Horsepower Inc.

Horsepower Inc. (HPI) Exhaust & Performance Parts for Harley-Davidson

Horsepower Inc. (HPI) manufactures American-made performance parts for Harley-Davidson motorcycles, specializing in stainless steel exhaust systems, high-flow throttle bodies, air cleaners, fuel injectors, and intake components. Founded in 2002, HPI has become a respected name in the V-Twin performance industry, with in-house manufacturing, exhaust fabrication, engine building, and dyno tuning operations in Indianapolis, Indiana.

At Get Lowered Cycles, we carry HPI exhaust systems and performance components for Milwaukee-Eight Touring, Softail, Dyna, FXR, and select Twin Cam applications. Whether you're upgrading a stock Road Glide, building a high-compression Low Rider S, or assembling a large-displacement performance engine, Horsepower Inc. offers components designed to support your build.

HPI Exhaust Systems for Harley-Davidson

Horsepower Inc. stainless steel 2-into-1 exhaust systems are among the brand's most recognizable products. Handmade in the USA and TIG welded at HPI's facility, these exhaust systems combine craftsmanship with performance-oriented header and muffler designs.

HPI offers different exhaust lengths and configurations for compatible Harley-Davidson motorcycles. The right system depends on your motorcycle, engine combination, preferred exhaust appearance, and intended riding characteristics.

Explore the available Shorty, Mid-Length, and Full-Length exhaust systems below to find the configuration that works best for your Harley.

HPI Shorty 2-Into-1 Exhaust

The HPI Shorty is a popular option for performance Harley builds where a compact exhaust appearance is preferred. Its shorter muffler layout creates a distinctive profile while retaining HPI's stainless steel construction and hand-welded craftsmanship.

Shorty exhaust systems are available for select Milwaukee-Eight Touring, Softail, and earlier Harley-Davidson applications.

The exhaust's compact design is particularly appealing on performance baggers and custom builds, although clearance, mounting requirements, and engine characteristics should all be considered before choosing a shorter system.

Explore the HPI Shorty Stainless 2-Into-1 Exhaust for 2017-2025 Harley Touring.

HPI Mid-Length Exhaust for Harley Touring

The HPI Mid-Length 2-into-1 exhaust offers a configuration between the compact Shorty and longer Full-Length systems. Designed for compatible Milwaukee-Eight Touring motorcycles, this exhaust combines a mid-length muffler layout with HPI's handmade stainless steel construction.

The system features TIG-welded fabrication and a perforated stainless steel muffler interior. Its sound and operating characteristics depend on the motorcycle's engine displacement, camshaft, exhaust calibration, and other modifications.

One important installation consideration is the mounting arrangement. HPI's Mid-Length Bagger exhaust requires compatible lower saddlebag support rails and is not compatible with certain aftermarket crash-bar or subframe arrangements.

View the HPI Mid-Length Stainless 2-Into-1 Exhaust for 2017-2026 Harley Touring.

HPI Full-Length Stainless 2-Into-1 Exhaust

For riders who prefer a longer exhaust profile, Horsepower Inc. manufactures Full-Length stainless steel 2-into-1 exhaust systems for compatible Harley-Davidson Touring motorcycles.

These systems combine HPI's handcrafted stainless steel construction with a full-length exhaust layout. They are a popular consideration for Street Glide, Road Glide, and Road King riders building performance-oriented touring motorcycles.

Choosing a Full-Length exhaust should involve more than appearance alone. Muffler design, collector dimensions, engine displacement, camshaft selection, and professional tuning all influence the finished combination.

Browse the HPI Full-Length Stainless 2-Into-1 Exhaust for 2017-2026 Harley Touring.

HPI Shorty vs. Mid-Length vs. Full-Length Exhaust

Horsepower Inc. offers several exhaust configurations to accommodate different performance builds and styling preferences.

• Shorty: A compact exhaust configuration suited to riders who prefer a shorter, aggressive appearance.
• Mid-Length: A balanced visual profile between shorter and longer exhaust designs, with application-specific mounting and saddlebag clearance requirements.
• Full-Length: A longer exhaust configuration popular with performance Touring builds and riders who prefer a traditional full-length layout.

No single exhaust length is automatically best for every engine. Actual horsepower, torque, and throttle-response characteristics depend on the complete engine combination and calibration.

For a stock or mildly modified Milwaukee-Eight, selecting the proper exhaust should account for sound preference, riding style, and fitment. For larger-displacement engines or aggressive camshaft combinations, exhaust selection should also be evaluated alongside dyno results and the intended RPM operating range.

HPI Exhaust for Milwaukee-Eight Softail

Horsepower Inc. also manufactures stainless steel exhaust systems for compatible Milwaukee-Eight Softail motorcycles, including select Low Rider S, Low Rider ST, Street Bob, Fat Bob, and other Softail applications.

HPI Softail exhaust systems offer handmade construction and performance-oriented styling for custom Harley builds.

When selecting an exhaust for a Softail, pay particular attention to model year, engine generation, foot controls, passenger peg clearance, saddlebags, and any aftermarket mounting components.

Explore the Horsepower Inc. Stainless Exhaust for 2018-2025 Harley Softail.

HPI Exhaust for Dyna & FXR

Horsepower Inc. offers stainless steel exhaust systems for select Harley-Davidson Dyna and FXR motorcycles. These exhausts are appealing to riders building performance-oriented Twin Cam and Evolution-powered motorcycles.

Dyna and FXR platforms have different mounting requirements, engine configurations, and chassis clearances. Selecting the correct exhaust requires verifying the motorcycle's year, transmission arrangement where applicable, and compatible mounting components.

Browse the HPI Stainless Exhaust for Harley Dyna or the available FXR exhaust systems in our Horsepower Inc. collection.

HPI Throttle Bodies for Milwaukee-Eight Engines

Horsepower Inc. is also known for its high-flow throttle bodies, designed for riders looking to improve intake airflow on performance Harley-Davidson engines.

HPI offers billet throttle body assemblies for compatible 2017-2023 Milwaukee-Eight motorcycles in multiple bore sizes, including 58mm, 62mm, and 70mm configurations.

These throttle bodies are particularly relevant when planning a larger-displacement M8 build, upgraded cylinder heads, or other airflow-intensive engine modifications.

Choosing the correct throttle body size is important. A larger diameter does not automatically produce better performance throughout the RPM range. Intake velocity, engine displacement, cylinder head flow, camshaft characteristics, and calibration all influence the result.

Explore the HPI Throttle Bodies for 2017-2023 Harley Milwaukee-Eight.

Horsepower Inc. V2 Air Cleaners

HPI V2 air cleaners are designed to improve intake airflow while providing a compact, performance-oriented appearance.

The V2 design incorporates a velocity-stack-style intake configuration intended to promote airflow into the throttle body. Different covers and application-specific backplates are available depending on the motorcycle and engine generation.

For first-generation Milwaukee-Eight applications, browse the Horsepower Inc. V2 Air Cleaner for 2017-2023 Harley M8.

HPI also offers Center-Cooled V2 Air Cleaners for compatible newer-generation Milwaukee-Eight engines, including select 2024-up Touring and 2025-up Softail applications.

Explore the HPI Center-Cooled V2 Air Cleaner for Newer M8 Models.

These air cleaner systems are not universally interchangeable. Confirm the correct Milwaukee-Eight generation, throttle body size, engine configuration, and product fitment before ordering.

HPI Intake Manifolds & Tunnel Ram Components

For riders building higher-output Milwaukee-Eight engines, Horsepower Inc. offers performance intake manifolds and Tunnel Ram components.

HPI's CNC-ported intake manifold is designed for compatible first-generation Milwaukee-Eight applications and offers an upgraded intake pathway compared with the original plastic manifold.

The company also manufactures Tunnel Ram intake components intended for specific throttle body configurations and engine combinations.

Browse the HPI CNC-Ported Intake Manifold for 2017-2023 Harley M8 or the Horsepower Inc. Tunnel Ram Elbow.

Manifold and intake compatibility should be checked carefully, especially when using aftermarket cylinder heads, larger throttle bodies, custom fuel rails, or external breather systems.

HPI Fuel Injectors for Harley-Davidson

Horsepower Inc. manufactures fuel injectors for compatible fuel-injected Harley-Davidson engines, including Milwaukee-Eight applications.

When upgrading a Harley engine with increased displacement, higher compression, performance cylinder heads, or an aggressive camshaft, the fuel system must be capable of supplying the required fuel throughout the operating range.

Injector selection should be based on the engine's actual fuel requirements, available fuel pressure, injector flow characteristics, and calibration strategy.

Simply installing larger injectors does not automatically increase horsepower. The engine management system must be properly calibrated to account for the selected injectors.

Explore the HPI Fuel Injectors for 2017-2023 Harley M8.

Choosing HPI Parts for a Performance Harley Build

Building a reliable performance Harley-Davidson requires selecting components that work together rather than choosing individual parts solely by their advertised dimensions.

Consider the following before selecting an HPI exhaust, throttle body, air cleaner, or fuel-system component:

• Engine displacement: A stock Milwaukee-Eight and a larger high-compression engine may have significantly different airflow and fuel requirements.
• Camshaft characteristics: Cam timing and intended RPM range influence how an engine responds to intake and exhaust changes.
• Cylinder head airflow: Intake port dimensions and cylinder head flow should be considered when choosing larger throttle bodies and manifolds.
• Fuel system capacity: Injectors and related components must support the engine's required fuel delivery.
• Motorcycle fitment: Exhaust mounting, frame clearance, saddlebag supports, and engine-generation differences matter.
• Professional tuning: Appropriate calibration helps the components work together and supports consistent engine operation.

A well-matched intake, exhaust, fuel system, and calibration can deliver a more usable performance combination than simply installing the largest available components.

Frequently Asked Questions About Horsepower Inc.

Are HPI exhaust systems made in the USA?

Yes. Horsepower Inc. manufactures its stainless steel exhaust systems in the United States. The company performs fabrication and TIG welding in-house at its Indianapolis facility.

Which HPI exhaust is best for a performance bagger?

That depends on the motorcycle and engine setup. HPI offers Shorty, Mid-Length, and Full-Length configurations. Compare fitment, installation requirements, preferred sound, appearance, and dyno-tested performance for your engine combination.

Does a bigger HPI throttle body increase horsepower?

A larger throttle body can support additional airflow when the engine requires it, but bigger is not always better. Engine displacement, cylinder head flow, camshaft selection, intake design, and tuning determine whether a particular throttle body size is appropriate.

What's the difference between HPI V2 and Center-Cooled V2 air cleaners?

They are designed for different Milwaukee-Eight intake applications. The standard V2 lineup includes first-generation M8 fitments, while Center-Cooled V2 versions accommodate compatible newer Gen II Milwaukee-Eight configurations. Verify the specific engine and throttle body application.

Do I need tuning after installing HPI performance parts?

Tuning needs depend on the motorcycle and modifications. Larger throttle bodies, different injector flow rates, and significant intake or exhaust changes may require revised calibration. Consult an experienced Harley-Davidson tuner.

Can HPI performance parts be used on a stock Harley engine?

Some HPI products are suitable for stock or mildly modified engines, while others are intended for more extensive performance builds. Always choose parts based on the motorcycle's existing configuration and intended use.

How long does an HPI exhaust take to ship?

HPI exhaust systems are handcrafted, and manufacturing lead times can vary. Check the individual product's availability and current fulfillment estimate before ordering.

Are HPI exhaust systems emissions compliant?

Emissions requirements vary by application and jurisdiction. Certain HPI performance exhaust systems are intended for racing applications and may not be legal for use on emissions-controlled motorcycles on public roads. Review each product's emissions notice before purchasing.

Shop Horsepower Inc. Parts at Get Lowered Cycles

Get Lowered Cycles carries Horsepower Inc. exhaust systems, throttle bodies, air cleaners, fuel injectors, manifolds, and other performance components for Harley-Davidson motorcycles.

Whether you're building a Milwaukee-Eight Softail, upgrading a Road Glide or Street Glide, or working on a custom Dyna or FXR, browse our Horsepower Inc. selection above to compare available components and motorcycle fitment.

You can also explore our complete selection of Harley-Davidson Air Cleaners and Harley Touring Exhaust Systems to compare additional performance options.

Get Lowered Cycles offers free U.S. shipping with no order minimum. If you're unsure which Horsepower Inc. parts are right for your motorcycle, our team can assist with compatibility and product selection.