If you’ve read my article ‘Forced Induction 101: Superchargers and Turbochargers’, you know what forced induction is. If you’ve read “Forced Induction 102: Differences in forced induction systems” you know how superchargers and turbochargers are different. If you’ve read neither, why not? You have something better to do, or something. You could probably read this article without reading the two previous, but why would you want to?
Last article, we discussed the differences between the two systems, but which one is right for you? Well, that depends on what you want out of your car.
Because of how they work, their efficiency, and the levels of boost they can generate, if you actually intend to race your car, or if you are only concerned with the horsepower figures, the obvious choice is the turbocharger. The peak amount of power you can get out of a turbo dwarfs the peak of what you can get with a supercharger. However, there is also the problem of turbo lag.
Since turbos run off exhaust gasses, there is a minimum amount of these gasses required for the turbo to spin. If your engine is running at low RPM, the amount of gasses generated might not be enough to spin the turbo and generate boost. For example, no turbo will generate boost with the engine at idle speeds. This makes sense. You have no need for boost while the car is standing still. The time period after you start accelerating and before the turbo kicks in is referred to as ‘turbo lag’. The bigger the turbo and the more boost it makes, generally, the more turbo lag. With some engine-turbo combinations and depending on how you drive, you might never actually get to use the turbo at all.
Superchargers, on the other hand, deliver boost no matter what the speed of the engine. They are running, even at idle, when the car is stopped, and will kick in immediately. You will get use out of a supercharger, no matter how you drive.
For a daily driver with a good amount of pep under the hood, a supercharger is probably better. For a race car, you want turbos.
Blow-off valves and Intercoolers
Two components that go along with any system of forced induction are the intercooler and the blow-off valve.
Intercoolers address the problem of heat. Superchargers, and especially turbochargers generate a lot of extra heat in an engine. It is the simple side effect of compressing air and the existence of friction. Intercoolers cool down air after it leaves the turbocharger, but before it enters the engine. This does two things it 1) prevents the engine from melting and 2) allows you to run higher levels of boost without worrying about the engine melting. Cold air is also denser than hot air, so intercoolers increase the boost effect of forced induction.
Blow-off valves are neat. Not just because of what they do, but because of how they sound. Blow-off valves have a very distinct whistle. Sometimes, forced induction systems make too much boost for the engine to handle. This is more of an issue with turbos than superchargers. So, to get rid of the extra pressure (that would harm the engine) the blow-off valve was invented. At a certain amount of pressure, the valve will open, releasing the extra pressure. The value of blow-off valves, aside from the engine preservation, is that, when you step on it, the whistle will alert anyone around to the fact that you have a turbocharger. Since turbo cars are more expensive and faster than other cars, I think that turbo whistle should be considered a status symbol.
I hope you enjoyed this three part series on forced induction. Until next time, drive safe.
