2002 Geneva Show: Rinspeed Presto

February 25, 2002

Rinspeed, a Swiss company that enlivens the Geneva Auto Show each year with outlandish creations that have included a sports car with a driving seat that tilts like a motorcycle and some way-out modified Porsches, has done it again. The company’s latest, which will be unveiled when the show opens early in March, is the Presto, a small sports car that can be extended and shortened as required.

No, really. If there are four occupants rather than two, the car can be extended to provide two extra seats; if the parking place you find is too small, the car can be compacted to fit. The difference between two and four-seater formats is just over 29 inches, with the car measuring a little over 118 inches overall in short form and a hair under 147.5 inches after expansion. The wheelbase in two-seater mode is 69 inches, and it extends to 116 inches.

Rinspeed Presto concept

Rinspeed Presto concept

What makes the transformation possible is a rear body section that slides in and out. It’s driven by a centrally located electric motor, which stretches the vehicle with the help of two mechanical screw-and-nut gears. The longitudinal members run on low-friction precision rollers and disappear like a drawer in the rear of the floor pan. To ensure absolute operational safety the extension mechanism also features self-locking safety latches. Despite its variable length the Rinspeed engineers insist they have succeeded in designing the adjustable Presto floor pan with the torsional rigidity necessary for a roadster.

Weirdly advanced

The concept is pretty weird in terms of its variable-length chassis, but there are also some advanced technical features. It’s powered by four-cylinder, 1.7-liter common-rail turbo diesel engine in dual-fuel configuration. It’s based on a Mercedes-Benz unit and provides future-oriented and highly environmentally friendly propulsion. The engine runs on a mixture of natural gas and diesel fuel at a ratio of 40 to 60. Natural gas is a very clean-burning fuel, which consists almost entirely of methane with sulfur content near zero. However, since a diesel engine has no spark plug to act as an ignition source, operation on natural gas alone is technically impossible.

The operating principle of the dual-fuel engine is simple: natural gas is injected into the intake air of the engine, and as in the production engine, the diesel fuel is injected into the combustion chamber. There it ignites a mixture of natural gas and air rather than just plain air.
To configure the turbocharged in-line engine for dual-fuel operation, a number of modifications are required, including installation of a tank for the natural gas and a gas-injection system. At the heart of the modifications is a reprogrammed engine management system. Should the system malfunction it reverts to the standard diesel-mapped ignition, thus offering the same level of reliability as the production car.

Dueling fuel
According to Rinspeed and Esoro, the Swiss engineering company behind the power unit, this technology has enormous potential for reducing exhaust emissions and fuel consumption. Emissions of nitrous oxides and carbon dioxide can be lowered by as much as 10 percent compared to the already extraordinary low level of the production engine. Particulate matter emissions can be lowered by up to 40 percent. With emissions this low the dual-fuel engine easily meets all existing and currently planned emission limits.
The dual-fuel engine is compelling proof that environmental protection and driving fun can go hand-in-hand: the four-valve engine develops maximum power output of 120 hp at 4200 rpm, and produces maximum torque of 165 lb-ft at just 1600 rpm. Performance is boosted accordingly: the 1907-lb quick-change artist accelerates from 0 to 62 mph in approximately 10.5 seconds and reaches a top speed of approximately 112 mph.

The package looks smart and it will do its job for Rinspeed by gaining valuable publicity in Geneva – but whether we’ll be driving round in variable-length ‘easy park’ vehicles is another matter. The dual-fuel engine, however, could have its place in the future of the automobile.

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