Motor

Sportmatic Rediscover│Restore Royal Purple 2.4 Carrera 911S

This articleNo one can ignore it! Rare Porsche 911S wearing beautiful purple]Is continued.

The engine was completely disassembled and all consumable parts were replaced with new ones. At the same time, the pistons and cylinders were replaced with new ones made by Mare and rebuilt. Phil gave the details. "Porsche has developed a stronger magnesium crankcase. The landmark is that the cast number ends with" 7R ". Initially, this case was reserved exclusively for the RS version, but in 1973 As the year of production progressed, it was expanded to other models. ''

"This car was manufactured in the late 1973 and uses a 7R case. The 2.4 7R case is widely accepted as the strongest of the magnesium cases. It has a small cylinder bore opening At 2.7 liters, on the other hand, we need to cut each cylinder and widen the bore by 5mm, which reduces the structural strength. "

"Mechanical injection fuel pumps end with the numbers 013 or 021, which are also exclusive parts for the 911S. The material of the pump body was changed to aluminum in the middle of 1973. Before that, it was made of magnesium. 2.7 RS In the model, the pump body is all aluminum, and this is the suffix number 019. ''

Let's talk about transmission. Today, many people are unfamiliar with Sportmatic and how it works. A similar idea was used in Volkswagen in the early 1960s. It is a three-stage gearbox called Saxomat, which is simply a combination of a manual gearbox and a centrifugal clutch.

The Porsche Sportmatic was based on a four-stage transaxle, which was virtually identical to a regular 911 four-stage manual gearbox. Sportmatic transmissions are available in Type 905 [early version based on 901 gearbox] and 925 [based on 915 gearbox].

The concept itself is similar to the Saxomat, but the Sportmatic uses a torque converter consisting of three elements instead of a centrifugal clutch to transmit the driving force progressively. This is combined with a normal dry clutch, which operates with a vacuum servo whenever the driver changes gears. The torque converter is manufactured by Fichtel & Sachs for Porsche, and the function of a normal flywheel is performed by the torque converter.

As the name implies, a torque converter amplifies the torque of an engine in a low rotation range. When the rotation drops further, it stalls [effectively locks up]. At that time, the torque ratio of the Fichtel & Sachs unit is 2.15: 1, and the stall speed is 2600 rpm. Thanks to the torque converter, you can start from any gear.

At lower speeds than the stall speed, the torque converter slips and the clutch gradually engages, just as with a full manual gearbox and dry clutch. Therefore, even in an urban area where stops and starts are repeated, it is possible to drive with the same feeling as a full AT without shifting at all [although the performance will of course drop significantly].

To change gears, simply move the shift lever and select the desired gear ratio. Phil says: "Driving in the sport is simple. There is one golden rule to remember. Once in the gear you want, let go of the lever. The microswitch inside the lever, which works with electromagnetic and vacuum pressure The solenoid valve starts, which activates the clutch, so vacuum, or vacuum, is taken from a port in the throttle body and a reservoir for it is bolted above the engine and below the parcel shelf. Interestingly, Sportmatic doesn't make any noticeable noise when switched on or activated. ''

925/01 is a gearbox exclusively for 911S. Porsche probably combined it with the perfect gear ratio to take full advantage of the engine's performance characteristics.

How do I change gears?・ ・ Continue to next time


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