At the heart of the turbocharger are the turbine and compressor which rotate together on the same shaft. The turbine is housed in and driven by the exhaust stream. It turns the compressor which pumps air into the engine.
Critical attention is needed to the design of the centrally mounted bearing, because the turbine, compressor and shaft can rotate at speeds of up to 200,000rpm.
There are two main ways to get more power from a car’s engine. The first
(and until recently the most popular) is to increase the capacity of the
engine. The second is to increase the amount of fuel/air mixture going into the
Generally, the more fuel/air mixture going into the cylinders, the more
power the engine will produce. So part of the solution is to tune the
carburettor, cylinder head and manifolds to allow the engine to `breathe’ more
freely, but there are limits to how much power can be extracted from an engine
by these means while at the same time maintaining the engine’s reliability and
An alternative way of getting more fuel/air mixture into the cylinders is
with a turbocharger.
Racing with turbos
Unlike road cars, racing car engines do not have to compromise between
power and flexibility, so they can be tuned for ultimate power at high revs
because this is the speed range where they will spend most of their time
With a turbocharged engine, this inevitably means running the engine at
very high boost pressures as well as carrying out conventional tuning
The most powerful turbocharged race engines can cope with boost
pressures of 4-5 bar (60-70psi), whereas a turbo road car will run at a
maximum of about 0.7 bar (10.5psi).
What is a turbo?
A turbocharger is basically a pump driven by the exhaust gases passing out
of the exhaust manifold. The unit consists of a wheel with vanes – the turbine
– that fits inside a housing in the exhaust system. From this turbine a short
central drive shaft runs to a similar vaned wheel called the compressor that
feeds into the engine’s air intake.
When the exhaust gases flow
from the engine, they spin the turbine, which in turn spins the drive shaft
to turn the compressor. So, when the engine is running, the exhaust gases drive
the turbine which makes the compressor pump air into the engine.
A fixed amount of fuel is automatically sucked in with the air if the engine
has a carburettor. If the engine has fuel injection, the computer control unit
is programmed to suit the boost pressures.
The faster the engine is running, or the larger the throttle opening or
both, the faster the turbocharger will spin. The faster the turbo spins, the
more pressure, or boost it develops and the more air it forces into the engine
to create more power.