Article by: Daree Lee
Audi has demonstrated the
effectiveness of a supercharger driven by an electric motor. The electric
compressor (highlighted in red in the picture) is incorporated into the
turbocharger plumbing to build up pressure immediately at low speeds,
particularly during the lag period between idle speed and full turbo boost.
The unit looks like half a
turbocharger, since there is no exhaust-driven turbine coupled to it, instead
having an electric motor coupled directly to the compressor shaft. It spins to
maximum speed the instant it is switched on by the ECU (engine control unit).
Incorporated for testing
purposes into a 308bhp single-turbo 3-litre diesel A6, the electric blower
makes a significant difference in the
car’s off-boost behaviour. The compressor totally wipes out initial lag, giving
the vehicle a significant advantage in the first few seconds of
acceleration from a standstill.
Using an electric
compressor to “close” the lag-zone in a turbocharged engine makes plenty of
sense and works remarkably well, as we found out after driving the Audi
prototype. The installation requires few additional components and the assembly
is elegant in its simplicity.
With the current generation
of motors, the electric compressor could function on its own as a
cost-effective, low-pressure supercharger to raise the internal-combustion
engine’s overall torque.
There is just one small
problem, though - existing 12-volt electricals cannot cope with the power
demanded by the compressor motor.
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