Superchargers
Superchargers have become as standard as high-flow air filters in the
aftermarket world. Their like-factory easy installation and reliability,
improved fuel economy, and huge power increases, have made even the car makers
take notice by offering them as standard equipment on many factory vehicles.
When you begin to search for the best supercharger for your vehicle, the choices
can sometimes seem overwhelming.
A supercharger is essentially a large pump that compresses air and forces it
into the engine's air intake. Turbochargers do the same thing, only they are run
by exiting exhaust gasses, while superchargers are powered by the engine's
spinning crankshaft, normally via the accessory belt. Originally built for World
War II aircraft, superchargers have become very common in today's performance
automotive world, and featured as original equipment on some new sports cars
straight from the factory!
Superchargers have become popular in recent years for several reasons, including
cost efficiency, reliability, and of course, performance. Supercharging an
engine often results in huge power increases in the range of 50% to 100%, making
them great for racing, hauling heavy loads, or just having fun in your daily
driver. Although superchargers carry a fairly high ticket price when compared to
other single performance upgrades ($1500 - $4000), nothing provides more
horsepower for your dollar... in fact, nothing even comes close. And because of
the way superchargers work, they provide power only when the engine is under
full throttle or under load... not under normal cruising conditions. This means
that the supercharger will not affect the engine's reliability, longevity, or
fuel economy under normal driving conditions.
The twin-screw supercharger was originally invented in the 1930's by Mr. Alf
Lysholm who was then Chief Engineer of SRM (Svenska Rotor Maskiner AB). The
twin-screw design was developed to fill the tremendous voids the centrifugal,
turbo and roots superchargers have. This concept was intended to meet the
requirements of a high average efficiency under most varied conditions of
pressure and speed, a high maximum efficiency - preferable above 85% - with
small bulk, low weight and also suitable for direct drive. This concept lead to
the development of the twin-screw supercharger which was compact and light, had
a very high efficiency over almost all varied conditions of pressure and speed,
and an incredibly high maximum efficiency. This concept became a reality in the
late 1930's and early 1940's when the Lysholm twin-screw supercharger was
produced. Because of high building cost, the screw compressor did not find its
way to OEM use on internal combustion engines, but industrial applications for
air compressors.
The roots style supercharger is the oldest type of supercharger and dates back
to the early 1900's when it was first used as an industrial air-moving device.
In the past 30 years or so, however, the roots style supercharger has undergone
drastic changes and has become so efficient and quiet that it is now commonly
used as a forced induction system for automotive applications. The roots style
supercharger, while still the least thermally efficient supercharger design
(versus centrifugal and screw-type designs), has found a home on board top fuel
dragsters as well as on modern Mercedes, Ford, and GM passenger cars as an
original equipment power adder.
How it Works
The roots type supercharger is known for its ability to produce large amounts of
boost while spinning at very low speeds. On an automotive application, a roots
type supercharger can often make it's full (peak) boost by 2000 engine rpm. This
characteristic has contributed to its success and popularity on the top fuel
racing circuit and has made it ideal for use on smaller 4 and 6 cylinder engines
that traditionally struggle in the lower half of the rpm range (and is why
Jackson Racing uses a roots type Eaton compressor). Another advantageous
characteristic of the roots type supercharger is its simplicity of design. The
roots type supercharger has very few moving parts and spins at low rpms, making
it one of the more reliable and durable supercharger designs.
The big disadvantage to the roots type supercharger is its thermal inefficiency
- or its nature to produce high discharge temperatures - which robs power from
the engine. With a roots type supercharger, an intercooler is almost always a
necessity to bring the air charge temperatures down to an acceptable level. This
poor thermal efficiency can be attributed to the fact that it has no internal
compression (compression is done after the air leaves the discharge port).
Additional heat is created by compressed (hot) air that leaks backwards past the
rotors and heats up the temperature of the inlet charge.
Monaro & GMH & GMC CARS forum
monaro & GMC & gmh CARS, This group has been set up to provide a platform for
anyone interested in monaro & GM CARS, to post comments or questions regarding
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F100 ROVER SD1 MGB V8 Gas turbine
The Illawarra SS ORONTES monaro GMC GMH
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