| The supercharger's
biggest benefit, torque, is the ideal upgrade to the A-Series motor. While
horsepower is typically achieved by increasing RPM, torque has been the
sole property of increased displacement. A V-8 has loads more torque then
a 4 cylinder, but the application of modern superchargers has greatly
diminished this distinction. Since all A-Series motors have 3 main bearing
cranks, they are best suited to lower RPM (less horsepower) and can take
advantage of the major benefit of superchargers- torque! Twin Screw
Compressor Design: The twin screw supercharger is actually a positive
displacement "compressor", not just a blower. This unique design
allows the Mini Spares Supercharger to force a greater volume of air, at
lower temperatures, into the manifold than "Rootes" design
blowers. Volumetric Efficiency (VE) measures how well a supercharger
breathes and how much leakage occurs. For example, if a supercharger has a
displacement of 10 liters and only 8.8 liters exit, the unit is 88% VE.
Naturally a less efficient supercharger with a lower VE will have to work
that much harder to produce sufficient air. The Mini Spares supercharger
;has an 88% VE, while most "Rootes" type blowers will produce
60% VE. Adiabatic Efficiency (AE), measures how well a supercharger uses
the energy delivered to the drive shaft and how well it controls
temperature from intake to exit. The low exit temperature of the Mini
Spares Supercharger, as referenced to intake temperature, precludes the
need for internal engine modifications or compression changes. The Mini
Spares Supercharger requires less power to turn its rotors, and condenses
the air to produce more cool air than normal blowers. Care and Maintenance:
All Mini Spares Superchargers are self-contained and require normal oil
level checks and regular lubricant changes. All gears and seals are
lubricated by design during operation cycles. Unlike the virtually all
turbochargers, no external lubrication system is needed. Like all of the
work we do with an engine, extreme care should be taken to insure a very
clean environment while installing, as the fine tolerances present in this
device will not tolerate dirt, grit or grime. In addition, the intake air
filter should be serviced at normal intervals. The Dyno... The Numbers
& What They Mean The facing chart shows the horsepower increases of
the Mini Spares Supercharger compared to their respective un-supercharged
counterparts. The stock 1275cc engine had 8.5:1 compression with a 266
camshaft and LCB header; stock cylinder head, stock pistons, single 1
3/4" SU carb, stock everything else. The 1275cc Race unit had 12:1
compression, Longman GT17 head, High lift rockers, 296 scatter pattern
camshaft, Omega piston, twin 1 3/4" Su carbs, etc., etc. The 1380
blown motor has a mechanical compression of 8.5:1, a stock cylinder head,
"AE" big bore pistons, "731" style camshaft and a 5-speed
transmission. Boost is 4 to 6 PSI. The only change for the race 1380 was a
boost increase to 10 to 14 PSI. The horsepower numbers are tremendous but
the "feel" of power, the torque, the grunt is even more
spectacular.
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