Loosely translated from the original German

World first: Porsche builds aluminum wheels using hollow spoke technology. Turbo wheel more than 20 percent lighter

In order to make aluminum wheels as light as possible, Dr. Ing. h.c. F Porsche AG has developed a new technology that allows wheel spokes to be hollow. This technical world first is being used for the first time and as standard for the wheels of the new 911 Turbo.

The wheels, which represent part of the unsprung mass and thus have a negative impact on vibration comfort, improve vehicle comfort, handling properties, ABS control characteristics (better response) thanks to their significantly lower weight and also reduce fuel consumption.

The weight reduction of the wheels of the 911 Turbo is impressive. The 18-inch high and eight-inch wide front wheel is 2.6 kilograms or 23 percent lighter than conventional production. The weight of the ten-inch wide rear wheel is reduced by 2.9 kilograms or 20 percent. All four wheels therefore weigh a total of 40.8 kilograms, eleven kilograms less than before.

The hollow spoke technology means that the 911 Turbo can be fitted with wheels in the modern, but construction-related heavier, Softline design as standard. The look of this type of rim is characterized by the soft transitions of the spokes attached to the outer edge to the deep center, which also has the advantage of being easy to clean.

The rim and bowl (star) of each wheel are two separate components that are only permanently connected to one another using a special welding process (friction welding). The bowl is made star-shaped and hollow using the new Porsche technology in a low-pressure casting process, whereby a thinner wall thickness than that of a conventionally manufactured wheel could be achieved. Areas of the wheel that are subject to particular stress are reinforced with ribs. A significantly higher component rigidity can be achieved using the closed spoke profiles.

By separating the two wheel elements, the rim base can be manufactured without a complicated mold tool. The width of the rim formats can also be varied as desired. Since the rim and the bowl have rotationally symmetrical connection surfaces, friction welding is the ideal way to connect the components. The process guarantees the highest quality, reproducibility, monitorability and the best precision. In principle, friction welding is not a new development in the automotive industry, but has not yet been used in the field of series wheel production.

Porsche AG is the first vehicle manufacturer in the world to use aluminum wheels manufactured using hollow spoke technology as standard. The Porsche 911 Turbo, which will be on the streets from April 1995, will be fitted with hollow spoke wheels as standard. Porsche also offers this new process to other companies through the customer development department in Weissach, Porsche Engineering Services (PES).

Porsche was the first German car manufacturer to develop an aluminum wheel in the mid-1960s. The popular Fuchs rim in the star design became the identifying feature of the sporty 911 S from the 1967 model year onwards. The distinctive rim adorned the 911 models in various sizes until the 1980s.

On-board diagnosis II as standard New exhaust gas monitoring system for the Porsche 911 Turbo

Dr. Ing. h.c. F. Porsche AG, Stuttgart, is the first vehicle manufacturer to set standards worldwide by using the newly developed and vehicle-installed exhaust gas monitoring system OBD II (second generation on-board diagnosis) in the new 911 Turbo. The company is thus making a further contribution to environmental protection - after introducing the particularly efficient and long-lasting metal catalyst with lambda sensor, which Porsche was the first vehicle manufacturer in the world to use.

With this step, the sports car manufacturer is underlining that not only is compliance with the applicable environmental regulations a matter of course, but that Porsche also introduces improvements before they become law. The constant optimization of the environmental friendliness of the product is a high priority at Porsche and is one of the company's central principles. With these guidelines in mind, Porsche AG is committed to ensuring that sports car construction and environmental compatibility are not a contradiction.

Sobering figures

Studies by the EPA (environmental protection agency) in the USA clearly show that regular inspection and maintenance of the existing pollutant-reducing systems can reduce emissions by 30 percent. 15 percent fewer pollutants are possible with cleaner fuels and only two percent with a further reduction in the limit values for new vehicles. Based on these surveys, the legislators in California introduced On-Board Diagnosis I, which Porsche has been using since model year 1991. This is an electronic functional test of a few components such as the injection system.

From model year 1996, all manufacturers must equip their US models with the much more comprehensive OBD II. As a pilot project, Porsche will equip the 911 Turbo, which will be available from April 1995, with the new technology from the start, not just in the USA but worldwide. At the same time, the sports car manufacturer is promoting the desired global harmonization of legislation. All 911 Turbos produced - regardless of the country in which they are sold - have the same exhaust technology.

Advanced technology

The central monitoring unit for OBD II in the 911 Turbo is the latest generation electronic engine management control unit, the Bosch Motronic M 5.2. The scope of control and testing made it necessary to increase the computer capacity several times over. In fact, three quarters of the computer software is already used to reduce consumption, reduce exhaust emissions and diagnose errors. In addition, the sensor system must be supplemented by two additional lambda probes (for monitoring catalytic converters).

The OBD II detects malfunctions or defects in the catalytic converters, the lambda probes, the fuel supply, the secondary air injection and the tank ventilation. Engine misfires are registered on the one hand with regard to an increase in emissions and on the other hand with regard to the risk of catalytic converter damage. In addition, the OBD II also monitors all other vehicle components that are connected to the control unit and could cause an increase in emissions in the event of damage.

Deviations from the target value are stored by OBD II, corrected if possible, and displayed to the driver by a warning light. The driver should then immediately contact a customer service department. The workshop can carry out quick and reliable diagnoses with unequivocal detection and rapid replacement of the faulty components.

The advantage of OBD II is that it detects and reports errors immediately. Above all, the scope of the test is considerably greater than with the emissions test (AU) that is common in Germany and the risk of misdiagnosis is lower. With the AU every two years, errors and defects remain undetected for a long period of time, provided that there are no noticeable engine malfunctions associated with them that prompt the customer to visit the workshop.

Porsche was there from the start

As early as 1966, Porsche built an exhaust gas roller test bench, which was the first in Europe to receive approval from the American environmental agency to carry out official exhaust gas tests. With this complex step, Porsche clearly committed itself to environmental protection and repeatedly took on a pioneering role. Innovative technologies such as electronically controlled injection systems, optimal mixture preparation, variable valve control and the optimally designed combustion chamber led to low values for raw emissions and specific fuel consumption. In addition, there were secondary measures such as exhaust gas aftertreatment, turbo technology and the use of specially coordinated intake pipes.

Porsche has a great deal of experience in exhaust gas purification of high-performance engines. Since the introduction of the catalytic converter in Europe, the variants with and without an exhaust gas purification system could be offered with identical performance, which led to rapid acceptance by buyers. Porsche also demonstrated the durability of the catalytic converters on the racetrack. As early as 1986, all vehicles in the "944 turbo Cup" racing series were equipped with the exhaust gas purification system.

In 1988, Porsche introduced the metal carrier as the main catalyst. This has significant advantages over conventional ceramic catalysts. A metal catalyst is less susceptible to breakage and can tolerate higher exhaust gas temperatures, which automatically occur in high-performance sports cars. In addition, the thin honeycombs inside the catalyst have the advantage that they heat up quickly. This means that the metal catalyst quickly reaches the operating temperature of around 250 degrees, at which point the exhaust gases are optimally converted.

Porsche was also one of the first car manufacturers to exclusively use a regulated catalyst with a lambda sensor. In 1988, Porsche was one of the first vehicle manufacturers to introduce the heated lambda sensor in order to optimize its functionality.

With these technical solutions, Porsche has made a significant contribution to the development of the catalytic converter and thus made a valuable contribution to environmental protection. With the standard worldwide use of on-board diagnostics II in the new 911 Turbo, the sports car manufacturer is once again moving forward - for the sake of the environment.

Exhaust center to be set up in Weissach

Further evidence of Porsche's acceptance of environmental issues and an indication of the technical equipment is the decision of the car manufacturers Audi, BMW, Mercedes-Benz and Volkswagen to set up the German exhaust center in our research and development center in Weissach. Subject to the approval of the Federal Cartel Office, the above-mentioned car manufacturers want to work with us to develop new, series-ready processes through joint research, with the help of which the implementation rates of exhaust gas purification systems can be increased from the current 90 percent to almost 100 percent of hydrocarbon emission avoidance.

These developments require an above-average amount of effort that can only be achieved jointly. This joint venture will enable automobile manufacturers to develop expert know-how more quickly and cost-effectively. This will contribute to increasing international competitiveness.