You’ve already read my article, Forced induction 101: Superchargers and turbochargers. Haven’t you? Go ahead, read it now. I’ll wait.
Last time, we covered the general concepts behind forced induction. Today, we are going to look at how superchargers and turbochargers use different methods to address the same problem. Basically, both types of -chargers are fancy air compressors (interestingly, the German word for supercharger is kompressor, so if you see a Mercedes-Benz with this word on it, or a letter ‘K’ somewhere in the name, you can guess what you will find under the hood). Air compressors, of course, need to be powered by something. What this something is is the main difference between the two types of forced induction.
Okay, I’ll spoil the suspense: superchargers are run by belts; a turbocharger is a windmill.
In case that’s not completely obvious, I’ll explain further.
Both superchargers and turbochargers compress air by means of little spinning blades. Kind of like a fan: it spins and blows air. Forced induction systems are tiny, fast, powerful fans, pointed into an engine.
Superchargers
Superchargers generate this spinning by means of a belt and pulley system attached to the front of an engine. You stick one pulley on the front of the engine, attached to the already spinning crankshaft, another pulley on the supercharger, and you run a belt between the two. This is a great system because the speed of the supercharger is directly tied to the speed of the engine. The faster the engine runs, (i.e. the harder you put your foot down) the more boost you get out of the supercharger.
The downside of this system is that it takes some of the power of the engine to operate the supercharger. It is less efficient than turbocharging, which I will go into in a moment. You might spend 10 horsepower to run the supercharger, but gain 70 horsepower from it running for a net gain of 60. The upside is that the extra power is always right there. The supercharger operates at all RPM levels and there is no such thing a turbo lag.
Turbochargers
The way I like to think of turbochargers is as windmill-powered fans.
Do you remember those brightly coloured pinwheels of your youth? You would blow on them and they would spin? If you built one of those out of metal and stuck it in the exhaust tubing of your car, you would have half a turbocharger. The exhaust gasses flow past and push the blades, creating a spinning motion. You then attach an identical, but backwards metal pinwheel to the other end of the first. This one is pointed into the engine and blows fresh air, rather than being blown by exhaust. That is what a turbocharger is.
The advantages of this system are that it takes almost none of the energy of the engine to run, so it is very efficient. Furthermore, since the system runs off exhaust gasses and helps the engine generate more exhaust gasses, the levels of boost that can be made with a turbocharger are very high. It sort of feeds itself into ever higher levels of boost.
Tune in tomorrow for part three of this (probably) three part series, where we will continue to look at turbos and superchargers, decide which is better and figure out what ‘intercoolers’ and ‘blow-off valves’ are.
