Text: Jude Morte / Photos: Jude Morte, Brent Co | posted October 09, 2008 00:00
Perfection just got better
The folks over at Zuffehausen (Porsche's headquarters) have acknowledged that, but aren't the type that are satisfied with perfection, and have found ways to improve on it.
Recently Porsche – through its official Philippine distributor PGA Cars – showed that even the best sportscar line on the planet can be further upgraded with the local release of the 2009 911 Carrera model line. The current 911 Carreras now sport Porsche's proprietary PDK (Porsche DoppelKupplung or Porsche double/dual clutch), as a replacement for the Tiptronic S a/t found on the aforementioned Carrera line.
A seven-speed (plus reverse) a/t, the PDK setup finds the odd numbered gears (1, 3, 5, 7 and reverse) on one side and the even numbered gears on the other, operated by two separate clutches placed inboard from the other and away from the gears proper. In theory, PDK is made up of a conventional manual 'box and a hydraulic control system split up into two separate transmission units, all engineered to wedge itself within the cramped confines of a 997 (current 911 chassis code number) 911. Two radially-arranged, hydraulically-controlled wet clutches (meaning the clutch disks are immersed in cooling lubricating fluid, which also keeps the surfaces clean, gives smoother performance and longer life as opposed to dry clutches) use oil to cool and lubricate the tranny, with two separate oil chambers that distribute oil to all parts of the tranny constantly and quickly, even at high lateral movement. For example, engaging Porsche's launch control feature (which allows a tire-screeching but quick off-the-line acceleration) makes the tranny oil flow through the mechanical components at a staggering 42 liters per minute rate.
In reality, the clutch on one PDK transmission opens or disengages while the other clutch closes or engages. Gears are pre-selected based on what the ECU thinks is the most probable (and arguably the most suitable) occasion, and is often in sync with the driver's shifting movement, with little pause in power delivery. For example, when starting off from a standstill, first gear is engaged while second is already preselected, ready to be almost instantly engaged by the second clutch. Once second gear is selected third gear is then preselected ready for another gearchange in just a few hundredths of a second. This is similar to the seamless shift transmissions found in a number of present-day Formula One cars due to the lack of power interruption between gear movement, a big help when accelerating off the line or out of turns.
Porsche's PDK is more efficient than a regular automatic because it's effectively a manual gearbox with two computer controlled clutches. Unlike a regular automatic or the Tiptronic system that PDK replaces, PDK has no torque converter. The lack of a torque converter makes the car move quicker due to the power-robbing ability of the aforementioned piece, and the numbers crunch on the PDK Carrera doesn't lie, according to Porsche. Straight line acceleration through the benchmark 0-100km/h test is increased by as much as 19 per cent, 0.4 seconds quicker to 100km/h than 911s with a manual gearbox and exactly the same engine output. Compared with the original 997-generation 911, the second-generation 997 is around 0.1 seconds quicker to 100km/h due to the more powerful engines. Also, 911s fitted with the new PDK transmission are up to a full second quicker to 100km/h than the Tiptronic equipped models they now replace.
Aside from the PDK, tossed into the 2009 911 Carrera line are a new dynamic gearshift program that turns on instantly whenever you mash the right pedal, and Porsche's own take on direct fuel injection or DFI (billed as Porsche DFI). The former is willing to play with the driver during certain inputs, such as a willingness to downshift properly (read: matching the engine speed with wheel speed) when you enter too fast into a turn. This feature (the dynamic gearshift program) is crucial for those who own rear-wheel-drive Carreras instead of the all-wheel-drive variants, as the downshifting experience can be harrowing (and potentially dangerous) should the car's rear wheels break traction due to improper downshifting. On the other hand, Porsche DFI – found in the "boxer (so called due to the horizontally opposed position of the engines' pistons)" engines of the 3.6L Carrera and 3.8L Carrera S – uses multiple injection for smoother combustion, with a high pressure stratified start-up engine mapping to reduce emissions and better fuel economy (aside from improving performance).
There's also the Sport Chrono Package Plus Kit, an option found only on the 997-body 911 Turbo but is also available (albeit as an option) for the new 911 PDK models. The Sport Chrono pack brings a chronograph lap timer as well as added software for the gearbox that allows even faster, more aggressive gear changes and the aforementioned Formula One-style launch control function that makes for faster take-offs.
And then there are the improvements to the engine's mechanical parts. Both boxer engines now weight six kilos less than their predecessors. A two piece crankshaft replaces the previous four piece system, reducing overall weight and components used. A new electronically controlled oil pump delivers a constant flow of oil to the engine, even under high lateral loads, thus preventing starvation or even overabundance during cornering.
In the sportscar segment (or any auto segment for that matter), to just become the pinnacle of sales, design and engineering achievement is to be left behind. Even with the attainment of (supposed) nirvana, Porsche and PGA Cars still feel that perfection can be increased, and the new 911 PDK is the most concrete example of that action.