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Superchargers 101
Superchargers 101

By: Joel Justus – Performance Specialist

Superchargers are becoming more and more popular these days, both with OEMs and on the aftermarket.  Mostly because it’s a cost-effective way to “boost” (pun intended) performance of an internal combustion engine while still maintaining drivability.  Although there are different designs, they all operate on a pretty basic theory, giving you the reliability and performance that you’re looking for.

First, let’s look at why superchargers work so well.  An engine is essentially a self-powering air pump- the more efficiently the air can get into and out of the engine, the more power said engine will produce.  On their own, they have to suck air into some cylinders by moving the piston down in the bore, which is made possible by combustion in other cylinders providing the energy to keep them moving.  This is why engines produce vacuum, and why we look at vacuum when tuning or assessing health of an engine.  When a supercharger is added, the rotation of the engine not only moves the pistons up and down in their bores, but it also turns an air compressor (the supercharger itself), usually via a belt.  When this compressor is plumbed into the intake manifold of the engine, said engine no longer needs to suck in its own air- it is now essentially being force fed its air.  Since the aforementioned combustion requires air, fuel, and spark to happen, there is now a lot more air to make this happen.  Give that extra air additional fuel, and introduce that spark, and this party has suddenly gotten pretty lively!

Now that you have the “why”, let’s take a look at the “how”.  There are a few different “how’s” in this case, but to keep from getting too long winded, we’ll break it down into two fairly broad categories: centrifugal and screw-type.  I will break them each down separately.

Centrifugal superchargers are basically a belt-driven turbo.  The engine belt turns the impeller by means of a small gear reduction box.  The design of the impeller on this style of supercharger is very important to the efficiency, and therefore its power output, just like it is on a turbocharger.  These mount on the front of the engine similar to things like your alternator or air conditioning compressor, and connect to the engine with a series of tubes. 

The other style of supercharger is a screw-type supercharger, or “roots” style.  In this case, the belt turns essentially a long gear, or screw, which turns its partner gear, using that to compress air much like a typical oil pump.  This style mounts on top of the engine, in place of the intake manifold, so the only tubing used is before the air is compressed.

Each design has its own advantages and disadvantages, so what will work best for you will really depend on how you want to use your car, and like everything else in this hobby, every enthusiast has their own preference.  One of the biggest things to look at is heat.  Horsepower makes heat, so the more power that you make, the more heat you also make, regardless of whether you use a supercharger or not. 

However, this is magnified when using a supercharger, because compressing the air also has the byproduct of heat production.  We fight this using intercoolers.  These days, it’s common for the screw type blowers to have one or two smaller “bricks” internally- tiny radiators that the air passes through prior to entering the engine.  These bricks have coolant running through them, and in order to extract some of that heat out of the air charge.  These are known as air-to water intercoolers, since the air is cooled by a liquid. 

Centrifugals typically use an air-to-air intercooler.  These look similar to a small radiator, usually mounted in front of the engine radiator.  The air charge is pumped through the intercooler before it is plumbed into the vehicle’s throttle body.  While both have their limitations and their strengths, the best method really depends on how you will be using your car.

If this has gotten you really “charged” up, give us a call.  We would be happy to chat with you about your vehicle, and work on putting together a package that will fit your individual needs.  We work with a number of different manufacturers, so we are sure to be able to fit your needs and push you back in your driver’s seat.