![ProCharger](images/DailyArticles/December2009/ProCharger/ProCharger-Lead.jpg)
Supercharging a Harley
Story by Buck Manning, Photos courtesy of ProCharger
Bolt-on products for your Harley are all the rage these days. But if you’re interested in making some serious power, bolt-on performance pieces are not going to up the ante unless you do some serious internal work along with a complete replacement of basically everything from the engine block up. This is not only very costly, but usually involves some serious downtime and prolonged break-in procedures. Bolting on a forced-induction system like ProCharger’s Centrifugal Supercharger is the V-twin equivalent of a fast-food drive-thru with super-sizing mandatory. In typical American style, there’s immediate gratification with little waiting.
I figured going straight to the horse’s mouth for a bit of wisdom was the first logical step and luckily I hooked up with ProCharger’s Senior Performance Technician Sergio Shifman. He explained how ProCharger approached the idea of bolt-on inter-cooled centrifugal superchargers for V-twins after being successful in the auto end of things. “Coming into this, a lot of guys from the bike side hadn’t heard of us so we wanted to be careful to make sure we didn’t show it as a complete alternative to engine building, but it can be because of the dollar per horsepower benefit. But, I’d say personally, the best reason to go with the supercharger is that you keep the reliability and tame low-compression/mild cam characteristics of a street motor with the big horsepower of a radical big-inch naturally-aspirated motor when you need it.” Sergio further explained, “ When you’re just cruising in traffic or part-throttle putting around, the motor is at the same point a mild compression/small cam motor is, running fairly cool and real tame. When you ‘re in the throttle heavy and want power, that’s when the boost comes in and gives you the extra power. You don’t have the big, heavy heat of a 10.5 or 11:1 compression/big-cam motor all the time.”
In other words, let’s say you’re riding a ProCharger-equipped stock 96” dresser at around 2,500rpm and need to pass, as you twist the throttle according to Sergio, “There would be a 15hp gain over what the motor would make on its own. If you stay in it, the RPMs climb quickly and the horsepower gains keep getting bigger and bigger. By 3,500rpm, it’s going to make 25-30hp over what the motor would be making on its own and it just keeps climbing from there. It’s definitely an instant increase because the supercharger’s always spinning — it’s always moving more air. We claim a 50hp gain on a 96” Twin Cam, but that’s not 50hp right at the throttle, but a linear gain up to a 50hp increase by redline. We can make 120hp to the rear tire with a stock 96” motor with a good set of slip-ons.” Basically doubling the power to the rear wheel of a stock motor sounds like good clean dresser fun (with a touch of extra passing safety built-in) to me. But what if you wanted a bit more? “The cam can be a good, quick and easy upgrade. A Screamin’ Eagle 211 cam seems to be really, really good. It’s got a good duration split which seems to help boost flow through the motor a little better,” said Sergio. “It’s not always the best cam for a normally aspirated motor, but for a supercharged motor, it works really well. One of our dealers, Fat Baggers Inc., seems to do a 211 cam and their exhaust package with just about every ProCharger kit they install. They end up with 130-135 horsepower.” Hey, that’s even more “good clean fun” and makes getting a little down and dirty on the throttle a wee bit more exciting.
ProCharger’s kits include an air-to-air intercooler that boosts power over a non- intercooled setup and allows your engine to run cooler and better in the long and short run by reducing the temperature of compressed air going into your engine. “On an 80-degree day, you’re sucking in 80-degree air and the temperature of the air after it’s compressed to ten-pounds of boost is probably in the 170 to 180-degree range. If you force that hot air straight into the engine, you’re going to have to take away a lot of ignition timing or really add tons and tons of fuel to cool off that air, otherwise it will destroy the engine with detonation. The intercooler pulls about 70 to 80% of that heat out so on an 80-degree day, you’re probably pushing only maybe 100-degree air into the motor at full boost.” Sounds cool to me.
Speaking of heat, that’s one of the uncomfortable, constant by-products of a built-up normally aspirated engine. “When you’re sitting in traffic or just cruising down the street or down the highway at steady, moderate throttle, there’s no boost really being forced into the motor so there’s no gain in oil temperature,” said Sergio. “Under heavy load when there’s boost being forced into the motor, there’s more heat, but at that point you’re boogying down the road enough that it’s not a problem as the engine’s got a lot of air flow on it.” One other point that should be made is that the ProCharger supercharger does not share oil with the engine, but has its own supply of “really light” synthetic oil. “Having the oil separate for the supercharger keeps it from cross-contamination like from a dropped engine lifter or a spun bearing,” said Sergio. “We suggest changing it every other engine oil change. It’s pretty simple, got a drain plug at the bottom and you fill it up with one 2.5-ounce bottle of oil.” Four 2.5-ounce bottles come with every kit so you’re good to go for quite a while.
ProCharger has two types of kits available, a Full System that includes everything needed for EFI bikes including a DynoJet Power Commander for tuning and higher flow injectors while the kit for carb bikes comes with a Mikuni “Easy Fit” 42mm or 45mm mechanical slide carb to replace the stock CV unit (necessary for pressurized applications), a fuel pump, fuel pressure regulator and all the fuel lines needed. The Tuner Kits come without fuel injectors or tuning module and is geared to owners of very large displacement engines who have or need specific items for their own build. All kits come with complete instructions (54 pages with pictures) and Sergio added, “ It’s very thorough with a lot of good text. Most guys are going to their dealerships to have them put on and most of our dealers are Harley-Davidson dealers. We don’t discourage people from installing it themselves and it doesn’t change our warranty if you do it yourself. A competent do-it-yourselfer should be able to do it in six hours. If you need help, our tech line is open 8:30 to 5:30 Central Time Monday through Friday.”
If a one-day hop-up of your Twin Cam to double the stock rear wheel horsepower power with no pesky problems like starter motors that can’t turn over a high-compression engine or excessive heat roasting your chestnuts over an open fire sounds good to you, check out ProCharger’s website at www.procharger.com and maybe give Sergio a call too.