There’s no big secret to making power in the V-Twin engine; just cram as much air as you can into the cylinders on the intake stroke, add the correct proportion of fuel, then efficiently burn the air/fuel mixture on the power stroke. However, the way you go about stuffing the cylinders is a matter of choice. Some power junkies follow the “no replacement for displacement” route. And that’s cool. But others lean toward power-adders.
LifeStyle Cycles believes in both philosophies for making big power numbers. LifeStyle’s crew is well-versed in the intricacies of hopping up V-Twin motors and has a well-equipped shop to get the job done. As such, Junior, LifeStyle’s owner, thought it was about time to build a new project bike with a supercharger power-adder as the first phase of an evolutionary power-development project. Located in Anaheim, CA, LifeStyle Cycles invited the staff of HOT BIKE magazine to follow along as the crew there installed an Accessible Technologies Inc. (ATI) ProCharger supercharger on a bone-stock Twin-Cam 88 EFI Fat Boy.
Unlike a naturally aspirated engine, which relies on atmospheric pressure to fill the cylinders, a supercharger (aka a blower or power-adder) is a crank-driven compressor that forces huge amounts of air into the engine’s cylinders, increasing engine power dramatically. Currently, there are two designs of superchargers available for the V-Twin engine: roots and centrifugal. Where a roots-style blower uses spinning rotors to develop pressure or boost, a centrifugal blower uses a fan-like impeller rotating at high speed to develop boost. Although a centrifugal blower may look similar to a turbocharger, it’s different. Turbochargers are powered by hot exhaust gases, where superchargers are crankshaft-driven. Since it’s crank-driven, there is no power lag with a supercharger, and boost starts instantly right off idle and builds as rpm increase.
In case you haven’t already heard of ATI, the company is well-known in the automotive industry for offering reliable supercharger applications for increased power. As such, it has applied proven supercharger technology from the automotive world to the V-Twin engine, including intercooling for optimized power. ATI chose a centrifugal-style supercharger for its ProCharger kit because a centrifugal design is compact and can be spun at higher rpm for high boost and efficiency, reducing the temperature rise of the compressed intake charge and parasitic power losses. ATI then took supercharging the V-Twin engine one step further by adding a neat intercooler to its ProCharger package. The intercooler is an air-to-air heat exchanger that reduces the elevated intake charge temperatures exiting the supercharger. These lower temperatures increase air density, which is critical for increasing power at high rpm when the charge air is highly compressed and substantially heated.
ATI’s ProCharger system offers excellent craftsmanship and comes as a complete bolt-on kit, including all required parts and fasteners. Major components include the compact supercharger, stylish intercooler, drive assembly, and ducting. All parts are symmetrically positioned on the motorcycle for clean aesthetics and excellent balance. The crew at LifeStyle Cycles took less than five hours for the complete installation on the EFI-equipped Fat Boy, not including the time on the dyno. ATI offers both carbureted and EFI ProCharger kits and includes a Power Commander unit for precise fuel and ignition tuning on EFI-model bikes. An added benefit of the ProCharger is that it can be easily removed and installed on a different bike. (Check out the included dyno chart to see how ATI’s ProCharger kit achieved about 106 horsepower [a 74-percent increase over stock] with 10 pounds of boost on a bone-stock TC-88 Twin-Cam engine.)