Electric Superchargers vs. Belt-Driven Blowers: Who Wins?

March 30, 2017

Electric Supercharger Belt-Driven Blower

One can increase the flow rate of a fuel-air mix to the cylinders by using an electric supercharger. For years, auto engine designers have known that there are two ways of increasing the output of a powerplant. The other is to increase the specific size and number of pistons in the engine. There are two types of supercharging available today, one passive - turbosupercharging, and the other active - active electric or belt-driven supercharging.

The History of Supercharging

For nearly a century, engine designers have known that if you increase the density and pressure of the fuel-air mix that is delivered to a cylinder, you will increase the power output of that cylinder. The obvious way of achieving this in the early part of the last century was by adding cylinders to each engine, and by increasing the compression ratio of each cylinder. Once the number of cylinders was increased to eight, (the maximum number used for many years in many vehicles in a V configuration,) the way that the fuel-air mix was pumped up was by adding extra barrels to the carburetor in a normally aspirated engine. The maximum number of barrels per carburetor was usually four ,and in some very high performance vehicles you could have as many as four carburetors feeding the engine.

Engine Power Reaches a Plateau with Standard Carburetion

By the end of the 1960s, this concept reached a plateau. One could only increase the number of carburetors to a maximum of four on an eight-cylinder engine used in a standard street-legal vehicle (each carb was feeding two cylinders). Some racing models used one carb per cylinder, but the problem was that one ran into the plateau, as engine designers were reluctant to increase the compression ratio of the cylinders. This is because it would have increased the weight of the engine, defeating the purpose of the compression increase. Direct fuel-injection was also tried, to increase the power output. While it did succeed, this concept also plateaued. It was about 1940, and this concept was plagued with many bugs.

The Drive Debate: Direct Drive Versus Turbo Supercharging

Direct or mechanical supercharging, while it did increase the power of the engine, did extract a penalty. It took between two and five percent of the newfound power to drive the supercharger, so although the net gain was positive, there was a negative side in that it cost one fuel just to turn mechanical supercharger. A second school of designers realized that there was an untapped source of power for the supercharger. The engine exhaust; and so they built a compressor that sat on both sides of the engine's manifold system.

The Final Solution: The Electric Supercharger

By the end of the last century, it was beginning to look as if some order was finally settling in. Top fuel dragsters took the belt-driven blower to its ultimate extreme. Often extracting upwards of 1,200-horsepower or more from an engine. The cost, though, was enormous as large belts were used to turn not only the fan but also the blower (supercharger). It was then that a designer turned to the electrical system, where power was basically going to waste. The design was simple; use an electric motor to turn the electric blower. Now, engine designers could push well past the 1,200-horsepower limit imposed by belt-driven systems.

Creative Commons photos by Eadey and fred ross lord