EFFECT OF NEGATIVE SUPERCHARGING ON INTERNAL COMBUSTION
ENGINE

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ABSTRACT
Until recently, Automobile manufacturers uses supercharger & turbocharger to supply
air-fuel mixture at a pressure above atmospheric. Up to 40% increase in power & torque may be
obtained by supercharging. As a typical example , in the Chrysler 2.2L turbocharged engine, the
turbocharged provides 35% more torque & 50% more power compared to the same engine
without turbocharger. To achieve above purpose, air pump, computer & also intercooler (in
between the supercharger & the engine) to be used. Intercooler is required as: In petrol engines,
if the charge density is increased & if same octane number petrol is used, then to avoid
detonation, compression ratio must be decreased. A lower compression ratio will results in
decreased air standard & hence lower thermal efficiency and as in the turbocharged engines, due
to higher peak cylinder pressure, are more prone to detonation, the compression ratios have to be
reduced, which reduces air standard efficiency.


Introduction to Negative Pressure Supercharging
The Negative Pressure Supercharging concept was first conceived 1983 in Sydney Australia by
Alexander Chabry, a 21 year old self-taught engineer with a remarkable insight into the fluid
dynamics of the conventional 4-stroke engine. He was inspired by the fast acceleration produced
by the low revolving 225 Chrysler slant 6 and the massive towing power (torque) produced by
heavy trucks. He figured cars could use low rpm torque instead of high rpm horsepower to
substantially improve acceleration and fuel economy.



Camshaft with Synchronized Valve Timing, high intake lift and low exhaust
lift
• Traps the lower pressure (higher vacuum) in the cylinder at
the end of the exhaust stroke by closing the exhaust valve
early and using less overlap duration and exhaust valve lift
• Moves the lower pressure (higher vacuum) to the intake
stroke during the overlap period by synchronizing the exhaust
valve closing, overlap duration and exhaust valve lift events
• Traps the larger volume of air pulled into the cylinder during
the intake stroke by closing the intake valve early
• Prevents the lower pressure (higher vacuum) from pulling the
intake charge into the exhaust system during the overlap
period