Yeow! That's a whopping
10.4 horsepower increase
and an addtional 6.1 foot-pounds of honest torque.
- Easyriders Magazine
Easyriders August 2002
Issue 350
Pgs. 130-132
Buy Power PACCs for Evolutions
Buy Power PACCs for Twin Cam 88s
Buy Power PACCs for Sportsters
Buy Power PACCs for Indians
Doherty Power PACC, It's The Real Deal
When you're after quick-and-easy to perform alterations that improve the performance on your Harley-Davidson, little compares with hardware designed to enhance the engine's breathing.
Just simple air intake and exhaust upgrades can provide gains in both torque and horsepower. In the vast majority of applications these mods can be handled with minimum of hands-on mechanical ability, specialty tools and time.
For years enthusiasts have recognized and realized the benefits of replacing the stock air filter element with a unit simiar to K&K's. These high-flow filter provide the engine with a higher volume of air at a less restricked rate.
The most popular filter are easilty cleaned for extended use with no loss in performance. Okay, so you've presented the carburetor with a larger mass of air to ingest. Is that it, or would manipulatoin of the swirling mass provide even grater benefit. Hmm. That question was not lost on the ace engineering team at Doherty Machine.
Tim Doherty had long speculated that if the shape and movement of the air mass between the cleaner and carb could be controlled, engine breathing and performance would be enhanced.
Tim Doherty had long speculated that if the shape and movement of the air mass between the cleaner and carb could be controlled, engine breathing and performance would be enhanced.
To that end he developed a sophisticated, easily installed intake package known as the Power PACC, which Tim Doherty claims will produce real-time torque and horsepower gains you can feel.
Initially, Doherty developed this unique system as a means of controlling air between the filter and carb. Focusing on patented "snap-in" venturi extension, the unit provides predicable air management to the entrance of the carburetor. As one might expect, the extension increases air speed velocity while reducing turbulence.
Additionally, Tim found the new venturi configuration acts to collect and straighten out the air once it has cleared the air filter element. This in turn allows for a smooth and uninterrupted transition to the carb entrance. Unlike traditional velocity stacks, which can negatively affect low rpm performance, Power PACC's "short" venturi runner length offers increased torque on the bottom end.
Benefits of the Power PACC system
The Power PACC system offers others significant benefits not to be overlooked.
Machined from a solid piece of 3/4-inch billet aluminum, Doherty's 1-piece backing plate provides a structurally sound, rigid platform for the tentire intake assembly while eliminating all flimsy bracketry. Furthermore, the Power PACC, as tested, incorporates Doherty's revolutionary Power Vent Twin kit.
Power Vent is a fast sealing, one-way valve that prevents air from being sucked back into the crankcase on the piston's upstroke. This venting method can increase horsepower and throttle response while eliminating rocker box and base gasket leaks often cause by excessive crankcase pressure. Power Vent is a convenient addition to the Power PACC kit since the highly polished billet aluminum vents bolt directly to the cylinder head breather outlets using the same stainless banjo bolts that secure the backing plate.
Quick and Simple Installation Process
Before we lay out the results of the Power PACC let's walk you through the installation process so you can see just how quick and simple it really is.
First off, let the engine cool and slip on some decent eye protectoin. This is a good time to familiarize yourself with the operation by reading the instructions.
Remove your stock air cleaner assembly including cover, filter, tin backing plate and breather lines. Clean up any lingering road grunge, taking care that nothing makes its way into the intake channel. This is not a good place to lay screws while doing an installation.
Take one of the nylon washers from the kit and place it over the breather bolt. Run the bolt through one of the Power Vents followed by a second nylon washer. Thread the bolt into the cylinder head breather outlet. Ditto for the other breather. Install the supplied gasket, with the adhesive side toward the carburetor/injector.
Using the three supplied Allen head screws, install the Power PACC backing plate. Align the two slotted holes in the backing plate with the breather botls and secure using the supplied button head screws and washers. Lubricate the O-ring fit to the velocity stack and then press into the backing plate.
Set the air cleaner onto the backing plate and secure using the three screws and touch of Blue Loctite. Reinstall the air clean cover and that's it. Installation takes only 20 to 30 minutes max using tools your ol' lady commonly throws at you. It's that simple.
Power PACC Performance Evaluation
For a completely unbiased evaluatoin of Doherty's Power PACC we fired up a new 2002 FXSTI and headed over to see Troy and Jim in the service department at Grand Canyon Harley-Davidson. Just prior to and right after installation the bike was put through its paces on the dynometer. We think the dyno graph and horsepower/torque readings speak for themselves.
Only 27 minutes separated the before and after runs which is further evidence of how simple the installation is.
Our first dyo run with the bone stock Delphi inject Twin Cam produced a maximum of 63.1 horsepower and 72.8 foot-pounds of torque. The very same engine after installation of the Power PACC kit produced readings of 73.5 horsepower and 78.9 foot-pounds of torque.
Yeow! That's a whopping 10.4 horsepower increase and an addtional 6.1 foot-pounds of honest torque. Those numbers come straight from the dyno's mouth and are about as honest as you're gonna get. It appears that not only are Doherty's performance claims realistic, they may even be understated.
The complete Doherty Power PACC kit contents
The complete Doherty Power PACC kit includes their custom designed high-volume, high-flow air cleaner, with billet backing plate, patented snap-in venturi, a pair of highly polished Power Vents and all necessary mounting hardware.
Depending on your preference and application, you can run the factory cover or one of Doherty's custom air cleaner covers. Power PACC kits are available for all '92 and later Evolution, Sportster and Twin Cam 88 models, fit with Keihin, CV, S&S E or G, and Mikuni flat side carburetors as well as Delphi injection.
When you consider the benefits, it's one of the most cost-effective ways to sharpen up your engine's throttle response while increasing usable power from the bottom end through peak output. It's the real deal!
