The four engines equipping the 164 in its various versions, incorporate state-of-the-art design solutions based on engineering principles tailored to suit each engine's special nature. These solutions were worked out by Alfa Romeo through a concentrated effort aimed at boosting power and torque performance without losing sight of the different displacements and the specific operating cycles and fuel feed systems of the individual engine models. The target in view, in the development of the new technical features, was not limited to the attainment of higher top speeds and brilliant acceleration and pick-up.
Every facet of the engines' design, fuelling, ignition, production and quality control was optimised with these objectives:
Having decided to position the engines transversely, special studies were devoted to a new drive unit system for a more effective connection to the body shell that would minimise the noise and vibration transmitted to the inside of the car, avoid jerkiness in the drive line, and at the same time reduce to a minimum the jolts produced by engine shake over rough road surfaces.
To this end, all the Alfa 164's versions have been fitted with special reaction-rod-assisted hydraulically-damped engine mounts.
This six-cylinder power pack mounted on the most powerful and fastest version of the 164 represents a further evolution of the engine used on the Alfa 75~3.O V6 America and Milano models. Its salient characteristics are:
Total displacement is 2,959 cc, obtained with a bore x stroke of 93 mm x 72.6 mm. Unit cylinder capacity is about 493 cc. The compression ratio is 9.5 : 1.
Maximum power output, delivered at 5,600 rpm, is 192 bhp DIN. A torque peak of 25 mkg DIN is reached at 3,000 rpm, but 85% of it is already available at 1,000 rpm and over 90% at 2,000 rpm, confirming the outstanding flexibility of this power pack.
Torque evenness, obtained by distributing total displacement over six cylinders, helps a great deal to enhance very quiet, vibration-free running.
The 3 litre V6 developed for the Alfa 1 64 features a Vee configuration with the cylinder banks set at 600 angles giving a highly compact design. Thanks to the latter characteristic, transverse mounting did not entail any particular difficulty but helped accommodate redesigned intake and exhaust manifolds and enabled auxiliary parts to be efficiently rearranged.
The engine block (with pressed-in "wet" liners), cylinder heads and oil sump are all made of aluminium-silicon alloy. This makes for reduced engine weight, high mechanical strength and best possible dissipation of unwanted heat.
The 60o angle selected for the two cylinder banks allows ideal evenly spaced ignition at 120o intervals. For this reason, the particularly short and sturdy crankshaft, featuring 100% balancing with extra counterweights applied to the flywheel and front pulley, is subjected to a minimum amount of torsional vibration and is effectively protected against the 1st and 2nd order vibration periods produced by the pistons' reciprocating motion.
The innovative timing system used on the Alfa 164 3.0 V6 engine is the outcome of extensive development work, to attain unprecedented efficiency and a highly compact configuration.
The camshafts, one for each row of cylinders, are driven by a toothed belt with built-in-hydraulic tensioner. The intake valves, featuring improved inertia thanks to their larger diameter, are operated directly, while the exhaust valves, sodium-filled for faster cooling in keeping with Alfa Romeo's engine tradition, are operated indirectly via short, rigid rods and rocker arms. Valves are arranged at an included angle of 46o, to provide the part-spherical design of the combustion chambers and hence efficiency, which also benefits from a reduced bore/stroke ratio; the engine powering the 164 3.0 V6 in fact, is "over-square"with a 0.78 bore/stroke ratio.
Both functions, on the Alfa 1643.6 V6 engine, are governed by the Bosch Motronic integral electronic system in its latest, most refined vesion, the ML 4.1.
The system co-ordinates the operation of the multi-point injection system and that of the ignition system by means ofan electronic control box which receives and processes a continuous stream of data on engine revs, air flow rate and temperature, engine temperature and the position of the accelerator-controlled butterfly valve.
The ML 4.1 works by means of actuators which adjust the duration of fuel flow through the injectors as a function of the foregoing parameters and modify spark advance accordingly.
Moreover, the system adjusts idling speed, cuts off fuel feed when the accelerator pedal is released, and meters the enrichment of the air-fuel mixture for cold starting and accelerating purposes; if necessary, it also prevents the upper rev limit from being exceeded.
This 4-cylinder electronic injection unit-derived as we have seen from a Lancia engine-powers the more powerful and faster of the two 2-litre petrol-engined versions of the Alfa 164. It features highly advanced engineering solutions, including:
A total displacement of 1,995 cc is obtained with an 84 x 90 mm bore x stroke. The compression ratio is 8 : 1.
Peak power output, 1 75 bhp DIN, is produced at 5,250 rpm. A high torque of 27 mkg DIN is made available at only 2,500 rpm, a figure that emphasizes the flexibility of this power unit. With the overboost, torque can be raised to 29 mkg at 2,500 rpm.
This engine, developed for the Alfa 164 TB, is a four-cylinder unit mounted transversely, tilted forward, with the exhaust components facing forward for more effective cooling since this layout means airflow hits the turbocharger directly.
A cast iron engine block is mated to an aluminium alloy cylinder head.
In order to control oil temperature under the most demanding operating conditions, the lubrication system has been provided with its own cooling radiator.
The Alfa 164 TB features a Bosch LE-2 Jetronic multi-point electronic injection System with a special fuel feed over-run cut-off device.
The turbocharging system employs the most sophisticated solutions made available by state-oFthe-art technology. The Garret T 3/50 turbocompressor, water-cooled to eliminate carburising its oil film bearing features a built-in waste-gate valve.
Downstream from the turbocharger, an intercooler lowers the temperature of compressed air by 50-70oC, thus leading to an increase in its specific mass and final compression pressure, which in turn results in higher power, greater reliability and improved specific consumption values.
Thanks to this turbo installation an impressive power output of 175 bhp DIN has been achieved on an 8-to-I compression ratio: very few 2-litre units can match this figure.
A further contribution to the brilliant performance ratings of the Alfa 164 TB engines is made by the overboost, a device that steps in when the driver floors the accelerator. A sizeable increase in torque is produced for either a limited or an unrestricted period of time depending on engine revs.
This device, derived from aeronautics technology, acts on the waste-gaste and produces a temporary increase in the amount of exhaust gas delivered to the turbine resulting in higher relative boost pressure up to a maximum of 0.95 bar (3.8 psi). Through a pneumatic circuit, the same Microplex control box that is responsible for the operation of the ignition system controls overboost function and turns it off if necessary, depending on operating conditions, after a predetermined time interval.
At low revs, the overboost is mostly used when overtaking, and this is why it cuts out automatically. At higher revving speeds the overboost will enhance full power delivery and will stay on as long as the driver exercises maximum pressure on the accelerator. Thanks to a sophisticated knock sensor connected to the Microplex unit, the waste-gate is automatically restored to normal operation if knocking starts. The driver is shown when the engine is on overboost by means of a telltale on the dashboard.
A static advance digital type ignition system has been selected for the petrol turbo. This means sparks are produced at high and constant voltage level, for proper plug operation even under the most difficult conditions. The entire sequence is governed by a Marelli Microplex microprocessor.
Spark advance, based on sophisticated studies allowing for over four thousand different configurations, is determined by processing the data received from sensors of crankshaft speed and intake pressure.
The knock sensor built into the Microplex system has been specially designed to detect instantaneously the vibration produced in the cylinder head by incipient knocking. It cuts in to produce first of all an immediate decrease in boost and then, if necessary, a reduction in spark advance.
The combined use of the LE-2 Jetronic electronic injection and Microplex mapped ignition has heightened the efficiency of the Alfa 164 TB engine while ensuring excellent fuel economy
This power unit, equipping the naturally aspirated 2-litre used on the Alfa 164, is a direcLdeflvative of the engine fitted on the 2.0 Twin Spark version of the Alfa 75, a recent addition to the Alfa car range. It includes a number of exclusive engineering solutions resulting in superior power output and exceptional peak torque for this cylinder capacity. Its main characterstics are:
Cylinder capacity amounts to 1,962 cc thanks to an 84 mm bore and 88.5 mm stroke.
Compressiosn ratio is 1 0 : 1.
Maximum power output at 5,800 rpm is a remarkable 148 bhp DIN, while maximum torque, of 19 mkg DIN, is reached at 4,000 rpm. The shape of the torque curve has been perfected to make available fully 16 mkg when revving speed reaches 2,000 rpm and 18 mkg as early as 3,000 rpm, thus making the engine's performance much more responsive.
The engine used on the Alfa 164 T. Spark is a four-in-line cylinder unit whose weight has been considerably reduced with all aluminium-alloy engine block, cylinder head, oil sump and tappet cover.
Eight counterweights ensure optimal balancing of the high strength nitrided steel crankshaft.
The pressed-in cast iron cylinder liners feature wet mounting for more effective heat dissipation.
The twin overhead cams, driven by a double chain, act directly on the valves set in a tight Vee configuration (46o).
The timing of the valve train is not fixed as in most present day engines, but can be adjusted by a patented device conceived and produced by Alfa Romeo, the timing variator.
This is an electro-hydraulic actuator keyed onto the gear that drives the camshaft acting on the intake valves. This actuator enables the camshaft to be shifted into two different angular positions and to modify the intake valve opening durations. Its operation is controlled by the electronic control box of the integrated ignition and fuel injection system.
Valve timing actuator logic is predetermined so that overlap - i.e. that fraction of the engine's operating cycle when both the exhaust and the intake valves are open simultaneously - is shorter at low revs and with lighter loads, and longer at higher engine speeds when extra power is required.
This offers the following advantages:
The, ignition system on the Twin spark is a digital system with static spark advance and no moving parts subject to wear. It is mapped by the integrated digital electronic control box which also handles fuel injection and valve timing. It features two plugs per cylinder.
This innovative solution, also entailing a special configuration of the hemispherical combustion chambers and piston heads, ensures a fast, wide flame front when the air-fuel mixture is ignited, and therefore less ignition advance, enabling, moreover, relatively lean mixtures to be used.
As a result, the adoption of twin spark ignition yields:
The Alfa 164 T. Spark power plant is equipped with the ML 4.1 Bosch Motronic multi-point injection system, controlled by the same microprocessor which governs the twin spark ignition and variable valve timing Systems.
The excellent volumetric efficiency of the Twin Spark engine is also enhanced by the special straight section individual intake manifolding that cuts down losses and fully exploits intake resonance for better mid-range torque.
Having all thermodynamic cycle components under the wings of a single electronic control unit means that the power plant used on the Alfa 1 64 T. Spark can guarantee-in addition to outstanding torque and power figures-regular, smooth running at all speeds regardless of load. Moreover, this engine features particularly attractive specific fuel economy compared with rival naturally aspirated units in the same displacement class (with savings of up to 20-25%).
The diesel-engined version of the Alfa 1 64 has a totally new power plant under its bonnet: a 4-cylinder turbo specially designed and manufactured on the basis of the Alfa-Romeo VM system principles.
A good number of innovative characteristics have been packed into the Alfa Romeo Turbo, not to be found on the majority of car diesel engines in current production. Such as:
Maximum power output, 117 bhp DIN, is produced at 4,200 rpm. Peak torque, 26 mkg, becomes available at 2,500 rpm, but engine flexibility is so good that 85% of this value is available at 1 500 rpm.
The cast iron block of the diesel turbo is distinguished by a special tunnel-shaped layout with partition walls in between the cylinders.
The crankshaft, with four counterweights, !s not supported by main bearings held in place by conventionel bridge type bearing caps in the same material as the block. Its bearings are located within light alloy discs which on starting expand twice as much as cast iron and are therefore gripped by the holes in the "tunnel". This structural solution ensures maximum engine sturdiness combined with a significant dampening in crankshaft vibration and mechanical noise.
The light alloy cylinder heads are partitioned off from each other and hence are free to expand in any direction without putting too much strain on the block. In actual practice, this eliminates the risk of deformation brought about by "thermal stresses," and prolongs engine life despite the load effects to which such a powerful unit is exposed.
Moreover, maintenance is greatly simplified.
In the same effort to minimise harmful distortion, a special mounting system has been devised for the cylinder liners which are "suspended" inside the block and are thus free to expand without risk of deformation. The liners are "wet," that is, in direct contact with the coolant. Thanks to this new mounting system, it has been possible to make the cylinders of centrifuged cast iron, a material particularly resistant to heat, wear and pressure.
The partition between engine block and cylinder liners, in which the latter have been re-designed for optimal thickness and dimensions, improves mechanical strength and cooling. Moreover, optimal strain-free piston-liner mating has been achieved, so as to prevent penetration of lubricant into the combustion chamber (the cause of high oil consumption), and at the same time minimise burnt gas leakage into the sump and lubricant contamination.
Piston configuration was aimed at maximum mechanical strength and to this end Alfa's engineers fashioned trapezoidal conrod small ends and gudgeon pins. Moreover, at high engine speeds, the pistons are cooled by directed high pressure oil jets from the engine block.
The camshaft, which acts on the valves by means of rods and rocker arms, is driven by a single plane gear train at the engine's front; this train also includes the injection pump gear. Such a solution ensures the maximum degree of angular precision necessary for the combustion cycle to remain optimal over time.
In order to cut down noise levels, the middle gear of the train is split in two, with each half-width gear torsionally sprung against its neighbouring half in order to automatically take up play. Moreover,the gear train is enclosed inside an extra thick plate double-skin cover plus an inner layer of soundproofing material.
The pre-combustion chamber indirect injection power plant used on the Alfa 164 TD is equipped with a Bosch injection pump working in conjunction with automatic devices which govern fuel flow, starting spark advance, and engine speed.
The rapid acting glow plugs in the combustion chamber come with a special device that enables them to stay on for some time after engine starting (after-heating) until optimal warm-up conditions have been reached, resulting in faster engine stabilisation and greatly reduced smoke emission.
Diesel oil heating is provided by a thermostat controlled device which ensures prompt take off in very cold weather and makes for trouble-free operation by keeping the filter cartridge free from waxing.
Turbocharging is handled b a KKK turbocom ressor su lied from an intercooler which reduces the temperature of compressed air by 50-60oC before this is fed into the cylinders.
Besides improving the engine's thermodynamic efficiency, by supplying cooled and therefore denser air to boost power and torque figures, the intercooler also helps to reduce thermomechanical stresses, thereby enhancing engine durability.
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