16.11.1998

MULTIPLA: ENGINES


On many cars, engines determine the personality of versions within the range (economical, sporty, etc.). The approach is completely different on the Fiat Multipla. The engines were specially selected to adapt to this car's innovative brief: a car that is easy to drive, comfortable, dynamically safe, with respect for the environment and designed today for traffic conditions of tomorrow.

The choice offered by the five Fiat Multipla engine versions is not between different performance levels but between different fuel supply systems.

This is another breakthrough for the model: the Fiat Multipla is the first car to be created with petrol engines (1.6 16v), a diesel engine (1.9 JTD), a methane engine ('blupower'), a methane-petrol engine ('bipower'), and a petrol and electric engine (hybrid).

Like all Fiat engines, the Fiat Multipla power units ensure refinement, good performance and low fuel consumption. They also meet environmental protection specifications with plenty of room to spare. Noise levels are maintained below 74 dB and emissions levels are well below EU Stage II limits.


1.6 Torque 16v
The Fiat Multipla petrol power unit is a 1.6 16v 1581 cc unit. It belongs to the family of 'torque' engines, which owe their name to their ability to deliver a well-rounded and smooth torque curve. The engine offers lively performance and a balanced, flexible and satisfying drive. Everything one would expect from an engine destined to satisfy the needs of a wide-ranging public which will use the vehicle equally on mixed routes and on the motorway.

The result is 103 bhp (76 kW) of maximum power obtained at 5750 rpm and 14.7 kgm (144 Nm) of maximum torque at 4000 rpm. Almost 85% of this pulling power can be called upon through a wide range of speeds, from 2300 to 5800 rpm. The performance figures are everything one would expect and they can be summarised as 170 km/h at top speed in fifth gear and acceleration from 0 to 100 km/h in 12.6 seconds. Fuel consumption measured according to ECE+EUDC standards are 8.6 l/100 km.

This engine is 'supersquare': its bore and stroke specifications are 86.4 and 67.4 mm. The cylinder head incorporates four valves per cylinder, with twin overhead camshafts controlled by a toothed belt. The tappets are hydraulic and allow automatic valve adjustment. The toothed belt tensioner is also automatic.

The multivalve design increases air flow and thus power and torque. This brings the benefit of more compact combustion chambers. For the same volume, the area exposed to gas is lower and therefore heat exchange with coolant is lower. This improvement is translated into lower fuel consumption for the customer.

The specific cylinder head cooling circuit also ensures system efficiency for greater power unit reliability and durability.

The intake and exhaust ports on the 1.6 16v were computer designed (CAD-CAE) using fluid dynamic simulation programmes to ensure effective mixing and load distribution between cylinders. The intake manifold also features long branches (400 mm) to improve power delivery at low and medium engine speeds.

The integrated ignition-injection system is a Weber-Marelli multi-point system with static ignition and miniaturised injectors. It is controlled by a new management unit with high capacity and processing speed, which ensures a smooth drive and precise emission control under all driving conditions. Selective knock control (cylinder per cylinder) ensures higher engine performance and total reliability even in the case of operating anomalies (e.g. use of fuel with a lower-than-specified octane number).

Other distinctive features of this power unit are pistons designed to reduce noise levels and cylinder liner treated with a plateau finish which insures better lubrication and lower engine oil consumption.


1.9 JTD
The turbodiesel unit is the 1910 cc 1.9 JTD unit with Unijet direct injection system. Due to electronic control of pump and injectors, this type of common rail system is able to adjust the amount of fuel taken into the cylinders by using a very high injection pressure regardless of engine speed. It is also able to control very small quantities of diesel to carry out a pilot injection or pre-injection ahead of the main injection for smoother, less 'rough' combustion.

The result is a highly reliable engine capable of superior performance. Its fuel consumption is reduced by some 15% compared to power units with a pre-chamber. This power unit also ensures a high level of comfort characterised by no vibration and a level of noise until recently inconceivable for a diesel engine.

The variable geometry Garrett turbocharger alters vane angle to speed up or slow down gas speed to adjust turbine rotation speed and thus turbo pressure effectively. It exploits exhaust gas energy as effectively as possible to adapt to the various engine service conditions. When combined with an intercooler, it ensures the 1.9 JTD unit a high power output (105 bhp - 77 kW at 4000 rpm), excellent torque at low speeds (200 Nm equal to 20.4 kgm at 1500 rpm) and great driving flexibility.

When fitted with this engine, the Fiat Multipla reaches a top speed of 170 km/h, accelerates from 0 - 100 km/h in 12.4 seconds and pick-up in fourth from 60 to 100 km/h occurs in 9.7 seconds (14.9 seconds in fifth gear from 80 to 120 km/h). Fuel consumption measured according to the new ECE rule (urban route), plus EUDC (out-of-town route) is low: 6.4 l/100 km.

The 1.9 JTD design features four cylinders with two valves per cylinder, parallel and vertical, driven directly by a single overhead camshaft. The engine contains no pre-chambers because the entire combustion process occurs in the combustion chamber within the piston. The light alloy cylinder head features pistons with an 'omega-shaped' combustion chamber and screw-shaped intake port that swirls the air around for more effective combustion. The crankcase is in closed-deck type cast iron, i.e. with integral cylinder liners and intermediate cooling.

Another important feature of this power unit is a dual damped flywheel (DVA), which ensures a very smooth drive. Consisting of two masses, one mass is attached to the crankshaft and the other to the gearbox mainshaft, the system reduces vibration at low speeds and transmission noise to increase driving comfort.


METHANE POWER UNITS
Why methane Fiat Auto was the first manufacturer to offer a dual fuel system vehicle produced in a factory and sold through the normal sales network: the Marea Bipower. Now it is the first manufacturer to launch two versions specifically designed to run on methane or compressed natural gas (CNG), as it is otherwise known. These are the Fiat Multipla 'bipower' and the Fiat Multipla 'blupower'.

Many reasons influenced our decision to produce two engines. Apart from being a widely available energy source (world reserves are higher than oil reserves), methane is a clean fuel and thus consistent with Fiat policies - we have been concerned with green issues for some years. Compared to petrol, methane does not generate benzene or particulates during combustion, and reduces carbon dioxide emissions by some 25% and emissions of uncombusted non-methane hydrocarbons by 95%. It is therefore able to satisfy the toughest limits in the world, i.e. the Californian standards governing ULEVs (Ultra Low Emission Vehicles).

The financial benefits are also undeniable. This market is therefore currently limited in volume and territorial coverage but is certainly due to expand. This growth will be accelerated by the arrival of the Fiat Multipla, a car destined to bring about a leap in quality within the sector.

Fiat Multipla 'bipower' and 'blupower' The Fiat Multipla is the first vehicle to offer two true methane versions at launch. The new model has not been simply adapted to work on methane as well as on petrol (as is the case with petrol vehicles transformed after sale) but has been designed and developed specifically to be fitted with methane supply systems.

The two versions do not just follow in the tradition of the Fiat Marea bipower but represent a natural development from that car. On the Fiat Multipla, the decision to use natural gas does not affect the space inside the car or its driving range. The flat, high vehicle floorpan means that the cylinders can be positioned beneath the floor, outside the passenger compartment.

The range offered by these two versions of the Fiat Multipla is also extensive: up to 500 kilometres for the 'bipower' (which offers the same range when run on petrol) and up to about 700 for the 'blupower'.

Natural gas is loaded at a pressure of 200 bars into 4 mm-thick steel cylinders. The Fiat Multipla 'bipower' is fitted with three (for a total of 164 litres) while the 'blupower' is fitted with four (216 litres). These considerable volumes are due to the properties of the fuel itself. Four litres of compressed methane are necessary to produce the same energy as a litre of petrol.

Fuel system. Methane flows from the cylinder through pipes to a reduction unit fitted in the engine bay, which reduces pressure from its original level of 200 bars to about 9 bars. The gas then flows into four injectors. The fuel system of both Fiat Multipla methane-driven 1.6 Torque 16v engines is innovative compared to the system used on converted cars currently available on the market. The power units are fitted with injectors specifically designed for this fuel. The 'bipower' engine comes with two separate fuel systems, which are managed by a single phased sequential multipoint control unit.

Specific features of the two versions. Compared to the petrol engine, the 'blupower' offers different timing and a higher compression ratio. These characteristics are unchanged in the 'bipower' power unit, which is designed to work on both fuels. The 'bipower' version normally runs on methane and the driver can choose to switch over to the petrol option at any time. In two cases, however, switching is automatic: for a few seconds the first time the car is started up after refilling to prevent damage to the petrol injectors caused by prolonged inactivity - and when the methane is about to run out.

Catalytic converters. Both Fiat Multipla methane versions are fitted with catalytic converters specially designed for this fuel. Methane which emerges from the combustion chamber unburnt burns at a higher temperature than hydrocarbons produced by petrol. The catalytic converter temperature must also therefore be higher. In order to achieve this result, the catalytic converter in the new model's exhaust system is very close to the engine exhaust manifold. Compared to petrol units, the methane version catalytic converter uses a higher quantity of noble metals to promote the appropriate chemical reactions.

Safety. The Fiat Multipla 'blupower' and 'bipower' fuel system is also much safer. Firstly, due to the intrinsic properties of non-toxic methane, its float rate is high (i.e. it disperses into the air very quickly) and it catches fire at twice the temperature of petrol and diesel vapours. The Fiat Multipla methane versions also incorporate a set of safety devices that minimise risk in the case of impact or failure.

- Two solenoids isolate the part of the pipes into which high pressure methane flows. One is located on the reduction unit, the other on the fitting of each individual cylinder. They are connected to the inertia switch and block methane flow in the event of impact. They are both shut-down when the car is not methane driven.

- A system limits methane flow when an excessive quantity of gas emerges due to an anomaly or piping failure. Located inside the cylinder, it also cuts in if the solenoid is broken due to impact.

- If the temperature increases for external reasons, a fuse pad totally eliminates the danger of excessive pressure rises by venting (in the form of a limited, controlled flow) the methane contained in the cylinder. The Fiat Multipla 'blupower' and 'bipower' both pass fire tests with flying colours: no flame increase was noted due to controlled methane release when a car was set alight with its cylinders full.

- Finally a check valve on each solenoid prevents methane flowing back to the filler cap.

The mechanical system of the new model was also designed specially for these engines. The suspension settings are different to that of petrol and diesel versions to ensure excellent roadholding and maximum comfort. The cylinders are also protected by a guard to prevent damage by gravel or other factors.


FIAT MULTIPLA HYBRID
A reduction in environmental impact is one of the crucial factors considered when developing new models and Fiat Auto is working in several directions to this end. Apart from the Fiat Multipla 'blupower' and 'bipower', it now also offers a third alternative to conventional engines: a hybrid Fiat Multipla, which will go on sale at the end of 1999.

In hybrid cars, an internal combustion engine is connected mechanically or electrically to an electric engine, which can aid or replace the main engine under different service conditions. The electric engine is constantly powered by batteries and the batteries are powered by an electric generator if necessary.

On the hybrid Fiat Multipla, the internal combustion engine is petrol-driven (the 76 kW 1.6 16v Torque unit) and the electric motor is triple phase and asynchronous (30 kW). The batteries are metallic Nickel-hydride, with high energy density (70 Wh/kg, 19 kWh total). The generator consists of a high power alternator (15 kW) complete with current rectifier.

Power steering, brake servo and air conditioner are electrically powered. The electronic system that controls the drive components and the Inverter (i.e. the converter that transforms direct current delivered by the battery to triple phase alternating current taken up by the engine) are located in the console between the two front seats. The batteries are secured beneath the floorpan in a central position. The recharging lead socket is on the left rear side. The operating mode selector is on the facia and selection can be repeated on the instrument panel, which also features a battery charge status gauge.

The hybrid Fiat Multipla is a true multimode car due to its dual input Selespeed gearbox and automatic clutch, which connects the engines to the gearbox in different combinations. The car is indeed able to work in two modes: - hybrid: when both electric motor and petrol engine work simultaneously and both help propel the car forward; - electric: when the Fiat Multipla is propelled solely by the electric motor, with the internal combustion engine off and disconnected.

The decision to make the car work in hybrid or electric mode is taken by the driver, who can operate the selector on the facia at any time.

Let's take a closer look at the two operating modes:

Hybrid. Both engines act in parallel on the wheels. A sophisticated electronic system distributes the power delivered by individual engines in order to exploit the different characteristics of each to the full. Although the electric engine is less powerful, it delivers a high torque from take-off, while the internal combustion engine develops high power with reduced fuel consumption while running at an almost stationary speed. At start-up, therefore, the car is driven by the electric engine alone. The petrol engine then cuts in and drives the car at constant speed up to a maximum of 150 km/h. During pick-up and over-run (transient states), the petrol engine is assisted by the electric engine, which improves pick-up and saves energy during over-run and braking. During hybrid operation, the driver can call on four speeds plus reverse from the Selespeed gearbox.

Electric. This is the ideal mode when driving around town because it is noiseless with very low emissions (the Fiat Multipla is a ZEV, Zero Emission Vehicle). When this mode is selected, the car is driven by the electric engine alone because the internal combustion engine is off and disconnected. Top speed is 80 km/h and the Selespeed gearbox offers two speeds plus reverse. Range is 70 kilometres over an ECE cycle. The batteries may be recharged at any time from the normal electrical mains through the on-board battery charger.
When this is not possible and the batteries are nearly flat, electrical EA (Extended Autonomy) mode is implemented automatically. Under these conditions, both engines are operational but are used for different reasons. The car is driven by the electrical motor alone, while the internal combustion engine works at stationary speed to drive the battery recharging generator. This mode is turned off automatically as soon as the battery charge is high enough. When the hybrid Fiat Multipla works in this third mode, it may be considered an EZEV (Equivalent Zero Emission Vehicle). Exhaust emissions are the same as the overall emissions produced by an electrical vehicle (ZEV), even counting the electrical energy production process within a thermoelectric plant.


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