FACTfile - Alfa 147 (2004) – Page3

The 2.0 litre 110 kW engine

The Alfa Romeo Twin Spark engine has entered the history of the marque as one of its leading engines, with its unique combination of efficiency, excellent power-to-weight ratio, low emissions, exceptional torque and power spread and - an essential for all Alfa Romeo engines - a sound and character that is an integral part of the Alfa Romeo experience. For its installation in the Alfa Romeo 147, the Twin Spark unit was changed to suit its new environment.

Improvements over previous Twin Spark engines included:

1. Changes to the valve drivetrain.
2. Improved thermodynamics; the adoption of small diameter valves and ports together with a compact combustion chamber built for lower fuel consumption, particularly with low load and low speed.
3. The use of a metal cylinder head gasket that requires lower tightening torques and thus reduces power uptake by the timing system.
4. Other improvements allowed reduction of engine weight from a minimum by 3.0 kg. This was achieved by refacing the crankshaft and pistons.
5. Engine noise was reduced by cutting the weight of reciprocating masses to obtain a smaller shift in the centre of gravity and a consequent reduction in vibration during engine operation. This has been reduced still further through the adoption of two counter-rotating shafts.
6. An electronic throttle control, or fly-by-wire system, was also adopted to do away with a mechanical link between throttle and accelerator pedal. The engine electronic control unit, naturally acting upon the driver's request, governs throttle body opening to improve handling during acceleration and deceleration and also reduce fuel consumption and emissions.
7. The 2.0 Twin Spark engine also adopts a variable geometry intake system managed electronically by the injection control unit on the basis of engine service conditions. It therefore uses ducts of different lengths in different situations: longer at low rpm and shorter at high rpm. This device exploits 'ram' and acoustic resonance effects to ensure that the cylinder fills efficiently for improved engine performance.

These engineering improvements have produced a petrol engine that offers plenty of torque at low speeds: 90 per cent of the maximum value is available from 2,000 rpm. The 2.0 Twin Spark unit is the top of the Alfa 147 petrol engine range and balances top performance and driving flexibility to excellent effect. Variable geometry intake ports allow engine potential to be exploited to the hilt both in town traffic and on the motorway.

The Alfa 147 2.0 Twin Spark engine reaches its maximum power output of 110 kW at 6,300 rpm and delivers a torque of 181 Nm at 3,800 rpm. With this engine, the Alfa 147 reaches a top speed of 208 kmh and takes 9.3 seconds to accelerate from 0 to 100 km/h. Fuel consumption over a combined cycle is 8.9 l/100 km (ECE + EUDC). The figures are the same for both the Twin Spark manual and the 147 Selespeed.

The Alfa 147 gearboxes are silent, slick, sturdy and reliable. They allow rapid gear changes and ensure the generous engine performances can be exploited to the full. This result is due to careful choice of materials, precise assembly and machining and also meticulous testing at the bench and on the car.

Great attention has also been devoted to component installation in order to ensure the product meets design requirements. Pre-inspections are carried out in the factory followed by final electronic tests: operating load with the car standing still, efficiency, flexibility, clearances and so on. The Alfa 147 is also the first car in its segment to be fitted with a sequential gearbox with controls on the steering wheel, the 147 Selespeed.

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Alfa 147 gearbox choice

There are now three different gearboxes available in the Alfa Romeo 147.

The Twin Spark is available with a choice of a five speed manual or a five speed Selespeed. The 147 JTD is fitted with an all new six speed gearbox and clutch designed specifically to work with the torque characteristics of the new diesel engine and maximize its abilities.

The 147 2.0 Twin Spark (5 speed manual)
The Alfa 147's five-speed gearbox is noiseless, slick, sturdy and dependable. It allows fast shifts and ensures the generous engine performance is exploited to the full. This result is due to careful choice of materials, precision engineering and machining and also meticulous inspection carried out at the bench and on the car.

The gearbox uses a new twin-cable external gear control. This is made out of hi-tech materials (high-performing technopolymers) that are used for their different properties of strength, weight and self-lubricating capacity. The device ensures low noise levels and easy manoeuvres while also eliminating shaking and vibration of the selector lever. A Borg-Warner baulk ring synchronisation system reduces gear engagement effort significantly. The synchroniser is triple-cone for the first and second speeds and double cone for the third speed, the ratios most commonly used in town traffic.

The gears have high-meshing teeth and in addition fifth speed and final drive gear sets are machined to a superfinish following heat treatment. These features make component operation quieter and minimise drive transmission irregularities. Gears inside the gearbox are lubricated by ducted oil flows.

This offers many advantages: more effective torque transmission, less wear and easy to manoeuvre at low temperatures due to the use of synthetic oil that is relatively insensitive to heat fluctuations. The clutch pump is equipped with a plastic case, steel cylinder and plastic piston. A hydraulic coaxial clutch release control (CSC) is used on the 147 2.0 Twin Spark.

The CSC offers many advantages over a conventional hydraulic control where the actuator is positioned on the gear mount and controls a fork that in turn acts on the thrust bearing. The new device makes the gearbox more functional and reliable: it also increases driving comfort by reducing noise and vibration from the power unit.

Sophisticated component preparation methods and the use of innovative materials (such as plastic or aluminium) bring a weight reduction of more than two kilos and ensure that the clutch pedal returns more quickly.

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