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How Porsche’s Dynamic Boost System Works

Most rally fans know the hallmark sound of an anti-lag system. First used in Formula 1 in the 1980s, anti-lag systems are designed to keep a turbocharger spinning while off throttle. Most systems produce a loud « pop, » often accompanied by visible flames. Though some owners of modified cars will tolerate the occasional fireball, a new Turbo S owner might find this trait unappealing. From an environmental perspective introducing additional unburned fuel outside the combustion chamber is also less than ideal. Between the added noise and constantly needing to wipe soot and scorch marks off the rear bumpers, a fuel-driven anti-lag is not well suited to a modern high-end performance car. In order to maintain boost while off-throttle Porsche has come up with a different solution.

Maintaining Boost Without Adding Fuel

Per Engineering Explained, the Porsche system sets itself apart from traditional anti-lag by not requiring additional fuel to maintain boost. No extra fuel, no fireballs. The so-called Dynamic Boost system instead uses the electronic throttle body to maintain airflow through the engine. Normally when the throttle pedal is released the throttle butterfly closes fully. Porsche’s system opens the throttle butterfly partially, maintaining some boost pressure in the intake and facilitating airflow through the engine.

This additional airflow has two primary functions. The first, and most obvious, is to facilitate spinning the turbochargers. This aids in maintaining boost pressure when off throttle. The second is to keep the intake manifold from becoming an area of negative pressure. The latter component aids in throttle response, which is valuable in a heavily turbocharged engine.

The system does have one notable downside; with the Dynamic Boost system the effect of engine braking is dramatically reduced. Remember, the system’s goal is to flow air through the engine, which effectively negates compression braking. The effect is most noticeable with the car in Sport and Sport+ modes, when the car is less likely to rely on compression braking. In situations where the effect is most pronounced the driver will primarily use the brakes to slow the car anyways.

In the interest of disclosure, Porsche is not the only manufacturer to come up with this solution. Ford also holds a patent for a similar system. Several of the traditional anti-lag methods, including the D-Valve method and inlet bypass share some similarities with both the Porsche and Ford systems. These competition-proven do still rely on adding unburned fuel into the system, and lack the necessary sophistication and clean burn required for a street car.


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Rear Wheel Steer vs. Thrust Vectoring: Turbo S Meets F-22 Raptor


Saabs may have been born from jets, but even the mightiest SPG has no place on a runway alongside the F-22 Raptor. The current 911 Turbo S has a spec sheet that reads more like the ultimate air superiority fighter than a mere road car. Dynamic roll control, dynamic boost, and a whole bevy of acronyms that sound more like missile systems than performance enhancing options only add to the illusion. With PCCB, PSM, DRC already on the list of standard features, what’s a JSOW between friends? In this CGI spotlight on the 991 Turbo S, Bipolar visual studio and Zelig sound pair the ultimate turbocharged 911 against the first Fifth Generation fighter jet.

While nothing about the 911 Turbo is designed to reduce radar cross-section (as far as we know), the car does share some attributes with the F-22. The Turbo’s emphases are on enhancing maneuverability, and true multi-role capability, much like the fighter. While the F-22’s roles are substantially more threatening than the Turbo’s, both are capable of a varied mission set. The Turbo is equally happy on track, daily driving and covering great distances at speed. The F-22 on the other hand is much better suited to air superiority, ground attack and signal intelligence roles. Dropping by the local ball park isn’t on its mission list, that job is best left to Marine helicopters.

For those who might be interested in how this video came together, Bipolar kindly released a making of video, showcasing the breadth of their CGI talents.


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930 v 991: Open-top Turbos

Though it is seldom recognised, 1986 was a very important year for Porsche. A full year before ‘Black Monday’ and the ensuing global financial crisis, the 911 was flourishing, buoyed by its resurgence in fortunes under charismatic CEO Peter Schutz. Sales were strong off the back of an ever-increasing expansion to the range: Carreras were available in Coupe, Targa, or even Cabriolet form – the latter, of course, being introduced just three years earlier – all of which could be specified in either a narrow or a widebody ‘Turbo-look’ body style.

However, the significance of 1986 lies not with the naturally aspirated 911 Carrera, but its forced-induction compeer. The 911 Turbo, still very much an automotive icon more than a decade after its first release, was finally allowed back into the United States after Porsche refined the car’s emissions credentials – though the caveat was the US Turbo came equipped with slightly less power than its European brethren. Also in 1986, the Turbo became available as a Cabriolet.

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Boasting a fully electrically-operated hood (which was then also offered as an option on Carrera Cabriolets) the Turbo Cabriolet brought fresh-air motoring to those who had wallets big enough to swallow a purchase of an illustrious turbocharged 911. The open-topped Turbo was a success: nearly 3,000 were sold between 1986 and the final year of 930 production in 1989.

However, the 930 Turbo Cabriolet looked set to be the first and last of its kind – seemingly killed off with its super-rare Targa variant – as both 964 and 993 generations of Turbo remained Coupe only. Of course, the Turbo Targa concept hasn’t rolled out of Zuffenhausen since, but the Turbo Cabriolet did return in 2004, by which time the 911 had switched to water for cooling with the 996.

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Turbo Cabriolets duly followed through both generations of the 997 era (including the Turbo S of 2010) and six months after the 991 Turbo and Turbo S were revealed in 2013, Porsche again unveiled Cabriolet versions.

There’s no denying the Cabriolet has established itself as an important staple of the Turbo lineage and to celebrate that fact, we’ve gathered two high specification drop tops separated by a quarter of a century of Zuffenhausen engineering. The duo of special Turbo Cabriolets in question, a 2014 991 Turbo S and a 1989 930 with full Porsche GB-fitted LE specification (which effectively grants it status as a Turbo S of its time) share a price tag of £150,000.

To read the full feature on our 930 Cabriolet v 991 Turbo Cabriolet head-to-head, pick up Total 911 issue 129 in store now. Alternatively, order your copy online for home delivery or download it straight to your digital device.

See the Porsche 991 Turbo S Cabriolet’s Launch control in action here.


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What we’ve learnt from the Porsche 991: driver experience

This week we’ve been piloting the superb 991 Carrera 2 GTS around Ireland’s simply magnificent Wild Atlantic Way. Aside from taking advantage of some of the very best driving roads in Europe, we’ve done this as part of our in-depth look at the latest generation of Porsche 911, which is due to be replaced in September after four years in showrooms.

Key developments to the 991 are evident in both its performance and chassis over older versions, which we studied earlier in the week, but the truth is there’s a plethora of other revisions to the 991 platform worthy of our comment. So, we’ve picked out the five most notable changes and looked at what effect they’ve made to that all-important driver experience.


1. Sound

There’s no denying the switch to DFI engines produces a different note to the M97 and M96 units before it, but hidden in the 991’s armour is a neat sound symposer, which feeds that glorious flat six resonance directly into the cabin. It’s a small touch but a useful one, as there’s no way the driver won’t feel anything but invigorated by the heightened note of a hard-working flat six behind him. That said, it can make for a noisy cabin at times as the inevitable rolling tyre noise will also receptive to your ears, but that’s always been a trait of later 911s – plus you’re running a sports car with huge 20-inch diameter rubber with a side profile of only 35, so what did you expect?



2. Clocks

These have been much improved ever since the 996 in terms of placement, bringing all five iconic dials within the radius of the steering wheel, neatly doing away with that sloppy smattering of various clocks and gauges right across the driver’s side of the dashboard on air-cooled variants. A further evolution to the 991-generation of 911 has seen the introduction of a digital-only fourth pod. Twenty years ago a full dial was dedicated to telling the time in analogue format, don’t forget, but now the driver is spoilt with a plethora of screens to flick between – and all from the same dial – including, directions, a 3D map, TPM (if optioned), torque distribution (on 4WD 911s), plus detailed vehicle stats including journey time and MPG. Like it or not, it brings out the tech geek in all of us – and the wealth of information constantly available to the driver only aids the Porsche 911’s USP as an intelligent car for the intelligent driver.



3. Seating position

The driver’s throne has evolved substantially in the 911’s 52 years of existence. What was once a fuzzy one-person bench is now an ergonomically refined seat with fully adjustable support for your legs, and lower and upper back. Even better, its positioning is lower than ever, placing your centre of gravity lower in the car. The steering wheel is nice and close, and the gear shifter is similarly well placed just a couple of inches away from that wheel. Much thought has clearly gone into creating a utopian seating position for the keen sports car driver, and the result is emphatic: a seat in a 991 is by far the best seat in the entire Porsche fraternity.



4. Centre Console

It was pretty controversial at first, but four years on we’re warming to the Panamera-style centre console housing the ‘Sport’ and other options buttons. Sure, it puts to bed any lingering thoughts of the 911 being a tight, almost claustrophobic motoring experience, but extra space garnered from the chunky console running between the two front seats actually accentuates a degree of refinement that the 911’s interior has always lacked. In fact, the 991’s cockpit is perhaps the first 911 interior that can truly be described as lavish, and there’s no doubt the Teutonic console aids this, with all requisite buttons now much easier to prod when on the move. Thanks to that console, our days of trying to wrangle our fingers awkwardly around the gear shifter in trying to locate the PASM button are long gone, and we’re very happy about that fact.

Our only gripe? The handbrake is gone, replaced by an air brake with an on/off toggle that’s housed on the dashboard just above your right knee (in a RHD car).



5. Engine

As you can tell, we’re huge fans of the Porsche 991 here at Total 911. However, our outright enthusiasm for the latest-generation of Zuffenhausen’s flagship sportscar deteriorates rapidly when popping the decklid and peering at the bland plastic void staring back at us. Yes, that’s right: with the latest Porsche 911, you’ll have to get on your hands and knees and look under the rear bumper to have any hope of glimpsing the famous flat six engine that powers it.

This move to cover the engine is as bizarre as it is heartbreaking. Officials have told us it’s all to do with sound deadening, but most press cars we pilot come with the optional (and superb) Sports exhaust option, plus there’s the small matter of that internal sound symposer to counter that statement.

Either way, part of the theatre of owning a legendary sports car like the Porsche 911 is being able to ogle at the powerplant that shoots you up the road at the prod of your right foot. Taking that away from the enthusiast remains nonsensical, even after four years of us trying to figure out good reasoning for it. As such, I personally welcome a call from any Zuffenhausen-based Porsche employee who can justify the decision to cover up one of the most beautifully crafted and universally popular engines ever to power a sports car.




So there you have it. The (lack of) engine sight is clearly a sore point, but the 991-generation is an exquisite sports car that’s proved a just and able development in the Porsche 911 story. Its very concept may have took a while for enthusiasts to accept in its entirety, but there’s no arguing against the fact that the 991 is the best generation of 911 yet. We’ll be sad to see its production cease.

What are your thoughts on the 991? Comment below or tweet us @Total911.


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What we’ve learnt from the Porsche 991: chassis

As we told you earlier this week, the 991-generation of 911 has now been in production for four years and, with the facelifted – and turbocharged – second generation due to arrive by the turn of the Frankfurt Motor Show in September, we’ve headed to Ireland’s beautiful Wild Atlantic Way in a C2 GTS to take stock of what we’ve garnered from the 991 so far.

In part one of our review we looked at the performance of the 991, and later in part three we’ll look at the all-important driver experience garnered from piloting the latest-generation 911. Under our scrutiny today though is its chassis, and it’s here where much debate persists over the 991’s integrity as a bona fide Porsche 911.

The big issue lies in engine placement. For the 991, its flat six engine is placed more on top of the rear axle, rather than past it. This calls into question just how ‘rear engined’ the 991 actually is, especially when compared to the full-bodied rear-engined nature of every single Porsche 911 that preceded it. As well as the engine’s incremental shift forwards, the ‘mid-engine’ feel is supposedly exacerbated by the 991’s extended wheelbase, which is 100mm longer than that of the previous generation 997.

The 991 is 100mm longer between each axle than the 997, contributing to more of a 'mid-engine' feel over other generations of 911

So how does this transcend onto the road? Well, yes, the 991 does feel distinctly more mid-engined as such, meaning you can’t pivot the car from its rear in the same way you can a 997 (or 996, or 993, or 964, etc…). However, there’s no question the 991 benefits from an improved balance, particularly through corners. And, as Josh, Total 911’s Features Editor, discovered after a week with a 981 Cayman GTS, it’s not until you drive a true mid-engined Porsche that you realise the 991 still has textbook 911 handling characteristics woven into its DNA, where it’s still keen load up onto its rear haunches under acceleration and naturally understeer into a corner, forcing you to work hard to get that nose tucked in.

The adjustments in layout have brought out the best of both worlds for a serious 911 driver, then, and after a combined 20,000 miles of 991 experience between us, we at Total 911 are won over by these key changes.

It may have moved forward slightly but the 991 is  still a gloriously rear-engined sports car

Pleasingly, the handling remit is similar for both 2WD and 4WD 991 Carrera variants too. That’s the beauty of an all-wheel-drive 911: it still feels like a RWD sports car, though in fairness this was the same for the 997 too.

The clever torque distribution screen on the digital fourth pod is a useful tool for showing you how intelligent the 991’s system is in distributing power between the front and rear axle, giving you more of a rear bias exactly when you need it, and throwing more power forwards when required. There are times when the extra grip of a 4WD 991 is keenly felt, and in the wet the car feels unshakeable while not dumbing down the involvement that all special sports cars should possess.

Lastly, when it comes to speccing your 991, we strongly advise you to consider Porsche Dynamic Chassis Control. It may be pricey at £2,185 but it’s oh-so worth it. Utilising hydraulically actuated cylinders to effectively spread the load of the car through both front and rear anti-roll bars, it means the car is naturally better balanced through corners, allowing you to simply take them as if you were on rails.

Some say PDCC takes away too much feel, but we think Porsche have expertly retained just enough to ensure the driver can load up the car through a turn without being desensitised as to its permissible limits. It’s just one component of an exquisitely accomplished Porsche 991 chassis setup that’s a marked evolution over the 997 – while still unquestionably a 911.



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