MAIL baggersmag@sorc.com 01. This is HPI’s drop-in replacement 51mm big-bore throttle body for ’06-present cable-operated Harley-Davidsons (MSRP $695). The unit came with everything Matt needed to swap out his stock setup, including the throttle body and new flanges and gaskets. Matt also got some of HPI’s 5.3gps high-flow injectors (MSRP $180). HPI also offers Fly-by-Wire throttle body assemblies for late-model baggers.01. This is HPI’s drop-in replacement 51mm big-bore throttle body for ’06-present cable-o Efficiency and power are two of the aspects that attract people to the modifications of an engine. The great thing about Harleys is that upgrading their performance is a straightforward procedure. That thinking is what’s behind Horsepower Inc.’s (HPI) 51mm throttle body and 5.3gps injector kit: it flows more air due to the increased diameter and machined and polished intake runners—it also delivers more fuel with larger injectors. These two factors (when complemented by an increase in displacement) are known as one of the classic combinations to make more power. When considering an engine upgrade, performance isn’t the only deciding factor, many riders that depend on their bikes for daily transportation also require reliability. Such was the case with Matt Cortez, one of the head technicians at Anaheim-Fullerton Harley-Davidson. His daily rider, an ’07 Road Glide, had already been upgraded to 103 ci, and he knew it was starving for air and fuel. With the considerably larger displacement, the stock 46mm ID throttle body was restricting its potential to make power. HPI’s larger throttle body and injectors were the answer. 02. All of HPI’s throttle bodies and manifolds are American-made, precision CNC-machined, hand ported and polished, and flow bench tested. The throttle bodies feature a stainless steel shaft and spring that help resist corrosion and a double roller bearing for smooth operation and response. Horse Power Inc. also uses an increased-strength brass throttle blade and shaft to resist deflection and to help maintain throttle position accuracy and absorb vibration and engine harmonics.02. All of HPI’s throttle bodies and manifolds are American-made, precision CNC-machined, In a few short hours, Matt was able to swap out the restrictive stock throttle body and replace it with HPI’s throttle body. Horse Power Inc. engineered the swap to be easy and affordable by allowing the use of the original equipment sensors, lines, and cables. Adding to the ease of installation is the fact that most of the sensors only fit in their proper receptacles and their corresponding connectors are unique to each sensor as well, allowing very little room for installation errors. B 03. The HPI throttle bodies and manifolds are two-piece units that are roughcast out of 6061 billet aluminum. Horse Power Inc. offers its throttle bodies and manifolds as two separate pieces because they have various throttle body sizes and manifolds with a variety of intake runner diameters. By offering the two-piece units, it allows customers to mix and match throttle bodies and manifolds accordingly for their specific engine setup. After casting, the throttle bodies and manifolds go into one of HPI’s five-axis CNC machines to get ported.03. The HPI throttle bodies and manifolds are two-piece units that are roughcast out of 6 03. The HPI throttle bodies and manifolds are two-piece units that are roughcast out of 6061 billet aluminum. Horse Power Inc. offers its throttle bodies and manifolds as two separate pieces because they have various throttle body sizes and manifolds with a variety of intake runner diameters. By offering the two-piece units, it allows customers to mix and match throttle bodies and manifolds accordingly for their specific engine setup. After casting, the throttle bodies and manifolds go into one of HPI’s five-axis CNC machines to get ported.03. The HPI throttle bodies and manifolds are two-piece units that are roughcast out of 6 05. When it came to installing the HPI throttle body, the process was relatively simple. First Matt removed the gas tank, air-cleaner cover assembly, throttle cables, every connector attached to the stock throttle body, and removed the throttle body assembly from the heads of the motor.05. When it came to installing the HPI throttle body, the process was relatively simple. 06. Next he extracted all the sensors and brackets attached to the exterior of the stock throttle body—the only exception being the spring for the butterfly.06. Next he extracted all the sensors and brackets attached to the exterior of the stock 07. Here we see the big difference (other than the looks) of the stock throttle body compared to the HPI unit. The stock throttle body measures in with a 46mm inner diameter…07. Here we see the big difference (other than the looks) of the stock throttle body comp 08. …while the HPI version is expanded 5 mm over stock for a total inner diameter of 51 mm.08. …while the HPI version is expanded 5 mm over stock for a total inner diameter of 51 m 09. Every sensor is important to the tuning of the fuel system and should be handled with care. If you notice any that are damaged, now’s the time to place them. Matt gently cleaned the O-rings and gasket surfaces, taking care not to damage the delicate sensors. He then plugged them into the HPI unit it in the same orientation as the stock throttle body. Matt then started replacing the sensors, starting with the idle air controller.09. Every sensor is important to the tuning of the fuel system and should be handled with 10. Matt made sure to use thread-locker on the bracket and sensor fastening bolts. A loose sensor can give false readings that can harm gas-mileage and performance.10. Matt made sure to use thread-locker on the bracket and sensor fastening bolts. A loos 11. Next, Matt installed the Manifold Air Temperature sensor… 10. Matt made sure to use thread-locker on the bracket and sensor fastening bolts. A loose sensor can give false readings that can harm gas-mileage and performance.10. Matt made sure to use thread-locker on the bracket and sensor fastening bolts. A loos 12. …followed by the throttle cable bracket. 13. In addition to significantly more air into the motor, HPI also recommends upgrading the injectors. Their 5.3gps injectors squirt 23 percent more fuel than their OEM counterparts, and the spray pattern is engineered to optimize fuel atomization. Matt inserted the injectors into the fuel rail first.13. In addition to significantly more air into the motor, HPI also recommends upgrading t 14. He then attached the fuel injector assembly onto the throttle body. 15. Matt made sure the assembly fit snugly, but was not forced into place, and then he tightened it down.15. Matt made sure the assembly fit snugly, but was not forced into place, and then he ti 16. The kit also comes with a set of new intake manifold flanges and gaskets. Matt had them in place in seconds.16. The kit also comes with a set of new intake manifold flanges and gaskets. Matt had th 17. After the stock sensors, fuel injectors, and brackets were in place, Matt installed the new throttle body unit on the motor…17. After the stock sensors, fuel injectors, and brackets were in place, Matt installed t 18. …and tightened down the assembly. 19. He then fit the throttle cables back into cable bracket 20. Finally, he attached the fuel line to the injector assembly and attached all the connectors to their corresponding sensors.20. Finally, he attached the fuel line to the injector assembly and attached all the conn 21. The successfully installed HPI throttle body looked much better than the stock unit with its polished machined aluminum surfaces peeking out from between the cylinder heads—and it performed better, too!21. The successfully installed HPI throttle body looked much better than the stock unit w 22. The true indication of a performance-oriented part is how and where it increases power. Most hop-up parts make increases in a single area (like the low-end or top-end), but HPI’s throttle body and injectors increased horsepower and torque across the entire power band, with a peak gain of about 5 lb-ft of torque. You may notice the dip in the 2,500-rpm range—that can easily be smoothed out with some fine tuning. But Matt’s overall response was that the bike felt more responsive and the throttle was much snappier, making the bike much more fun to ride.22. The true indication of a performance-oriented part is how and where it increases powe Source Anaheim-Fullerton Harley-Davidson (714 871-6563 | harleyfullerton.com Horsepower Inc. (814) 836-5782 | hoursepowerinc.net By Greg Friend At Gearhead Inc. Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!
