Back Induction Belt-driven Practicalities What's it like Advantages Disadvantages Picture
We’ve all heard the name supercharger or compressor right ? What do they actually do and how do they work ? Read on and find out more …
In terms of creating extra power the supercharger works in much the same way
as the turbo (see our turbo article) being a device to create forced induction
and ram more air into the engine. The way it differs from the turbo however is
in the way the device itself is driven.
Top
The impeller in a turbo is spun using gases from the exhaust of the engine,
the supercharger is driven using a belt connected usually to the crack shaft of
the engine. This means that the supercharger is running (spinning) the whole
time, so air is being driven into the engine all the time the engine is turning.
The result is no lag like you would get with a turbo. Awesome! I can hear you
say, surely that’s the ultimate forced air induction system ? Well not quite
because like all things in life nothing comes for free and nothing is perfect
and there is an overhead to this which comes in the way of friction. Because the
engine is running belts to run the supercharger this is a drain on power so
where the turbo increases the efficiency of the engine as a system the
supercharger is decreasing it. Of course the gains in power are far greater than
the losses due to running the supercharger but the gains are not delivered as
efficiently as they are with a turbo.
Top
The supercharger is used extensively in the world of drag racing and custom street machines where acceleration from the word go is of total importance making the supercharger far more useful than the turbo. Some of the huge superchargers used on dragsters can take 500bhp from the engine to run them and they can add more than 2000bhp to the output ! On a road the are seen less often perhaps due to the efficiency of the turbo and I have heard reports of superchargers suffering from long-term fatigue needing expensive rebuilds after relatively few miles.
They are not as easy to tune as a turbo either because to alter the amount of
boost being created requires the supercharger to run faster or slower which
requires pulleys to be changed. Extreme applications use Kevlar belts because
belts can snap or melt in some cases. On drag cars they certainly do look
impressive though and on road cars they are generally compact making them nice
an easy to fit within the engine bay tidily.
Top
If you take a normally aspirated engine and add a supercharger it would
retain the same torque curve. This means that cars with superchargers actually
feel the same to drive with the same engine characteristics only with improved
power across the rev range giving better acceleration and top speed.
Top
No lag. They make a lovely whistling noise. They increase power.
Top
The power is delivered at a price (bhp). On a road car they can can need expensive rebuilds. Not as easy to tune as a turbo requiring pulleys to be changed.
It’s not easy to understand why they are not seen more on road cars,
certainly on applications such as the Mercedes SLK Compressor and the VW Golf
G60 they were well respected and kits are readily available for many cars
allowing them to be bolted on. They can be retro-fitted to many cars and often a
supercharger will run relatively low boost giving a good power gain across the
board but without the need to modify the internals of the engine to cope with
increased internal pressure. Who knows, they could be the next big thing.
Top
Back Induction Belt-driven Practicalities What's it like Advantages Disadvantages Picture