An Era of Variable
May 2003

Since the beginning, car engineering was a matter of choosing the right materials and construction to achieve the target - performance, handling, comfort, space, whatever. Car engineers knew that no matter how clever they work, there were always compromises. For example, a chassis designed for good handling must result in compromised ride quality. 

But then the automotive world was changed in 1987 by Porsche 959. This car introduced a new concept - Variable. Everything in the car was variable to suit different conditions of use. Its twin-turbo engine was variable, using only 1 turbo at low rev and 2 turbos at high rev to achieve both low lag and high boost. Before that, the size of turbocharger used to be a compromise between power and drivability. Its suspensions had variable damping, offering 3 settings to suit different kinds of road or speed. Similarly, the ride height was also variable. It can be raised to ride on rough road and lowered on highway to improve stability and drag. The 4-wheel-drive system was variable, too. Torque split between front and rear axles can be adjusted to suit different conditions. When 959 accelerated, initially 80% torque went to the rear wheels which had most traction due to weight transfer, then gradually reduced to 60% when acceleration force tailed out. On slippery surface like gravel or snow, it could be changed to 50:50 to provide maximum traction. 

The Variable Technology of 959 foresaw today’s mass production cars. Now you can see Variable this and that everywhere: variable intake manifolds (short runners for high speed, long for low speed), variable valve timing (late timing for low speed, early timing for high speed), air suspensions (i.e. variable spring rate), adaptive damping, active anti-roll bars (see BMW 7-series and Citroen’s Activa), active differential (e.g. Lancer Evo VII), active yaw control (also Evo VII), ESP stability control, speed-sensitive and variable ratio steering rack, automatic or sequential gearboxes with sport / comfort / winter mode, electronic throttle with sport / comfort mode, variable rear spoiler.... these variable things make cars more versatile. Want comfort? OK, change the setting of suspension, transmission, throttle and steering to comfort mode. You even need not to press a button, because clever electronics already sensed what you want by detecting your driving style. Once you floor down the throttle, or turn the steering wheel quickly, the settings will be reverted to sport mode and you will get tight body control, sharp throttle and gearbox response while the rear spoiler is raising to generate downforce. So easy, everybody can drive fast. Whether the driver is Schumacher or Zoo’s Monkey is not important. 

With variable technology, chassis engineers became a boring job. Innovative thinking like Colin Chapman is no longer useful, because variable technology can largely compensate the inherent flaws of a poor chassis. Nose heavy? we have active suspensions to reduce nose dive under braking. High center of gravity? active body control can limit roll to just a few degrees. What chassis engineers do now is to test their variable systems repeatedly to sort out the software. That’s a hard but routine job. In contrast, in the days of Colin Chapman they were more likely to brainstorm a new chassis concept by sketching with an old pencil. 

Just when car makers - mostly German - thought they have achieved the impossible - eliminating compromises, they find their variable systems added hundreds of kilograms to their cars. A proper Variable performance saloon weighs about 1700 to 1800kg, so they need to install a bigger engine. Variable technologies also increases cost by thousands of pounds, making every new generation more expensive than their predecessors. 

That’s the compromise for eliminating compromises.

Mark Wan

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