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05 – Espace technique

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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Porsche Remote Park Assist – Une nouvelle fonctionnalité facilitant le parking

Porsche dévoile au travers d’une vidéo son nouveau système Remote Park Assist, permettant de fortement aider le conducteur d’un nouveau Porsche Cayenne à se garer dans différents cas de figure et parfois sans être dans le véhicule. Présenté au salon de Francfort 2017, le Porsche Cayenne continue de surprendre avec ses technologies embarquées. Porsche vient …

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As If by Magic

Driving a Porsche is an experience. So is parking one. With a driver—or without.

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How Tire Pressure and Inflation Affect Your Porsche’s Performance

For those of us who drive on the street, tire pressure probably doesn’t get a lot of consideration. Porsche includes recommendations in the manual, and frankly, why not use them? Of course, when driving deviates from the daily grind, tire pressures become a lot more important. Whether using your Porsche for a track day, autocross, or road rally, more extreme situations than normal may require deviations from « normal » tire pressures.

The video above from Engineering explained does a good job covering the fundamentals of tire pressure and performance in the dry and in the wet. The video also covers important points such as how temperature affects tire pressure, and how tire pressure can affect tire wear.

991 Tire Pressures

The Modern 911 Perspective

The chart above is from the owner’s manual for 2017 911 Carrera 2 models. Let’s dive in to this chart a little. The 911 is rear engined, and runs a staggered wheel and tire setup, and this drives the tire pressure specification. The high percentage of mass over the rear axle requires greater tire pressure than the fronts for two primary reasons. The first is to carry the load of the rear mounted engine, and the second is to mitigate the oversteer inherent in the layout.

991 Carrera S

Lowering rear tire pressure would increase oversteer, and increasing it further would increase understeer. The opposite tire pressure to understeer/oversteer relationship holds true for the front of the car. In a modern 911, the wheel and tire setup is entirely designed around bringing oversteer in line. In addition to the tire pressure differential, the 911 runs a much wider tire at the rear than at the front(this is true in both RWD and AWD models).

944 Tire Pressure

In my case, this is no longer relevant because I am not running stock sized wheels.

Tire Inflation and Older Porsche Models

Porsche specifies a cold tire inflation number for all models. Into the 1990s, this information was generally on a little yellow tag under the fuel filler door, though it is also in your owner’s manual. These tire pressures are designed to tame the cars’ handling somewhat. In a stock, naturally aspirated 944 with the same size tire at all four corners, this was done by reducing the tire pressure slightly at the front end. Tire Rack has a helpful chart which helps to illustrate how several suspension setup changes, including tire pressure, can affect vehicle handling.

Unlike a 911, a 944’s mass is nearly balanced from front to rear. With equal sized tires at both ends, simply dropping tire pressures at the front will induce some understeer. While this will make the car more docile for inexperienced drivers, it is also easy to counteract simply by raising tire pressures on the front axle. To get the same net effect in a 911 requires both a differential in tire pressure and width. This is part of the reason early 911s have a much more well deserved reputation for tricky handling than later cars. Very early 911s use the same width tires front and rear. As time went on, the rear tires became much wider relative to the fronts, while weight distribution remained approximately the same.

Porsche 356 Technical and Restoration Guide

The Classical Perspective

Fortunately, these truths are pretty much universal. If you look back in the 356 Registry magazine archives(which I have a portion of in their Technical and Restoration Guide), you’ll see the same tire pressure advice. In reference to setting a 356 up for autocross, in Volume 8, Issue No. 3, Bob Napier writes:

« … with this setup I usually run 36PSI in the front and 34(PSI) in the rear. The higher front pressure partially offsets the low speed understeer tendency, and, on a real tight course, I might drop to 33 or 32 in the rear in an attempt to get the rear to come around. »

So whether your Porsche is new or old, monitor your tire pressure for optimal handling!

Resources on Tire Pressure and Setup for your Porsche:

 
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Porsche’s Self-Parking Tech: Autonomous Future Or Convenient Tech?

Porsche first announced this new self-parking technology earlier this year, and it will begin to roll out across Europe in the next few months with further market availability after. They’re billing this Remote Park Assist tech as a boon for city dwellers and suburbanites alike, as you can reverse into a parking spot that is super tight without being in your Porsche. This makes it easier to get out of the Porsche while the doors are clear and then reverse your Cayenne into the space where it would have been more difficult to extricate yourself.

The Cayenne will even help you find your parking space, as the technology suite includes a feature that detects and highlights parking spots that the Porsche SUV will fit in without issue. The system works with spots on both sides of the street, and includes parallel and right angle parking. Once you’ve found a suitable parking space, you can hop out of the vehicle and control the action from your smart phone’s touch screen. Just press and hold the OK button until the Cayenne has finished its parking actions.

Porsche has added this technology thanks to a highly complex system of electronic aids that completely take the driver out of the equation. According to Porsche’s press release on the matter, four extra high-tech processors coordinate the parking job out to twenty more control units. Four cameras on the Porsche help produce a 360-degree view of the Cayenne in real time, and the computer uses an additional twelve ultrasonic sensors. The system, as Porsche explains it, builds an impact-buffering cocoon around the SUV to optimize caution, precision, and safety. If the system detects a pedestrian, a high curb, or a parking bollard near the vehicle, it will intervene and stop the parking process, or make automatic adjustments as necessary. Of course, the parking process can be paused by remote control of the user at any time.

Are We Users or Drivers?

Herein lies the crux of the problem, Porsche has begun thinking of customers as « users » instead of « drivers ». Right now these self-driving features are focused on convenience and sparing you, the owner of the Cayenne, a few extra seconds and perhaps a little discomfort. « Where is the harm in that?, » you might say. How much longer will we retain control of our own Porsches? The company has come out against full autonomy in the past, but seems to continually re-adjust their stance on the matter, gradually moving toward the idea. How long will it be before Porsche introduces autonomous driving technology for highway and city surface streets? Will they bill it as an autonomous way to get to your favorite driving roads or race track? If that happens, will the driver ever have full control of their Porsche again? What are your thoughts on an autonomous Porsche?

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