Sign up for the newsletter
Sign up for the Stellantis Communications Newsletter and stay updated on all the news.
01 Sep 1997
Punto "Economy power" prototype at the 57th Frankfurt Motor Show
The 3.8 l/100 km prototype isn't an ecological dream car for motor shows but an experimental vehicle thanks to which it will be possible to develop devices that can subsequently be transferred to normal production vehicles.
Inspired by the criterion that lower fuel consumption also means lower emissions, the Fiat Technical Management and Fiat Research Centre's designers set themselves the objective of developing a vehicle that only consumes 3.8 litres of fuel every 100 kilometres. What's more, however, this objective included the stipulation that they could not use a specially designed prototype but only a popular car like the Punto. This difficult task was made all the harder by the simultaneous aim of achieving good driving characteristics and better performance (concerning acceleration, pickup and maximum speed) than that of the Punto with the same size engine in production today.
Having therefore rejected the easier approach of a pure research exercise on a laboratory vehicle with a small engine and correspondingly modest performance, they took the more difficult route that however reaps the benefits of the results obtained by bringing them to a standard production model.
This led to in-depth research to improve every aspect possible following three main lines of approach:
The drag coefficient is excellent if one remembers that, while retaining its lines, the prototype has a Cd·S of 0.49, 26% lower than that of the normal production vehicle. The credit's due to painstaking wind tunnel work that led to the adoption of new sideskirts, a modified front bumper, a rear bumper which has also been modified, and work around the wheels which, among other things, have aerodynamic arches. The door mirror design is also new and the rear lights have been modified too, featuring an aerodynamic lens designed to optimise air flow. The underbody of the vehicle is fully enclosed by streamlined body panels. All in all, therefore, there have been few changes. All of which, however, have precise objectives and have been tested extensively.
The Punto 3.8 l/100 km prototype weighs 840 kg, 200 less than the production Punto. This result has been obtained by making extensive use of sophisticated ultra-light materials such as magnesium, aluminium, titanium, carbonfibre and plastic polymers for the entire body and all the mechanical systems. The doors and tailgate are aluminium, for example, as are the shock-absorbers, struts and wishbones. The seat frames, gearbox, door frames and steering box are magnesium. The exhaust is in titanium and the steering column carbonfibre.
Other alternative technical solutions regard the following systems:
Inspired by the criterion that lower fuel consumption also means lower emissions, the Fiat Technical Management and Fiat Research Centre's designers set themselves the objective of developing a vehicle that only consumes 3.8 litres of fuel every 100 kilometres. What's more, however, this objective included the stipulation that they could not use a specially designed prototype but only a popular car like the Punto. This difficult task was made all the harder by the simultaneous aim of achieving good driving characteristics and better performance (concerning acceleration, pickup and maximum speed) than that of the Punto with the same size engine in production today.
Having therefore rejected the easier approach of a pure research exercise on a laboratory vehicle with a small engine and correspondingly modest performance, they took the more difficult route that however reaps the benefits of the results obtained by bringing them to a standard production model.
This led to in-depth research to improve every aspect possible following three main lines of approach:
- improving performance and fuel consumption through improved engine management (above all where power delivery is concerned) and an appropriate choice of gearbox ratios;
- improving the Cd, working on the vehicle's bodywork design without however taking this into the realm of impractically radical designs;
- reducing the vehicle's weight.
The drag coefficient is excellent if one remembers that, while retaining its lines, the prototype has a Cd·S of 0.49, 26% lower than that of the normal production vehicle. The credit's due to painstaking wind tunnel work that led to the adoption of new sideskirts, a modified front bumper, a rear bumper which has also been modified, and work around the wheels which, among other things, have aerodynamic arches. The door mirror design is also new and the rear lights have been modified too, featuring an aerodynamic lens designed to optimise air flow. The underbody of the vehicle is fully enclosed by streamlined body panels. All in all, therefore, there have been few changes. All of which, however, have precise objectives and have been tested extensively.
The Punto 3.8 l/100 km prototype weighs 840 kg, 200 less than the production Punto. This result has been obtained by making extensive use of sophisticated ultra-light materials such as magnesium, aluminium, titanium, carbonfibre and plastic polymers for the entire body and all the mechanical systems. The doors and tailgate are aluminium, for example, as are the shock-absorbers, struts and wishbones. The seat frames, gearbox, door frames and steering box are magnesium. The exhaust is in titanium and the steering column carbonfibre.
Other alternative technical solutions regard the following systems:
- Front suspension: having lowered the stance, it became necessary to develop a new mechanical cross member and new aluminium struts with mounting points for clamp shock absorbers; the stabiliser bar was optimised for effective operation by passing it over the cross member and connecting it directly to the shock absorbers using link rods.
- Rear suspension: swing axle system with springs under the floor pan and shock absorbers in the wheel arches.
- Engine unit suspension: centre-of-gravity suspension with reaction linkage on mechanical cross member.
- Transmission: tubular full live axle, optimised constant
- speed universal joint, dedicated tripod joint forming an integral part of the gearbox output shaft.
- Gearbox control: dual flexible cable solution.
- Steering column: magnesium monolithic steering column support; composite steering column, magnesium mechanical steering box guide and rack with optimised tooth profile.
- Brake system: optimised handbrake lever, new handbrake cables, new handbrake support, dedicated 180 diam. MMC rear brake drums.
- Fuel tank: the low fuel consumption of the vehicle has made it possible to reduce the fuel tank capacity without sacrificing range (including air bubble) developing a new 26 litre sheet steel tank.
- Exhaust pipe: new exhaust with rear single silencer and consequent reduction in heat shields.
- Rims: new rolled aluminium design obtained from a 9 mm disc.
- Starting system: new-design compact 30 Ah battery (semi-two-pole recombination system), adoption of 6 x 2.3 V super-capacitors with a capacity of 800 F each connected in series, which form a power buffer that is particularly useful for the stop and go starting function.
- Rolling components: adoption of 155/70-15 tyres developed with the following characteristics:
- geometrical dimension which tends to reduce tyre deformation in the contact zone;
- tyre profile and tread pattern designed to operate at 3 bar;
- use of 1% silica mixtures and other innovative materials manufactured without regard for all the limitations connected with industrial production;
- use of dedicated tread pattern;
- dedicated architecture and disregard for the limitations normally adopted in industrial manufacture;
- smaller bearings with low-friction seals.
- Efficiency: elimination of power steering and high
- efficiency alternator.