Turbocharging Basics

There are proven ways to generate more horsepower with any given engine. One way is to make the engine bigger. While this is the most obvious path, it also has its disadvantages, painfully evident while filling up the fuel tank. Another way is to increase the volumetric efficiency of the engine, and spin the heck out of it in order to get more fuel and air into the cylinders. This is a fine way to go about making more power, but usually involves spending a pile of money on connecting rods, pistons, and cylinder head work. Also, the strains placed upon these various parts are increased along with the rpm.

Turbo Differences
One more way to get more air and fuel into the cylinders without spinning the engine faster or making it bigger is to force more fuel and air into the engine by way of forced induction. This method crams more air and fuel into a given space by way of a supercharger or turbocharger.


While a supercharger and a turbocharger both end up accomplishing the same task of forcing more air and fuel into the engine, they go about it in different ways. A turbocharger runs off engine exhaust. It utilizes energy that would otherwise go wasted out of the tailpipe to compress more air and fuel into the cylinders. A supercharger uses power directly from the engine via belts and pulleys to do the same thing. In theory, a turbocharger is more efficient than a supercharger since it doesn't take power directly away from an engine. Instead, a turbocharger utilizes power that would otherwise be wasted out the exhaust.

Induction Happens
There are two finned wheels inside the turbocharger that allow forced induction to happen. The turbine wheel lies in the path of exiting engine exhaust. The more exhaust that hits this wheel, the faster it spins. Connected directly to the turbine wheel by way of a shaft is the compressor wheel. The compressor wheel takes incoming air and forces it along with a greater amount of fuel into the engine. The more air and fuel entering an engine, the more power it makes.


More power increases the velocity of the exhaust. This exhaust makes the turbine wheel spin faster. As the turbine wheel spins faster, so does the compressor wheel. And so on. Thus, a turbocharger can be used to extract a great deal of power from an engine of small displacement. WRC rally cars use turbochargers to produce 400 horsepower from an engine with a rules-dictated displacement of two liters. Think about that the next time you pick up your favorite two-liter bottle of soda—400 horsepower from two liters.