Blowing Cold Air: Comparing Superchargers

Procharged MustangYou may have heard this comparison before: ProCharger vs. Supercharger. Depending on your car scene, that may launch an ongoing argument about what defines a supercharger as opposed to other types of forced induction. More importantly, if you’re deciding on what type of blower to purchase, knowing the pros and cons of each option can make a considerable difference. To help, here’s a quick breakdown of the three most popular types of superchargers: roots, centrifugal and screw types.

Roots Superchargers

Virtually all types of forced induction operate under the same principal: shoving as much cold air as possible into each cylinder. Since air increases in density as temperature drops, colder air results in a more powerful combustion. While turbochargers operate off of exhaust gasses, superchargers take a different approach. At the most basic level, two types of superchargers exist: positive displacement (roots) and those that aren’t (centrifugal and screw).

Fundamentally, roots superchargers act as air pumps instead of compressors. This means that positive pressure is put on the engine from the first inch of throttle movement. When metal meets carpet, a roots blower will give everything it has regardless of RPM. That results in boost throughout the rev range and provides enormous potential for power gains. Additionally, reliability is strong and, if we’re honest, these types of superchargers look amazing. The blower you see sticking out of the hood of an 800+ hp muscle car? That would be a roots type.

Of course, there are some downsides. Chief among them are lengthy install times (pretty complex equipment) and increased operating temperatures. Throttle response will also become far more instantaneous, which may take some adjustment.

Centrifugal Superchargers

Unlike a roots blower, which is essentially a pump, a centrifugal supercharger is a dedicated compressor. In fact, it looks nearly identical to a turbocharger. Just like a turbo, an impeller inside the supercharger compresses the air, which is then delivered to the engine by way of a scroll. The key difference here is that a centrifugal supercharger is belt driven, as opposed to turbochargers, which are fed off of exhaust gasses.

Which is preferable? Though it’s somewhat stereotypical, it generally holds true that turbos offer greater potential for power gains, while centrifugal superchargers deliver more controllable power delivery and a more linear torque curve. They also provide lower operating temps, greater adjustment options than roots superchargers and far easier installation. The downside: decreased low RPM torque when compared to roots blowers.

Also, just to settle any ongoing debates, a ProCharger is a centrifugal supercharger, not a combination of types or a different one entirely. It’s a matter of effective branding, not the supercharger composition itself. Sort of the same way you might say Kleenex to refer to tissues in general.

Screw Type Superchargers

Though they look very similar to roots superchargers, screw types are air compressors rather than pumps. By using twin screws to compress air, power levels can nearly match the potential of roots blowers without the significant heat. However, the downsides are more prominent. It’s difficult to significantly increase boost levels, the power curve stays flat at low RPMs (not much to give up high) and installation remains quite demanding. On a positive note, reliability is strong and power increases can be dramatic at the low-end of the rev range.

Which Is Best?

It really depends on what you plan to do with your build. For maximum power regardless of any compromises, roots is your go-to. For a daily driver with occasional track use, centrifugal could be the way to go. Plan on bulking up the low RPMs for heavy-duty towing? It’s hard to be screw types. The Goldilocks solution for most drivers likely is the centrifugal supercharger, but ask around your local car community to see which types best match your engine and build goals.

Have questions about supercharging or want to share your own advice on various types? Let us know in the comments below or via our Facebook and Twitter channels.

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