SEMI-AUTO UNDER FIRE

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By Stuart Grant

Porsche’s modern PDK gearbox is widely regarded as the leader of the transmission pack, offering the everyday practicality of an automatic setup and also the thrill of manual operation that so many of us ‘drivers’ yearn for. But it is not the first time the firm has attempted to keep fans of both driving modes happy; there was a go in the 1990s with its Tiptronic and even earlier with the fabulously badged Porsche 911 Sportomatic in 1967.

While all three of these strove to combine manual and automatic driving attributes, they skinned the cat in different ways. It all gets rather technical but here are the basics.

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PDK is an acronym for ‘Porsche Doppelkupplungsgetriebe’, which translates to Porsche double-clutch transmission. In simple terms it is two gearboxes in a single case that incorporates two concentric shafts, one for even gears and the other for odd gears, each driven by its own clutch. The key benefit being that it starts to engage the next gear as soon as the clutch on the previous gear’s shaft starts to disengage, which means a super-quick change and uninterrupted power delivery. It first appeared in a testing capacity as a 5-speed in the 956 race car in 1983 and won its first race in 1986 when fitted to a 962.

With a traditional foot clutch pedal to get the 956 and 962s off the line, and the inability to downshift more than one cog at a time, these early PDK vehicles were as labour-intensive to drive as a regular manual. Continued testing came to fruition in 2005 though with the fitment and launch of the PDK to the road-going 911, Boxster and Cayman. Similar in function, the main difference between the race car test units and the production models was the lack of clutch pedal – this was tossed in favour of an electronically-controlled valve body that actuated the correct clutch when it was needed.

PDK cars can be driven in a traditional auto manner, or manual if you choose to operate the swaps via steering-mounted paddles, which blips the throttle on downshifts better than even the fastest footwork can heel-and-toe. In simple speak, the PDK gives you automatic control over a manual transmission.

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Tiptronic, on the other hand, offered manual control over an automatic box. At the heart of the matter was a ZF automatic box, but to meet the brand’s sporting intentions Porsche fitted sensors that read throttle position, engine revolutions, road speed and whether or not ABS was activated. These sensors fed information to the 4-speed automatic, which through some serious equations altered the gear-shift mapping to suit the current driver’s attitude. Five different maps were on hand but if the need for a more manual approach arose, there was an override setup that allowed the pilot to choose his own gearing by using the + or – function on the lever. Oddly, this action was the complete opposite to that of the firm’s race cars, with upshifts requiring a forward stab and downshifts a pull. Later, Tiptronic cars saw the + and – added as push buttons on the steering wheel, which somewhat remedied the confusion, but Porsche never did get to complete the must-have throttle blip so many boy-racers desired.

That said, Tiptronic was seen as a vast improvement over the Sportomatic – which also didn’t blip and give off that iconic flat-6 exhaust note bark. What does sound cool, though, is the name: SPORTOMATIC. Say it out loud. Doesn’t it perfectly suit the trending American advertising taglines and products that surrounded the space race and moon landing period, perhaps doffing the German hat toward the US in the hope of increasing sales to that automatic-favouring land? It has also been mentioned that Porsche needed to convince the FIA motorsport body that the 911 was not a sporting GT but rather a saloon, and eligible for the Group 2 Sedan racing class. And the easiest way to fool the masses that a machine is not a sportscar was to make it an auto.

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In line with this, Porsche tagged the Sportomatic as an automatic but it was a full-on manual box and had no auto setting. Yes, the cockpit featured only two pedals (go and stop) but unless you liked left-foot braking, there was no need to operate the car with both feet.

At the core was a slightly modified 4-speed manual box and the driver would select gears on the fly by moving the lever through a standard H-pattern movement, but without depressing a clutch pedal. Instead of using a foot, the latter was accomplished by means of a vacuum-operated single-disc dry clutch.

While the H-pattern was standard, the symbols atop the ball were anything but, reading ‘P’, ‘R’, ‘L’, ‘D’, ‘D3’, and ‘D4’. P for Park. ‘R’ for Reverse. ‘L’ was similar in ratio to a regular first gear in a traditional manual gearbox but wasn’t recommended unless on a steep incline. For general use ‘D’, which was slightly shorter than a standard unit’s second, was ideal for getting going before the ‘D3’ and ‘D4’ could follow as the velocity and revs increased.  But how did this wizardry happen?

As a driver’s hand moved onto the gear lever, the smallest amount of downward pressure activated a micro-switch, which via a solenoid opened a pneumatic valve and resulted in a vacuum cylinder disengaging the clutch, allowing the syncromeshed gears to change before the clutch was re-engaged as the driver let go of the knob.

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To ensure the Porsche didn’t come to a shuddering halt when stopping at an intersection, no engine-to-box shaft was fitted. Instead a torque converter as used on traditional automatics found a place. This had the added benefit of being a torque multiplier, which meant that the laziest of drivers could opt to pull off in any gear without too much effort. 

On paper the Sportomatic is a clever bit of kit, but in reality it was somewhat of a flop for the 911, and the press lambasted it to a certain degree. One does however get the feeling that most of this negative reaction came because it was a Porsche – the ultimate enthusiast’s car – and the idea of an automatic variant did not fit its sporting credentials (nor, for that matter, did the 5% price hike it had over the regular manual 911). Most reviews ended with a line along the lines of ‘no matter how bad the traffic is, and that your left leg muscles will ache from all the clutch action, there is no need for a 911 that is perfect for both enthusiast and non-enthusiast alike.’

So just how bad is it?

Start-up procedure is as with any automatic or manual: with a crank of the key and a stab of the accelerator, the 2.2-litre flat-6 engine bursts into life with the acoustic that can only be Porsche (this being a 1971 911E, but the Sportomatic was applied across the range of 911s until 1980).

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A glance at the gear knob’s odd lettering sends my brain scrambling. I take the advice not to use ‘L’ unless on a slope or in inclement weather, so I put my hand on the lever and pull it down to ‘D’. Handbrake down, and not knowing what to expect, I gently squeeze the throttle. The 911 trundles off the line. As the revs increase I go for ‘D3’ (and wonder to myself why Porsche omitted a ‘D2’), and tap off the accelerator slightly. It works. As I release the knob and continue accelerating, the car keeps pushing on.

The time comes to drive with a bit more enthusiasm, as any 911 encourages. With a heavier right foot I pull off from the line more briskly. It’s here that the torque converter raises its head, it feels like a slipping clutch, with the result that the busy revs and exhaust noise increase rapidly while the speed remains a bit pedestrian compared with dumping the clutch on a traditional manual. This over-revving continues as you move into ‘D3’ and ‘D4’, only settling down once up to a cruising speed. It’s here that the Sportomatic shows its positives, with a stab of the loud pedal resulting in effortless overtaking as the ‘slip’ pulls the revs up to the right spot on the torque curve. There is one thing I should warn you about – though it shouldn’t be a problem if you’re adhering to proper driving principles – and that is not to rest your hand on the gear lever. Doing this, even with the slightest pressure, results in the switch being depressed and the clutch coming into action. It isn’t only your hand that needs to be watched; a wayward knee might induce the same problem while you’re taking in the Porsche’s outstanding handling attributes on a mountain pass – not ideal to suddenly find yourself in neutral while powering away from the apex!

Around town it seems best to leave the old Sportomatic in ‘D4’ and let the torque converter do the job – it does mean that you have to get used to sounding like you are ‘windgatting’ while going nowhere slowly. The only way to fix this and to improve the acceleration time is to ignore the page in the manual about not using ‘L’ – in this mode the pull-off is more instantaneous and the engine revolutions seem to match the forward motion more accurately.

SEMI-AUTOMATIC UNDER FIRE Idiosyncrasies aside, the Sportomatic is a fascinating bit of technology and was the first step in the direction of gear lever-less Porsches. And perhaps to prove to the moaning ‘purists’ that the Sportomatic wasn’t just a decoy, Porsche took it racing prior to the production car launch in ʼ67. The chosen car was a factory 911R and the race – a gruelling 84-hour endurance at the Nürburgring known as the Marathon de la Route. In the hands of Vic Elford, Hans Hermann and Jochen Neerpasch the 911R Sportomatic proved not only reliable but also fast, and took the overall win. Love it or hate it, inventiveness and relative rarity have combined to make the Sportomatic highly collectable and desirable. And for those 1970s naysayers that felt there was no place for a Porsche that crosses both enthusiast and non-enthusiast borders, go take a test drive in a modern PDK-fitted Porsche – it’s mind-blowing.

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