If you're a regular Turbo reader, you're probably a fan of forced induction, most likely of the turbocharged variety. Turbochargers are perhaps the greatest producers of raw power due to their penchant for using waste energy to produce additional power. The turbo's pure efficiency of getting something for nothing is an irresistible draw to technical gearheads. Turbochargers have a history of making so much power that they're often either heavily restricted or outright banned in nearly every form of motorsports. As such, it's only fair that we give superchargers equal billing. Superchargers have many advantages over turbos, some obvious and some that require a closer look.
What Is A Supercharger?
To make power, an engine burns a mixture of fuel (usually gasoline) and oxygen in its cylinders. The heat and expansion created by this burning drive the piston and connecting rod downward, turning the crankshaft and making useable power. The supercharger uses a compressor that's driven directly off the engine's crankshaft to pressurize the intake air charge. By pressurizing the charge, density is increased thus increasing the oxygen content of the intake mixture. Since more oxygen is now being induced into the engine's cylinders additional fuel can be too. This denser mixture of fuel and oxygen releases more explosive power during the combustion event. Simply put, a supercharger is like stuffing a bigger engine into the same space occupied by something once smaller.
The Eaton supercharger's more efficient because, unlike classic roots lobed vane blowers, it has spiral vanes. The spiral vanes, when combined with carefully located and timed inlet and outlet ports, produce internal compression. The bypass valve and port shown here in the upper part of this cutaway allows air to recirculate around the blower at part throttle to cut pumping losses and improve fuel economy when cruising.
Although they generally cannot generate the raw power of turbochargers, superchargers are an excellent choice for a streetable power upgrade. One of the biggest advantages of a supercharger kit is that it is one of the largest power adders that you can buy and add to your car in a weekend. A bolt-on supercharger kit can add 40-150 whp at once. Although supercharger kits are relatively expensive, they are still a good bang for the buck when considering the power-adding factor.
It's Not Easy Being Green
Kermit used to bitch about this and so do many of those who opt for aftermarket turbo kits. The most-enticing thing about supercharging is the possibility of it being 50-state street-legal. A CARB-approved supercharger kit is probably the most powerful street-legal power adder one can get. Period. Supercharger kits are easier in terms of passing emissions tests when compared to turbo systems because they don't affect the light-off time of the catalytic converter after cold starts. Turbos place turbine blades and exhaust housings, essentially a heatsink made of cold iron, in front of the cat, delaying the exhaust heat transfer needed to kick off the essential pollution-eliminating oxidation-reduction reaction going on inside. Usually cats are lit off within 30 seconds of a cold-start but a turbo can easily quadruple that time. As 90 percent of a vehicle's total emissions are created in the cold-start part of the federal emissions drive cycle, this seemingly small delay has a huge effect on the total overall emissions output during certification. Because many supercharger kits on the market are either CARB approved or are in the process of obtaining CARB approval, there is less hassle when it comes time to smog your car if your state is one that demands a visual inspection with your smog check. Even if you only have to pass a tailpipe smog check, a supercharger affects emissions less than many other mods. In this age of regulation, this is a significant advantage.