You've heard the word "turbo" tossed around a lot, especially by
performance car enthusiasts. But all you know is that it means an engine
has more "oomph" to it than normal. But what exactly is going on
underneath that hood? Let's open it up and take a look.
It's All About Better Combustion
Before you can truly appreciate what a turbocharger does for an engine, you need to understand the basics of internal combustion.
Internal
combustion engines are "breathing" engines. That is to say, they draw
in air and fuel for energy. This energy is realized as power when the
air-fuel mixture is ignited. Afterward, the waste created by the
combustion is expelled. All of this is typically accomplished in four
strokes of the pistons.
What a turbocharger
does is to make the air-fuel mixture more combustible by fitting more
air into the engine's chambers which, in turn, creates more power and
torque when the piston is forced downward by the resulting explosion. It
accomplishes this task by condensing, or compressing, the air molecules
so that the air the engine draws in is denser. Now, how it does that is
the real story here.
A Tale Of Two Wheels
A Turbocharger
is basically an air pump. Hot exhaust gases leaving the engine after
combustion are routed directly to the turbine wheel side of the
turbocharger to make it rotate. That turbine wheel is connected by a
shaft to a compressor wheel. As the turbine wheel spins faster and
faster, it causes the Compressor wheel to
also spin quickly. The rotation of the compressor wheel pulls in
ambient air and compresses it before pumping it into the engine's
chambers.
As you may have guessed, the compressed air leaving the
compressor wheel housing is very hot as a result of both compression
and friction. So what's needed is a way to cool that air down before it
enters the chambers. That's where a charge-air cooler (or "heat
exchanger") comes in. It reduces the temperature of the compressed air
so that it is denser when it enters the chamber (heat causes things to
expand, as we all learned in science class). The charge-air cooler also
helps to keep the temperature down in the combustion chamber. All
together, the engine, turbocharger and charge-air cooler form what is
known as a "charge-air system".
Some systems also include a tip
turbine fan which draws air across the charge-air cooler to further
reduce the temperature of the compressed air generated by the Turbocharger.
Not As Easy As It Looks
The
basic principal behind turbocharging is fairly simple, but a
turbocharger is a very complex piece of machinery. Not only must the
components within the turbocharger itself be precisely coordinated, but
the turbocharger and the engine it services must also be exactly
matched. If they're not, engine inefficiency and even damage can be the
results. That's why it's important to follow correct installation,
operating and preventative maintenance procedures.
