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PORSCHE 911T Engine Modification: Operation

At speeds above 1350 RPM, during periods of high manifold vacuum with throttle plates closed (engine overrun), RPM switch is activated, causing electro magnetic valve to open allowing the high vacuum in intake manifold to reach diaphragm in by-pass valve and open it. This permits an additional air/fuel mixture to pass into inlet ducts of the individual cylinders, ensuring good combustion and optimum emission control. RPM switch is de-energized below 1300 RPM, shutting off by-pass valve and allowing normal idle speed system to come into operation.

NOTE: Should throttle plate by-pass valve be in operation, a micro switch located on accelerator linkage would shut off by-pass valve when throttle plates are re-opened.
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