How Car Parts Work: Roots Supercharger

There are 3 types of superchargers: Roots, twin screw and centrifugal. All these 3 superchargers employ different methods and designs to compress and supply air to the intake manifold. In this article, I will explain the working of a Roots supercharger.

Roots Supercharger:

Roots supercharger is the oldest model of all the three superchargers. It was designed by Philander Roots and Francis Roots and patented it in the year 1860. It was initially used as an air pump for industrial applications. It is also called as Roots blower. In 1900, it was first used in a patented design engine by Gottlieb Daimler.

Design and Working:

Roots supercharger consists of a pair of (two or three lobe) rotors. The 2 counter rotating rotors are intermeshed with each other in a compressor casing. The two rotors trap the air coming in from the intake port between the lobes and push it against the compressor casing as they rotate towards the discharge port. During each rotation, a specific amount of air is trapped and moved towards the discharge port.

One of the characteristics of a Roots supercharger is that the air is not compressed between the lobes when it travels from intake port to discharge port. Air is compressed only from the point of discharge where the air is exposed to high pressure.

It is common to find a Roots supercharger equipped with an intercooler to cool down the compressed gases. It can provide efficiency up to 70%.

Advantages of Roots Supercharger:

· It can provide large boosts even at lower engine rpm.

· Boost is provided throughout the entire rpm range, right from idling speed.

· Simplicity of design

· It is more reliable and has very few moving parts.

Disadvantages:

· High air discharge temperature, making it thermally inefficient. Intercooler is a must to bring down the temperature.

· No internal compression. The air is compressed only after it is discharged.

· Lower boost pressure at higher rpm.