When you imagine a modified Porsche you would never think of something like what you see in the images that illustrate this article, which looks like something out of a science fiction movie. This silver Porsche 928 was used to measure the sound of tires and that is why it has all those parts added in such a curious way.
The aim was to reduce engine and transmission noise as much as possible in order to measure tyre noise more accurately and to comply with noise emission regulations. A Porsche 928 was chosen because a lot of power was needed at low revs. This ruled out the 924 and 944 with their typical gearbox noise. The air-cooled 911 was also too loud. At the end of the 1980s, noise levels above 75 dB were not allowed – a real challenge for sports cars.
The appearance was not important, only the minimisation of noise sources from the engine and transmission, as well as the intake and exhaust sound. The radiator was mounted in front of the bumper, without the fan. The air intake was relocated in a large cylinder with the best possible insulation, like an intake silencer. From there, the pipes led to the engine in the fully encapsulated compartment. To ensure engine cooling when necessary, two fans housed in openings in the bonnet extracted the hot air at the push of a button.
The exhaust system gained a huge rear silencer fixed to the rear window, connected to the original exhaust with two pipes. At the bottom, the drive shaft was completely wrapped and the underbody insulated around the gearbox. The car was used for three decades, hence the wheel arches were enlarged to accommodate the new tyre sizes that were being mounted on the cars (in the images of the Porsche 911 991).
In addition, it was fitted with a very torquey V8 engine, different from the one fitted in the 928 GTS, designed to perform at high revs, which makes this Porsche even more special.
