Quote Originally Posted by nova_robotics View Post
snip ... Other than for being awesome and crazy, having multiple superchargers in parallel is a bad idea. You can make far more power by putting them in series with intercoolers between them (if space allows). Lets say you want to make 30 PSI of boost. Two compressors in series with an intercooler between them takes far less power to drive than a single big compressor, both systems making the exact same 30 PSI...
Some guys who put blowers on hotrods don't even have the rotors in them. Some will use an old damaged blower housing with a pulley on it just for visual effect. They certainly do not need the extra horsepower, as there is no way to use it.

If you really wanted to make a QUICK and FAST hot rod, you would not put two engines in it. One of those engines, properly built, unsupercharged, in an identical hot rod, could blow the doors off of that two engine rod. As shown it is eye catching, clever, well built, I am taking nothing away from it.

There are many reasons hot rods are built, many are just a very cool form of visual art, expressing their makers imagination and fabrication skills, rather than a exercise of applying the laws of physics.

In regard to parallel vs series. There is a lot of physics involved in that. Compressors in series can create more pressure, up to the pressure limit of the last compressor. But, if the compressors are identical, the second compressor has to be driven at a higher speed in order to further compress the gas coming from the first. As you know, each succeeding cylinder in a multi stage unit is smaller than the proceeding one. But the compressor can move no more air than passes through the first stage.

If one compressor can create the pressure you need, in order to make more volume, you connect them in parallel. I have used 3 compressors in parallel to generate enough volume for a sand blasting job. Connecting them in series, they would not be able to generate the volume needed at their maximum pressure. I admit it probably did use more power than having one compressor large enough to create the same volume.

In your example, connecting them in series, even driving the second one faster as required, would not generate as much volume at 30 PSI as driving them in parallel, each at 30 psi (2.68bar).