Boosted Fortune?

Or desecration of an icon?

WORDS JOHN CAREY

Soaring revs and atmospheric induction were once considered core 911 attributes.

So with the base Carrera and Carrera S now twin turbocharged, has Porsche’s icon lost some of its intrinsic character? (Hint: no.)

It's where the engine is, not what the engine is, that makes the 911 what it is. So while 2016’s Carrera and Carrera S will have a boosted boxer six, the mostly new 3.0-litre twin-turbo engine doesn’t alter the fundamentals of the driving experience one little bit.

That’s because, as ever, the engine is aft of the rear axle. The consequently butt-biased weight distribution accounts for the 911’s unmistakable dynamic flavour; the twerky way it rides a road’s heaves and dips, and its clenching rear-end grip accelerating out of slow corners, for example.

If anything, the 2016 Carrera and Carrera S models are even more 911-ish than the current naturally aspirated 3.4- and 3.8-litre models they will replace in March.

Though capacity is reduced, the twin turbochargers of the new 3.0-litre make it a slightly heavier engine overall.

There’s an extra 17kg back there, where only Porsche would dare put it.

It could have been more. According to director of boxer engine development Thomas Wasserbach, the engineering rule of thumb when turbocharging an engine is that it adds around 30kg. Porsche shaved weight where it could to cut this almost in half (see sidebar). The overall weight of the new Carrera and Carrera S is up only 20kg compared to the cars they replace.

The horizontally opposed layout of the 911’s six demands a short piston stroke, explains Wasserbach.

Otherwise it would become too wide to fit. The 3.0-litre twin-turbo has a new crankshaft with a 76.4mm stroke, 1.1mm shorter than in the existing atmo engines. The 3.0-litre’s 91.0mm bore is 6.0mm less than the 3.4-litre and 11.0mm less than the 3.8-litre.

Wasserbach says the bore and stroke dimensions for the 3.0-litre were chosen only after serious study. “We found out this is the optimum to get stability in combustion,” he says of the chamber’s dimensions.

While the 3.0-litre’s crankcase is an evolution of the closed-deck design used in Porsche’s current atmo engines, its cylinder heads are completely new. The key change is a relocation of the fuel injectors close to the centre of the cylinder bore, very near the spark plugs. Making space for both the injection and ignition hardware meant widening the angle between inlet and exhaust valves.

The compression ratio of the 3.0-litre is 10.0:1, which is high for a turbocharged engine. Porsche chose this combination of capacity and compression to provide more immediate throttle response than a smaller engine with larger turbochargers could ever deliver. Similar thinking is seen in the recent twin-turbo V8s of AMG and Ferrari.

Easy-to-access thrust never made any car worse, and the 911 is no exception

There’s an extra 17kg back there, where only Porsche would dare put it

Like those engines, Porsche’s new twin-turbo six is a revver. The 3.0-litre spins to 7500rpm, only 300rpm less than the atmo engines it supersedes.

A small difference in the diameter of the turbo compressors accounts for the power and torque differences between the Carrera and Carrera S versions of the new engine. The former punches out 272kW and 450Nm, the latter 309kW and 500Nm.

In each case, peak power is 15kW more than the current atmo engines.

But the turbo-fattened torque curves of both of the new models means the power difference is even greater at low and middling engine revs. Porsche takes advantage of this with the calibration of the PDK double-clutch seven-speed gearbox. Earlier upshifts further magnify the inbuilt efficiency advantage of the smaller turbo engine.

Naturally, the new engines achieve lower consumption in the test cycle, but they also deliver better efficiency on the road. According to Wasserbach,

Porsche’s real-world testing indicates consumption 0.5 to 1.0L/100km lower than the current non-turbo engines in typical driving conditions.

Also lower is the time taken to reach 100km/h. The new S coupe is the first 911 Carrera to break the foursecond barrier, Porsche boasts. Equipped with optional PDK and Sport Chrono Package (which brings launch control), it will run 0-100km/h in 3.9sec. Porsche’s performance claims, by the way, are probably the most reliable in the business.

So, in pretty much every measurable way the 911’s new engine is an improvement. But do the metrics mislead? Is the twin-turbo 3.0-litre actually a less engaging, less satisfying experience than today’s atmo engines?

Not at all. But the new engine does subtly alter the 911’s character.

Most of our time at the international launch was spent in a Carrera S with PDK, the most popular 911 choice in Australia. The 309kW engine has a lot of low-rev muscle. Easy-to-access thrust never made any car worse, and the 911 is no exception.

The flexibility comes at practically no cost to the twangy top end expected from a Carrera S. You really don’t miss the extra 300rpm of the atmo engines.

What’s different is that the twin-turbo 3.0-litre is a more able engine when taking it easy; it’s happy, and deceptively fast, even when driven lazily.

The sound? Our Carrera S with a double twin-pipe exhaust system (the standard Carrera has a pair of single oval pipes) is quietly civilised at low to middling engine speeds. But the trademark Porsche 911 soundtrack is there at the top. The turbochargers may have made the accent a little more cultured, but it remains fiercely flat-six.

Less satisfying was the Carrera S Cabriolet with optional sports exhaust (central pipes are the visual giveaway) also tried. Top-down and with the switchable exhaust flaps open, the new engine was hoarse, verging on coarse, at low revs. It actually

sounds better with the exhaust flaps shut. The whine of the turbos is clearly audible in the roofless 911, as are the entertaining crackles and pops the sports exhaust emits when going hard.

The twin-turbo 3.0-litre brings perhaps even more change to the appearance of the 911 than the way it drives. Supplying the pair of intercoolers buried inside the rear guards dictated a complete redesign of the car’s rump. Most obvious of the changes is a bold new air intake grille. Behind this is an active spoiler, which also guides ambient-temp air over the air-to-air intercoolers. Once passing through the intercoolers, air exits through ducts sited in a low-pressure area in the bumper, just aft of the rear wheels.

These are exactly where Porsche’s aerodynamicists insisted they be sited, says exterior design chief air Matthias Kulla. He says 12 different proposals for the new rear treatment were studied before one of the simplest was chosen for production. The front of the new Carrera also features 918 Spyder-like active cooling flaps (see sidebar).

There are changes for the 2016 Carrera and Carrera S unrelated to the new engine, too.

Porsche’s PASM adaptive damping system, with a ride height 10mm lower than before, becomes standard. There’s a lovely new standard sports steering wheel and an all-new infotainment system.

The car also gains some tech familiar from much less expensive Volkswagen Group cars, notably automatic post-collision braking to minimise freeway pile-ups.

These extras go some way towards justifying higher prices. The new 911 Carrera will cost $217,800 and the S will be $252,800. Choosing the Cabriolet versions increases these prices by $21,500. Adding PDK costs $5950, Sport Chrono Package $4790 (with PDK) and sports exhaust $5890.

Prices like these mean the new Carrera and Carrera S will remain as exclusive as ever. But they are also as desirable as ever. The twin-turbo 3.0-litre is a proper Porsche engine that’s right at home in the 911’s legendarily loony layout.

The turbochargers may have made the accent a little more cultured, but it remains fiercely flat-six

1 A LIGHTER TOUCH

New twin-turbo 3.0-litre’s weightsaving measures include a crankcase with plasma-sprayed steel cylinder liners, new crankshaft and exhaust system, and a plastic oil pan. weightrankcase ylinder n.

2 BOOST BROTHERS

All-new cylinder heads are fed by turbos from Borg Warner. The 309kW Carrera S gets 2mm-larger diameter turbo compressors, but otherwise it’s identical to the 272kW engine.

3 BLADE RUNNERS

Airflow through new 911’s front-mounted engine radiators is controlled by active louvres. The three blades are adjusted in unison by an actuator.

They’re opened at standstill, but close above 15km/h to cut drag and lift, and stay closed up to 160km/h if no extra cooling is needed.

4 SHORT SHARP SHOT

When fitted with the optional Sports Chrono package, new Carrera and Carrera S now offer five different driving modes: Normal, Sport, Sport Plus, Individual and Sport Response – the latter a ‘push-to-pass’ style function that gives 20 seconds of max attack from the drivetrain.

Model Porsche 911 Carrera S Engine 2981cc flat 6, dohc, 24v, twin-turbo Max power 309kW @ 6500rpm Max torque 500Nm @ 1700-5000rpm Transmission 7-speed dual-clutch L/W/H 4499/1808/1296mm Wheelbase 2450mm Weight 1535kg 0-100km/h 3.9sec* (claimed) Economy 7.7L/100km Price $252,800 On sale March 2016 * PDK with launch control