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= Porsche Sportomatic = The Porsche Sportomatic transmission was introduced by Zuffenhausen in 1967. It represented a novel approach to gearbox design by blending aspects of manual and automatic transmissions. It was a semi-automatic transmission used in Porsche 911 between 1967 and 1980 and was based on the transmission unit from the 905. A small number of 914s were also fitted with this transmission. This semi-automatic design eliminated the need for a clutch pedal, permitting gear changes through the mere movement of the gear stick. The torque converter facilitated smoother power delivery and prevented engine stalls at slower speeds. The Sportomatic system was designed to broaden user accessibility to Porsche's sports cars by offering a driving experience that combined the control and engagement of manual shifting with the convenience of automatic operation.

Sportomatic Transmission
The Sportomatic was Porsche's hybrid approach to gearboxes, combining elements of both manual and automatic transmissions. Depending on the model, it was available in either 4-speed or 3-speed versions. The gearbox system did not automatically shift gears; instead, drivers had to change gears manually without a conventional clutch pedal. This system used a torque converter, typically found in automatic transmissions, which allowed the car to idle without stalling and eliminated the need for a clutch pedal by engaging the gear shift with a simple push on the gear stick.

Engagement and disengagement of the clutch
The push on the gear stick activated a micro-switch in the lever, triggering a system to automatically disengage the clutch to allow for smoother gear changes. The micro-switch then started a solenoid, which is an electromagnet used to perform mechanical action. When activated, the solenoid opened a valve that controlled the flow of air or gas in a closed system (in this case, pneumatic, meaning air-powered). Opening this valve allowed air to flow into a vacuum cylinder, a component that uses air pressure differences to create movement. The movement in the vacuum cylinder was used to disengage (or separate) the clutch. The clutch is a component that connects or disconnects the engine's power from the transmission. By disengaging the clutch, the car was able to switch gears smoothly without the driver needing to manually operate a clutch pedal. This process enabled smoother gear shifting through the use of synchromesh gears. These gears align and engage more efficiently than older designs, reducing gear grinding. Upon releasing the gear lever, the clutch automatically reengages, seamlessly reconnecting the engine’s power to the transmission.

Torque convertor
The Sportomatic featured a torque converter instead of a traditional flywheel, a feature more common in automatic transmissions. This configuration allowed the vehicle to remain idle without the risk of engine stall or requiring the driver to shift to neutral manually. The use of a torque converter, which replaced the direct mechanical connection between the engine and the gearbox, caused Porsche to incorporate a 'Park' function in the Sportomatic. This feature was designed to secure the vehicle when stationary, as the absence of a mechanical link means the car could potentially roll if not adequately secured. The 'Park' function achieves this by locking the lay shaft, an essential component within the gearbox responsible for transferring power from the engine to the wheels. Locking this shaft prevents the vehicle from moving, ensuring safety and stability when parked.

The gears were labelled L, D, D3, and D4, and there was a notable absence of D2, a gear commonly found in cars with manual transmission. 'L' or 'Low' functioned similarly to the first gear in manual transmissions, but Porsche recommended starting in 'D' for normal driving conditions. 'D' and 'D3' offered gear ratios slightly shorter than the corresponding second and third gears of a manual gearbox, with 'D3' providing a longer ratio suitable for overdrive. To stop the car, the driver just had to apply the brakes without requiring to shift out of gear or manually disengage the driving mechanism.

The torque converter shared the engine's oil system, which allowed it to increase the oil capacity by 2.3 litres. It allowed the 911s equipped with Sportomatic to start in any one of the four gears due to the torque converter acting as a torque multiplier.

Car and Driver Test Results
The 4-speed transmission remained in production until 1979, receiving an upgrade in 1975 to accommodate the increased power of the 2.7 engine. The later models of the Sportomatic were based on the 915 transmission and featured three speeds instead of four.