at the most efficient way with the most horsepower it can. Before we started this hop-up the bike was pushing 72 hp and 82 lb-ft of torque. So we gained over 36 hp and almost 27 lb-ft of torque. So now Vic is really happy, he brought his old tired bike back to life with tons of horsepower and torque, and now his bike is running with up to date technology with the closed loop system. The addition of the VFI module will allow him to make further modifications and still keep the bike running at optimal performance. As the bike left the shop there was a chirp of the rear tire and a lift of the frontend as he hit the street, and all Vic said was "I'm going to need a new rear tire."