A turbocharger is a small compact unit which is used to
compressed air before entering the engine. This increase
in air density enables the engine to burn more oxygen and
fuel on every power stroke which produces more power yet
retains and often increases fuel economy. A turbo offers
a massive improvement in engine performance without adding
significant addition weight or compromising reliability.
Forced Induction
A turbo diesel car uses forced induction to increase air
intake, enabling the engine to develop significantly more
power. The increased performance of turbo diesel cars is
also matched with similar or better fuel economy than non
turbo charged engines.
Driven by hot exhaust gases which exit the engine, a turbocharger
utilises wasted energy to drive its spindle and compress
air within the engine's air intake. Superchargers however
are not driven by exhaust gases but actually draw engine
power and are directly driven by a belt.
Turbo Boost & Turbo Lag
There are several terms associated with turbochargers.
Boost describes the amount of extra power felt when the
turbo is supplying a flow of compressed air into the engine.
Turbo lag describes the time delay experienced between depressing
the accelerator and when the turbo boost is felt. Exhaust
gases must first build to a sufficient level to power the
turbo, enabling it in turn to compress air to feed the engine.
Turbo lag and boost have been area of recent dramatic development.
Engineers have managed to reduce turbo lag by lightening
the turbo spindle, hence reducing its inertia, and smoothing
out turbo boost to supply a constant flow of extra power
rather than a short sharp spurt.
Turbo Cool Down
One important consideration when driving a turbo diesel
car is to ensure that the engines turbocharger is allowed
to cool before switching off the ignition. This is especially
important after a fast drive because the turbo, heated by
hot exhaust gases, can easily overheat surrounding engine
oil. The turbo relies on engine oil both as a lubricant
and as its fluid bearing on which it spins.
Many modern new breed turbo diesel cars such as the Peugeot
HDI, Citroen HDI, Ford TDi & TDCi, Volkswagen TDi and
the Vauxhall CDTi, provide an exceptional combination of
economy and performance.