Types of turbos

First of all, there are many different kinds of superchargers. They all have two things in common:

1) they compress air into the intake manifold, just like a turbo

2) they are belt-driven, not exhaust-driven like a turbo.

The differences between blowers is mostly how they compress the air. The most popular design is currently the centrifugal supercharger. These build boost proportionally with RPM. The faster the engine spins, the faster the blower spins, and hence the more boost that the blower makes. These obviously make the most boost at high RPMs, unlike the Bell supercharger which has a more flat boost curve, but apparently makes less boost at high RPMs. Anyway, superchargers have two advantages over turbos:

1) they make boost quicker, since there is no need to wait for the exhaust to speed up and spin the turbo

2) they are often simpler setups, since there is less plumbing

No need to drive the blower with exhaust gas when a simple belt will do, and the Powerdyne unit does not even need any oil lines to it, since it is self-lubricated. However, turbos have three advantages

1) they don't steal energy from the engine to compress air. As RPM goes up, a blower takes more and more power to run, and its efficiency consequently suffers. For a turbo, no parasitic power loss means more power to the wheels.

2) Unlike a centrifugal blower, a turbo can build full boost at a much lower RPM, especially for a high-RPM engine. You don't have to wait until 8K RPM for full turbo boost.

3) A centrifugal blower makes boost according to RPM, regardless of throttle position. But when you are not standing on the throttle, the turbo does not build boost, so you save gas, relatively speaking. But then again, who would buy a turbo and not stand on the throttle?

(Powerdyne Supercharger)

The Difference Between a T25, T3, T4, and T3/T4

These are some of the different turbine configurations that you can get in your turbo setup. To give a basic explanation, they describe the size of the "paddle-wheels" that run the turbo. Bigger wheels take longer to spool up, but produce more boost when they finally do. Among the ones listed above, the T25 is the smallest, and the T4 is the biggest. Race applications generally take larger turbos than street applications. The T3/T4 is called a "hybrid" between a T3 and a T4. A T3/T4 hybrid uses a T3 turbine wheel and a t4 compressor wheel, so that it spins up faster than a T4 but makes more boost than a T3. A T2/T3 hybrid is the same, but smaller. Almost all turbo kits currently use the T3/T4 unit, which has been used successfully on the 1/4-mile strip in many drag race events, but a smaller unit may be better suited for milder street applications that don't require more than 10psi boost. The T3, T4, etc. are Garrett turbos, which are currently the most popular turbo manufacturer.

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