With over 700 examples sold each month in Brazil during the last quarter, the innovative Fiat Siena 1.4 Tetrafuel has exceeded Fiat Automóveis' sales projections by an excellent three-and-a-half times. When the ground-breaking new model was launched onto the Brazilian market in October of 2006, it was expected to see average sales of around 200 units a month.

The Fiat Siena 1.4 Tetrafuel is the first passenger car in the the world to be able to use four different kinds of fuels (moisturised alcohol; Brazilian gasoline which is made up of 25 percent alcohol, pure gasoline and natural gas). Besides this, the great technological innovation of the model is the fact that a single electronic control unit which was developed by Magneti Marelli manages the use of fuels in a seamlessly integrated manner, changing the fuel required without any interference or input from the driver. In other words, who decides which is the most appropriate fuel to be used at any given moment is the car's electronic control unit and not the driver who does not need to press any buttons in the dashboard to manage the system. The system's main priority is to achieve economy so the first choice of the system is GNV as the main source of fuel, but when the system detects a situation that requires extra torque, for example to overtake another car or to climb up a ramp, it switches to alcohol or petrol automatically.

The base of the trunk has been reinforced to receive the fixation and the supports for the cylinders of GNV, each one has a total capacity of 6.5 cubic meters of gas with 200 bar. The front and rear suspension units have specific buffer springs and shock absorbers to keep the required distance from the ground, but beyond these changes, modifications in the braking system have been made to preserve the same performance and characteristics of the standard model.
 

The instrument panel is fitted with detectors to alert the driver of a low level of GNV and the level of pressure of the cylinders, as well as alerting them to damage in the system, the level of external temperature and an obligatory Trip Computer. The Siena Tetrafuel has robust mechanisms in the area of passive safety, to avoid greater damage in case of an accident, while the positioning and the fixation of the two GNV cylinders have been projected to overcome all crash-tests and fire tests required, achieving the same levels of safety of the standard model.

The components of the system for the natural gas were built and tested for not allowing any leaks, but if however a pipe breaks a safety mechanism immediately shuts off the flow of GNV. The system has also a relief device for any overpressure occurring in the cylinder, allowing the GNV to safely leak into the atmosphere; and in case of a collision it blocks off the flow of the gas.

The use of GNV in larger transportation vehicles such as taxis, buses and light commercial vehicles is increasing very rapidly, and a similar pattern is occurring amongst private drivers, in Brazil, all being led by its economical benefits and environmental aspects. Fiat is also the first automotive brand in the country to offer a complete system with the same warranty as is offered to its standard models.

by Claudio Perlini