Porsche 911 Carrera, 2009

Porsche 911 Carrera, 2009

 

The very first sports car to bear the Porsche name was introduced to the world in June, 1948. Therefore, as the proud, independent Swabian automaker celebrates sixty years of sports car excellence, it is only fitting that it has a new Porsche 911 Carrera - for many the quintessential Porsche-to help mark the milestone.
This latest Porsche 911 Carrera Coupe and its higher-performance variant, the 911 Carrera S Coupe, are the most sophisticated, potent and environmentally friendly Porsche 911 Carrera models that Porsche has ever offered.

Despite their abundance of 21st century technologies, the 2009 911 Carrera Coupe and Carrera S Coupe clearly trace their engineering and aesthetic roots to the seminal Porsche. That original car evolved over fifteen years from the highly coveted 356 to the first 911 when, at the 1963 Frankfurt Motor Show, the ground-breaking 1964 911 Coupe debuted. As a testament to the genius of its design, after more than forty years of development and six generations of engineering improvements, the 911 Carreras still showcase a horizontally opposed, rear-mounted six-cylinder engine carried in a distinctive and instantly recognizable body.

Less Fuel In, More Power Out
Though the 2009 Porsche 911 Carrera Coupe and 911 Carrera S Coupe are each propelled by Porsche's familiar horizontally opposed, six-cylinder "boxer" engine, and despite the fact that both engines carry the same displacement designation as their immediate predecessors, both are substantially different than in 2008 model year.

Most critically, both the 3.6-liter engine in the Carrera Coupe and the 3.8-liter in the Carrera S Coupe are now equipped with direct fuel injection. In addition, the engines are of a new, more robust construction than before, boasting a two-part crankcase for increased structural rigidity. Further, both engines benefit from higher compression ratios and improved breathing, compared with the previous versions.

The results are astounding and immediately rewarding to the driver. The 2009 911 Carrera Coupe develops 345 horsepower at 6500 rpm and 288 lb.-ft. of torque at 4400 rpm. That's an output of 95.5 hp per liter and represents an increase of 20 hp and 15 lb.-ft. At the same time, fuel consumption is reduced by 6.4 percent over last year, when the cars are equipped with a manual gearbox. The all-new PDK transmission further improves fuel economy over the previous Tiptronic S, by a total of 12.5 percent.

This new engine propels the Carrera Coupe with a manual gearbox from a standing start to 60 mph (96 km/h) in 4.7 seconds and achieves a top speed of 179 mph (289 kmph) on the test track.

The blazingly quick Porsche double-clutch automatic transmission takes two-tenths of a second off that run, making the 0 to 60 mph (96 km/h) sprint in 4.5 seconds. The top speed is a track-proven 178 mph (287 kmph).

In Porsche Parlance, "S" Means More
The 2009 Porsche 911 Carrera S Coupe, like its predecessor model, is powered by a larger, more potent version of the Porsche horizontally opposed six-cylinder than its non-S sibling. As with the 3.6-liter version in the Porsche 911 Carrera, the 3.8-liter engine benefits from less weight, a two-piece crankcase, improved intake and exhaust, and direct fuel injection. The fruits of these refinements are 385 horsepower at 6500 rpm and 310 lb.-ft. of torque at 4400 rpm. This is an increase of 30 hp and 15 lb.-ft. of torque while achieving a power output of 101.3 hp per liter, without the need for any form of supercharging.

With a boost in potency, the Porsche 911 Carrera S Coupe with manual gearbox runs to 60 mph (96 km/h) in only 4.5 seconds, on its way to a track-proven top speed of 188 mph (302 kmph).

It Starts With a Straight Shot
Both the 3.6-liter and 3.8-liter horizontally opposed, six-cylinder engines in the Porsche 911 Carrera Coupe and 911 Carrera S Coupe are substantially revamped from the similarly designated engines in last year's model range.

The engines still consist of a light alloy crankcase and cylinder heads, and have four valves per cylinder actuated by dual overhead camshafts. Now, for the first time in a Porsche sports car, the engines boast a direct fuel injection system (DFI), which works in concert with Porsche's VarioCam Plus valve lift and timing control.

By injecting fuel directly into the combustion chamber rather than in the intake port, DFI delivers myriad benefits. Since the fuel charge arrives closer to combustion than with port injection, throttle response is instantaneous, and the Porsche 911 Carrera driver feels a razor-like reaction to even the slightest movements of his right foot, whether accelerating or lifting from the throttle.

To take fullest advantage of the DFI's attributes, Porsche's engineers designed the combustion chamber and piston crown to maximize efficiency. Those refinements allowed the engineers to design both the 3.6-liter and 3.8-liter engines with a compression ratio of 12.5:1. This is up from 11.3:1 on the previous 3.6-liter and 11.8:1 of the former 3.8-liter. To ensure maximum efficiency and durability, the DFI injectors have been designed and manufactured to deal with working pressures of up to 1740 psi (120 bar) in the combustion chamber.

The fuel injector nozzle is between the two intake valves, spraying fuel directly into the incoming fresh air charge from both valves. This is clearly far more efficient than port injection which naturally leaves some unburned gasoline on the intake walls and valves. The incoming fuel charge further aids the combustion process by cooling the incoming air as it vaporizes, allowing more air to be drawn into the engine for a denser charge and permitting the higher compression ratios. Finally, the fuel and air are mixed more evenly and thoroughly when the fuel is injected directly into the air inside the combustion chamber.

DFI also reduces emissions since the engineers were able to reshape the piston crown to completely direct the fuel charge at the spark plug for thorough combustion. During start-up, the engine benefits from high-pressure stratification of the injected fuel. Then to quickly light off the catalysts, the DFI heats the exhaust rapidly through multiple injection. To increase the temperature of the exhaust gas to an even higher level, ignition timing is very late, further minimizing start-up emissions.

The system also employs multiple fuel injection during periods of combined high loads and engine speeds up to about 3500 rpm-as when the driver floors the throttle at slower speeds. During the multiple injection phases, the injectors split the fuel charge into several successive bursts during the piston's intake stroke. Otherwise, the fuel is injected in one phase during each intake stroke.

As with their predecessors, the new 3.6-liter and 3.8-liter engines are equipped with Porsche's VarioCam Plus intake valve timing and lift system. Porsche's engineers have refined the elements and operation of the VarioCam Plus to optimize the benefits of the DFI. The engineers re-aligned the profiles of both the intake and the exhaust camshafts. The diameter of the intake tappets has been reduced from 33 to 29.5 mm (1.30 - 1.15 in.) and the exhaust valve tappets are down from 33 to 24.2 mm (1.30 - 0.94 in.). This reduction in mass allowed the engineers to safely raise the engines' redlines, from the previous 7300 rpm to 7500 rpm.

Two, Two Camshafts in One
As with all Porsche engines, VarioCam Plus in the Porsche 911 Carrera and Carrera S Coupes adjusts intake valve lift and timing based on engine speed and load, and is under the umbrella of the engine's main electronic controller. Though the VarioCam Plus operates far too quickly for the driver to be aware of it, the results are obvious. The effect is that of an engine with two different intake camshaft profiles, one set up for smooth and efficient around-town driving, the other a high-performance camshaft designed for high-speed. Each of these two designs usually precludes the other and most cars have a compromise of the two. Porsche's VarioCam Plus removes the compromise and the driver benefits from the best of both driving worlds.

More Efficiency through Better Breathing
The Porsche VarioCam Plus in the new engines has also been refined to take full advantage of their redesigned, freer-flowing intake manifolds. The new intakes boast a dual chamber design, in place of last year's single chamber unit. The intakes have two openings and separate intake funnels in the rear engine cover. These funnels feed air to separate, round air filters. Besides greatly reducing flow resistance, the dual filters provide a side benefit to owners: The replacement interval has been increased from 37,000 to 56,000 miles.

As with the previous model, the upper section of the 3.8-liter engine's filter features actively switchable resonance volume. Additional volume is activated as a function of engine speed, with temperature compensation being provided by a vacuum-controlled butterfly, improving the engine's acoustics.

The new intake manifolds themselves are made of a special synthetic material. They incorporate a resonance pipe integral with the air-distribution pipe between left and right intake runners, as well as additional resonance chambers. The larger engine in the Porsche 911 Carrera S Coupe also has a switchable resonance butterfly, which adjusts the oscillation of the intake charge to maximize torque at lower engine speeds. At full load between 2600 and 5100 rpm, the resonance butterfly is closed; at lower and higher speeds it is open.

The exhaust manifolds are also new. The lengths of the individual exhaust runners have been equalized and optimized for smoothness and efficiency. The catalytic converters are directly behind the right- and left-hand manifolds, rather than being mounted crosswise behind the engine. Thanks to the engines' DFI, there is no need to inject secondary air into the exhaust stream to complete combustion, as in the past.

Stronger, and Lighter, Too
While gaining sophistication, technology and power, the new horizontally opposed, six-cylinder engines in the 2009 Porsche 911 Carrera and Carrera S Coupes lost weight.

Both engines are 13.2 pounds (6 kg) lighter than their predecessors. Among the critical changes to the basic engine design is a new two-piece crankcase instead of the previous four-piece unit. The new crankcase has integral crankshaft bearings, compared with the former separate crankshaft bearing housing. In addition to reducing complexity, Porsche's engineers enhanced the thermal and mechanical stability of the engine. They also went from an open-deck to closed-deck layout. With the closed-deck configuration, the tops of the cylinder liners are now connected with the housing by a top plate which incorporates the coolant sleeves. This design increases stability and durability while helping reduce oil consumption and friction.

Further weight and complexity are saved through the elimination of the intermediate shaft needed to drive the timing chains on the old engines. Thanks to new, highly resistant timing chains, that shaft is not needed. Porsche's engineers also developed new one-piece cylinder heads which incorporate the camshaft bearings and the guide cylinders for the hydraulic cup tappets.

Leaving no stone unturned in their quest for maximum efficiency, Porsche's engine designers developed a new engine lubricating oil system that ensures thorough lubrication regardless of driving conditions while minimizing operating losses for improved fuel economy.

Given the Porsche 911 Carrera Coupe and Carrera S Coupe are designed to be driven quickly and enthusiastically, every element of the cars must withstand extended periods of high levels of lateral acceleration. Drawing from decades of racing success, Porsche's engineers ensured the cars' engines would always be adequately lubricated, even under the most extreme driving conditions. The new engines use Porsche's proven dry sump system, with four intake and one electronically controlled, pressure oil pump operating on demand. The engine's electronic management system adjusts the supply of oil by means of a hydraulically activated, axially moved gear in the pressure pump. As the gear is moved, its mesh section width is changed, varying the volume of oil moved. The pump runs on a chain-driven shaft spun by the crankshaft. The result is optimum lubrication with minimal energy consumption.