A Flywheel-Equipped Race Car Leaves Us Whirring for More



Spinning at 36,000 revolutions per minute just two feet from my right thigh, a 31-pound flywheel is screaming like a five-horsepower Shop-Vac with the filter removed. The sound pierces the composite shell of my racing helmet and drills through my form-fitted foam earplugs before painfully slamming into my eardrums.

Yet despite the aching annoyance, I welcome and embrace the high-pitched drone. It means, in the simplest terms, that the monster inside this ballistic carbon fiber cocoon is not only awake, but completely energized.

With a stab of the throttle, the kinetic energy in the spinning flywheel is automatically exchanged for electricity – the charged ions power two strong electric motors on the front axle. Instantaneously bestowed with 200 torque-laden horsepower, the sticky Michelin slicks claw at the pavement with a vengeance. I clench the wheel as the carbon-fiber bodied race car lunges forward with more accelerative force than an F-16 fighter jet at takeoff power.

Welcome to the driver's seat of the Porsche 911 GT3 R Hybrid 2.0.

Peer high up on Porsche's performance ladder, above the two-dozen or so street legal 911 models – above even the GT2 – to find the automaker's most competitive cars. Vehicles bred purposely for the track.

The Porsche 997 GT3 R Hybrid 2.0 is one such model. Compared to its predecessor, which debuted last year, the second-generation hybrid is 20 percent lighter and more efficient without any concession to lap times. While sharing the same paint scheme, the new vehicle is easily identified by its lack of intakes in front of each rear wheel – changes to engine cooling allowed the slats to be dropped and aerodynamic efficiency improved.

Porsche 911 GT3 R Hybrid 2.0 side viewPorsche 911 GT3 R Hybrid 2.0 front viewPorsche 911 GT3 R Hybrid 2.0 rear view

Beneath the orange, white, silver and black wrap, the GT3 R Hybrid 2.0 features a monocoque body of hot-galvanized steel with a welded roll cage. Body panels are carbon fiber and there are lightweight polycarbonate windows on all sides, including the front windshield. At each corner is a height-adjustable suspension with dual coil springs and Sachs gas-pressure fixed-position dampers. The steering rack is power-assisted, with an electro-hydraulic pressure feed, and there is a car-mounted air-jack system for use in the pits.

With help from Bosch MS 4.0 engine management and a race exhaust system, the gas engine is tuned to develop 470 horsepower.

At the front are six-piston monobloc aluminum calipers over 15-inch ventilated iron rotors. The rear features four-piston monobloc aluminum calipers over 14-inch ventilated iron rotors and there are optimized brake ducts aimed at all four to ensure sufficient cooling. Compared to the standard GT3 Cup (which we drove earlier this year), the wheel/tire package on the GT3 R Hybrid is wider to accommodate the extra workload of the tires. The front and rear wheels are one-piece BBS forged aluminum alloy (11.5x18 and 13x18, respectively) with a single central-locking nut, while dry compound Michelin Porsche Cup N1 slicks tires come standard (30/65-18 front and 31/71-18 rear).

Hung behind the rear wheels of the 997 GT3 R Hybrid is a very traditional race-bred gasoline-consuming flat six-cylinder engine. Displacing 4.0-liters, the naturally aspirated four-valve powerplant features multi-point fuel injection and dry sump lubrication. With help from Bosch MS 4.0 engine management and a race exhaust system, the gas engine is tuned to develop 470 horsepower. The standard transmission is a six-speed sequential dog-type gearbox. There is an aluminum clutch pedal on the floor (controlling the triple-plate carbon clutch), but no transmission lever to the right of the driver. Instead, shifting is accomplished via small aluminum paddles on the backside of the steering wheel. A mechanically-locking rear axle differential completes the rear-mounted driveline.

Porsche 911 GT3 R Hybrid 2.0 rear suspensionPorsche 911 GT3 R Hybrid 2.0 brake caliperPorsche 911 GT3 R Hybrid 2.0 wheel hubPorsche 911 GT3 R Hybrid 2.0 engine

Things become very interesting at this point – the GT3 R Hybrid has a completely independent second driveline in the front of the chassis.

Located just to the right of the driver, where a passenger seat would normally be situated, is a large charcoal gray carbon fiber case. At first glance it appears to be a fuel cell, yet the ominous bright yellow "high voltage" warning sticker and large air ducts feeding cool atmospheric air tell a different story. Porsche engineers reveal that a 31-pound composite flywheel, mounted horizontally on oil-cooled ceramic bearings, is buried deep inside. It is called a flywheel accumulator.

The GT3 R Hybrid has a completely independent second driveline in the front of the chassis.

A flywheel is a rotating mechanical device used to store energy. Unlike nearly every hybrid gasoline-electric vehicle on the market today, which require batteries or capacitors to store electricity, the GT3 R Hybrid uses a spinning flywheel mounted on an electric motor/generator. It's a brilliant solution, as a vacuum-encased flywheel unit is not only lighter than a battery pack but is capable of being fully "charged" (accelerated to its maximum speed) and "discharged" (decelerated to a near stop) multiple times a minute without adverse affects – batteries and capacitors would quickly overheat rendering them nearly useless after a short period of such abuse.

Mounted directly to the steel chassis, the flywheel is generally spinning between 28,000 to 36,000 rpm (it is rated to 40,000 rpm). When the hybrid system is activated, the flywheel is charged automatically under braking by two permanently excited synchronous motors that reverse their function to send electrical current to the flywheel motor (the driver may also charge/discharge the system via a steering wheel-mounted button while coasting or even under acceleration). In layman's terms, normally wasted heat (energy) in braking is converted to electricity and sent back to the pavement when accelerating out of a corner or overtaking another race car via twin 75 kW (101 horsepower) motors located on the front driveshaft.

Porsche 911 GT3 R Hybrid 2.0 flywheelPorsche 911 GT3 R Hybrid 2.0 interior

As mentioned, the hybrid drivetrain in the front of the chassis is completely independent of the combustion drivetrain mounted in the rear. This means the GT3 R Hybrid is capable of racing exclusively in rear-wheel drive mode with the hybrid system shut down. Of course, it may also resort to electrical front-wheel drive to limp back to the pits in an emergency. Versatility is an understatement.

The all-wheel-drive Porsche GT3 R Hybrid 2.0 will accelerate to 60 mph in about 2.5 seconds.

With a curb weight of just 2,866 pounds and a total system power of 672 horsepower, the all-wheel-drive Porsche GT3 R Hybrid 2.0 will accelerate to 60 mph in about 2.5 seconds. Its top speed is gearing limited to about 175 mph.

Showcasing Porsche's technology, the second-generation GT3 R Hybrid has been very busy. In June, it competed impressively (despite a last-minute restriction) during the 24 Hours of Nürburgring. In September, it wowed the crowds while competing in an exhibition class during an American Le Mans Series (ALMS) race at Laguna Seca – it outran the entire GT class as it didn't have to pit as frequently. And in October, it was on display for tens of thousands of fans during Porsche's Rennsport Reunion IV.

Autódromo Fernanda Pires da Silva – the famed Estoril race circuit – is located about a dozen miles west of Lisbon, Portugal. The 2.6-mile road course offers drivers an excellent challenge thanks to its hairpins, elevation changes and long front straight. Although out of the spotlight and frequently forgotten (it was dropped from the Formula One calendar more than a decade ago), the venue remains a world-class facility.

Porsche 911 GT3 R Hybrid 2.0 headlightPorsche 911 GT3 R Hybrid 2.0 rear wingPorsche 911 GT3 R Hybrid 2.0 badgePorsche 911 GT3 R Hybrid 2.0 exhaust tips

Today, the track serves a very noble purpose – a fully-fueled race-ready Porsche 997 GT3 R Hybrid 2.0 is in the hot pits, and Autoblog enjoys a rare opportunity to spend some time behind the wheel.

Arriving at the circuit a couple hours early, the first order of business is a track orientation lap with Jörg Bergmeister in a bone-stock 997 911 C4S. The track is wet from an overnight rain, but the former Grand-American Rolex Series Champion doesn't seem to notice. Despite being completely disheartened and now more nervous than ever, I shake it off and head over to the Porsche trailer to suit up. Ten minutes later I emerge wearing all of my fireproof gear and carrying my helmet and HANS Device (upgraded with a sliding tether system) under my arm. I grab a sugar-free Red Bull and march over to the hot pits.

I check in just as the GT3 R Hybrid enters the far side of pit lane. Despite being a full two hundred yards away, it is unmistakable with its distinctive white and orange bodywork. Sitting fat and low on the tarmac, its yellow headlights glare piercingly at me as it cackles through each downshift. It is damn intimidating.

The ignition is killed and the two beady eyes are extinguished, breaking its stare. The Porsche quietly rolls to a stop in front of me.

Porsche 911 GT3 R Hybrid 2.0Porsche 911 GT3 R Hybrid 2.0Porsche 911 GT3 R Hybrid 2.0Porsche 911 GT3 R Hybrid 2.0 tires

Climbing into a race car with a full cage and not looking like a complete tool requires some planning. As I am six-foot two-inches tall, I put my helmet and HANS on first (most cockpits don't have enough room to lift it cleanly over my head). This means tiny foam earbuds, each with miniature speakers, go into my ears and a Nomex balaclava is slid over my head before my helmet. With the steering wheel removed, I swing both legs over the side intrusion beam, grab the top of the cage with both hands and gently drop myself into the racing bucket. The carbon fiber seat is thinly padded with fire-resistant upholstery, but the thickness of my Nomex suit adds a bit more cushioning. It is tight, but comfortable. With my arms raised, two crew members reach across the cabin and strap all six buckles into the quick release latch just below my beltline. I cinch each as tight as I can while one of the crew attaches the communication electronics jack. I'm ready to roll.

The $6,000 interface appears more sophisticated than the instrument panel on an Apollo command module.

Pre-flight instruction is short, but critical. Nearly all of the primary instrumentation and controls, with the exception of the brake, accelerator and clutch, are located on a flat carbon-fiber panel of the thick suede-wrapped steering wheel. As a result, the $6,000 interface appears more sophisticated than the instrument panel on an Apollo command module. Truth is, there are only a few buttons/switches that require attention as most of the R Hybrid is automated – nearly everything on the face of the wheel is for driver override. Most critical today is the small "Hybrid Map" wheel, at about 7 o'clock in relation to the Porsche crest in the center of the hub. The twelve adjustable-on-the-fly settings change hybrid boost from full auto to system discharge.

Some factory drivers prefer manual control of boost and energy recuperation, so there are buttons for that ("Boost" and "Rekup") and buttons to alter system torque vectoring ("TV IN" and "TV OUT"). Of course, the traction control ("TC MAP") and engine ("ENGINE MAP") are also cockpit-adjustable. Lastly are two rows of bright LEDs. The top row displays engine revolutions, while the bottom shows the flywheel's state of charge ("SOC"). Confused? Yeah, me too.

Porsche 911 GT3 R Hybrid 2.0 steering wheel

After a brief radio check, a crew member flips the console-mounted main ignition switch ("MAIN SWITCH") and I receive the signal to hold down the engine start button ("STARTER"). The tuned 4.0-liter flat-six takes a sip of fuel and ignites immediately. A rough idle shakes the chassis while the concussions from the anxious exhaust bounce of the pit walls.

I'm the only car on the circuit, and all eyes are on me.

With the clutch to the floor, I pull back on the right paddle to engage first gear. The big LCD on the steering wheel confirms my choice. Despite gingerly lifting my left leg and feathering a bit of throttle with my right, the engine stalls – a common occurrence (thankfully, the clutch is only used to break inertia). Without skipping a beat I again stab the start button, apply more throttle and cleanly roll out of the pits towards the wide-open track. I'm the only car on the circuit, and all eyes are on me.

The hybrid system is shut completely off (via the "HYBRID" master switch) during the first couple laps so I am able to orient myself with the chassis and handling without distraction. Despite the electronic castration, the Porsche is still sending 470 horsepower to the rear wheels. I drive guarded, at maybe five-tenths, to get a feel for the brakes, turn-in and available grip. There is plenty of power and the track is still damp. All it takes is a slight goose of the accelerator and the coupe squiggles on the asphalt as the cold rear tires lose grip. Braking is a bit unnerving as the pedal travels a bit then stops – one has to press the seemingly frozen pedal impossibly hard. After a couple minutes, the radio call comes to bring me back into the pits.

Porsche 911 GT3 R Hybrid 2.0

Stopped a minute later with the engine shut down, the driver's door opens and the very patient man at the other end of the radio is waiting. He is Owen Hayes, Porsche's GT3 R Hybrid chief engineer and my personal Obi-Wan Kenobi for the test drive. Owen leans in and flips "ON" the master switch for the hybrid system, moves the hybrid map to "10" and then gives me the signal to head back out.

I had been warned that the hybrid system would make the GT3 R feel sluggish during its initial charge, but I had underestimated the effect. After half a lap, following several regenerative braking cycles, the heavy front wheels magically lighten. At about the same moment a strange sound begins to emerge from the right side of the cabin – the flywheel had finally come alive. The noise starts as a smooth electric whir, but it soon becomes a deafening howl accompanied by a high-frequency vibration.

The game is completely changed.

There is no need to look at the bank of LEDs, now fully illuminated, to verify the flywheel's charge as the noise tells me all I need to know. Passing the apex of the next corner I mash the throttle and hold on. Thanks to a very sophisticated torque vectoring system, power is sent precisely to the wheel that needs to maintain optimal cornering around the radius. With more than 200 horsepower now being pushed through the front wheels, I expect massive torque steer. Nothing of the sort rears its ugly head, and the steering balance remains just as smooth and precise as before. Dynamically, and as expected, the grip up front reduces oversteer and the Porsche magically pulls itself out of the corner as if tethered behind a Nautique ski boat.

Porsche 911 GT3 R Hybrid 2.0 driving

Boost is short lived, no more than eight seconds with a full charge, but it's plenty of time to exit most corners with energy still remaining in the flywheel. Foot to the floorboards, the GT3 R Hybrid launches itself out of the hole quicker than any street car. The power pins my body against the back of the seat with insane levels of thrust (at one point, telemetry reveals that the GT3 R Hybrid is accelerating in third gear through 77 mph with an unbelievable .8 g's of acceleration). The power is stupefying, and I readily admit that I have never driven anything this quick, on or off a track.

The hybrid's flywheel boost provides an instant 40 percent increase in vehicle power for those fleeting seconds. The acceleration pattern almost reminds me of my high school days when we'd plumb nitrous oxide (NO2) into our engines for a quick hit - but there is no high pressure tank to run dry this time. Aggressively apply the brakes and the system recharges automatically.

The ground still shows large patches of moisture on the track. Yet the warm Michelin race tires brush off the laws of physics and stick to the pavement as if they are covered in hot glue. This is good, as it quickly builds my trust in the vehicle. Within minutes my braking is exceeding 1.2 g and my cornering forces approach 1.5 g. I am pushing hard, but still off the pace of the seasoned pros. The GT3 R Hybrid is laughing at me, asking for more.


My body is being slammed back and forth between the carbon-fiber seat and nylon restraints violently, but everything is happening so fast that it's of little concern. Holding my hands on the wheel, my fingers flick up and down through the gears. Overwhelmed, I focus only on shifting, braking, steering... and breathing.

I can hear the 31-pound flywheel, locked inside its prison chamber to my right, screaming under deceleration and then relieving itself as I accelerate. The pattern is rhythmic, and its wail blocks out the soothing roar of the flat-six and the mechanical whine of the straight cut gears. It is terrifyingly noisy.

Overwhelmed, I focus only on shifting, braking, steering... and breathing.

Two good straights, nearly evenly placed apart on the circuit, give me a chance to relax my grip on the wheel and enjoy a strong blast of fresh air from the vent cut into the exterior mirror. The Porsche will hit about 135 mph on the back section in sixth gear, and I see a consistent 155 mph in the same gear on the front straight if I exit the corners properly (still running the transmission ratios and suspension settings for Laguna Seca, the orange and white race car will need taller gears to go much faster).

A couple laps later, Owen comes on over the communicator and tells me it is time to pit on the next lap. He instructs me to switch to hybrid map "11," which will drain the flywheel while I am on the track (it can also be done in pits, by raising the front end and allowing the wheels to spin off the energy). I crave more time behind the wheel, but part of me is relived as I am both physically and mentally drained. Keep in mind that I've only been in the car for about 20 minutes.

Porsche 911 GT3 R Hybrid 2.0 drivingPorsche 911 GT3 R Hybrid 2.0 drivingPorsche 911 GT3 R Hybrid 2.0 driving

Coming off the last corner, I shift the gearbox into neutral and roll the GT3 R Hybrid the last few hundred feet. As I stop, Owen opens the door and kills the ignition. A member of the pit crew attaches an air line to pneumatically raise the Porsche off the ground while other members of the crew immediately start to remove the wheels. Another plugs a dump can into the dry break valve on the hood and splashes in more Panta racing fuel. I unbuckle and muster the strength to climb out through the labyrinth of roll cage. Once clear, I remove my helmet. Standing in the hot pits and taking in the welcomed silence, I realize that I am not only completely soaked with sweat, but I am completely exhausted.

The GT3 R Hybrid 2.0 is absolutely spectacular, yet Porsche is still chasing perfection.

Minutes later, while gulping down a cold orange juice in the garage (and waiting for my pulse to drop below 165), I find myself almost speechless. The GT3 R Hybrid 2.0 is absolutely spectacular, yet Porsche is still chasing perfection.

Last year's model, the first-generation, relied on the driver to control recoup and boost. However, Porsche found that each of its drivers would use the hybrid system differently and this caused inconsistency in tire wear and fuel economy. The engineers tried a GPS-based boost program (it would "learn" the track and provide boost at the proper moment), but satellite-based positioning doesn't work when passing slower vehicles off the racing line. The solution was the current automated system to deliver boost to the front wheels based on throttle position and other sensors. This works well most of the time, but there are situations when drivers don't need the boost (e.g., exiting a corner behind slow traffic), preferring it to remain stored in the flywheel until passing. Porsche drivers still use the manual overrides in these situations, admit the engineers.

Porsche 911 GT3 R Hybrid 2.0 driving

There is also an interesting phenomenon that occurs during braking. Under initial brake application, the hybrid's regenerative system produces heavy drag as it is diligently electrifying the flywheel motor. However, once the flywheel has absorbed its maximum energy (at about 36,000 rpm) it abruptly shuts off - the drag on the front wheels is eliminated and the vehicle shoots forward under standard braking force. The driver has to anticipate this switchover, or they will find themselves overshooting the entry, or worse go right into the wall.

The Porsche GT3 R Hybrid 2.0 is a clear look at the next-generation of exhilarating personal hybrid transportation.

Peculiarities out of the way, Porsche's hybrid system works very, very well. But as of now, the GT3 R Hybrid 2.0 still hasn't raced for a spot on the podium. Its unique hybrid powertrain leaves it a bit ostracized, without a class in which to compete. Today's game-changing hybrid race car remains nothing but a very fast proof-of-concept. But don't expect that to dissuade Porsche, an automaker obsessed with winning. Revealed earlier this year was the 918 RSR Hybrid - also fitted with a flywheel accumulator – expected to mark the brand's return to the famed 24 Hours of Le Mans in 2014.

Thankfully, crash helmets and Nomex suits won't always be required to pilot a vehicle equipped with a flywheel accumulator. The technology not only promises a clean, safe, lightweight, environmentally friendly and completely self-contained alternative to battery storage, but it delivers fun-to-drive free boost. I am convinced that the Porsche GT3 R Hybrid 2.0 isn't just a glimpse at the future of racing – it's a clear look at the next-generation of exhilarating personal hybrid transportation. Maybe it's time for the Prius, and its numb clones, to finally move aside.