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46-605: In the current Alfa Romeo world the "Twin Spark" name usually refers to the dual ignition engines installed in Alfa Romeo cars. The 8-valve engine was fitted initially to the Alfa Romeo 75 but also the 164 and 155 . The 16-valve engines appeared in the 145 , 146 , 155, 156 , 147 , 166 , Alfa Romeo GTV & Spider and Alfa Romeo GT models. The TS series are all twin cam 4-cylinder inline engines. The original 8-valve engine

92-454: A single point of failure in mechanical terms, that could cause both ignition systems to cease working. A simple form of partial dual ignition on some amateur-built aircraft uses a single spark plug, but duplicates the coil and pick-up for better redundancy than traditional single ignition. A further form of partial dual ignition (such as on the Honda VT500 ) is for each cylinder to have

138-404: A diesel type rattle from the top of the engine, which appears at startup and gradually lasts for longer. It is therefore advisable to get the variator changed regardless of its apparent condition at the 36,000 mile (60,000 km) cambelt replacement. The variator problem is not often seen in the earlier 8V Twin Spark version, as these use a different type of cam timing variator system, this is also

184-438: A four-cylinder four-stroke engine (with a single plug per cylinder) requires only 2 coils alternately firing every 180° of crankshaft rotation, each coil firing every 360° crank rotation to fire all four cylinders. In the 16 Valve Twin Spark 4 coils are required by the eight plugs, so production economy was unlikely to be a factor in the adoption of a wasted spark system. On the later CF3 (2001 on Euro 3 emissions standard) 16v TS

230-456: A heavier cast-iron block engine, with an alloy head, and the camshafts were belt driven. The Twin Spark name comes from the fact that there are two spark plugs per cylinder. It was cast iron for its higher beam strength, less complexity and hence lower production costs. When new, these engines were notable for their high efficiency as demonstrated by the BMEP (brake mean effective pressures) exerted upon

276-467: A replacement interval of 100,000 kilometres (62,000 mi). The 16 Valve engine features individual 'coil over plug' ignition where the timing of the ignition is controlled directly by the Bosch engine management system, with each coil firing two spark plugs simultaneously. On the earlier CF1 and CF2 16 valve engines each coil fired the plug below it and (via a short plug lead) a plug in the other cylinder that

322-605: A single HT coil which sends the current to one plug and completes the circuit via the second plug, rather than via the earth. This system requires a voltage sufficient to jump both plug gaps, but an advantage is that if one plug fouls, the fouled plug may burn itself clean while the engine continues running. Wankel engines have such an elongated combustion chamber that even non-aero wankel engines may adopt dual ignition to promote better combustion. The MidWest AE series Wankel aero-engine has twin plugs per chamber, but these are placed side-by-side, not sequentially, so their main purpose

368-465: A trumpet radius on the same diameter inlet Variable valve timing gave the Twin Spark engine very good performance for its cubic capacity, but it is one of the weaker areas of the 16-valve engine. The original variator that controls the cam timing is prone to wear or jam, although replacement part carries a different part number and has improved reliability. Symptoms are a slight loss of performance and

414-503: A variator system with two variators, one for each camshaft. Like the Alfa Romeo system, these are electrically-controlled hydraulic units, mounted in the camshaft's timing belt pulley. These systems are fitted to the Volkswagen VR5 and VR6 engines , and also to the W8 and W12 engines . The multiple- bank W engines have four variators in total, one for each camshaft. The Volkswagen variator

460-470: Is advanced 25 degrees, thus increasing valve overlap . It remains in this advanced state until about 5000 rpm when the solenoid switches off, and the variator piston returns the valve timing to its natural state. The variable timing increases the engine's mid-range flexibility and reduces emissions. Exact changeover points depend on version. It is notable that this relatively early system only has two settings: unchanged and fully advanced. Volkswagen use

506-424: Is effectively a velocity stack which reflects a positive pressure wave back down the inlet runner to maximise cylinder filling with fuel/air mix. The rpm band over which the pressure wave arrives at the open inlet valves and is able to assist in the cylinder filling is set by the length of the runner and is a relatively narrow. Swapping between runners of differing length broadens the rpm band over which benefits of

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552-415: Is ideally located in the centre of the cylinder, as is common in virtually all multi-valve configuration engines. In order to accommodate a second spark plug in the 4-valve combustion chamber, a smaller diameter spark plug is located the very edge of the combustion chamber between an inlet and an exhaust valve. The location of the additional plug means that its impact on maximum performance is marginal. However

598-526: Is no room for a centrally positioned spark plug due to 2-valve design which uses rather large 44 mm diameter inlet valve on the 2.0 engine. On the newer models using the 8V engine the system uses the popular wasted spark system as well. (as also used in Ford EDIS), combining one coil for 2 plugs on opposite phase sister cylinders like 1-4, 2-3 on 4 cylinder engine. On the Alfa 16V Twin Spark engines one spark plug

644-480: Is referred to as a 'fluted variator', owing to the shape of the hydraulic components. Unlike the Alfa Romeo system with its helical splines and indirect actuation, the Volkswagen system has a direct rotational action. The internal components of the variator resemble a paddle wheel inside a loose casing, so that it is free to move a few degrees from side to side. By applying hydraulic pressure on one side of these paddles,

690-424: Is serviced by two coils. In case of a coil failure one of two plugs would still work. Ignition systems that fire a plug in a cylinder on its exhaust stroke are referred to as a wasted spark ignition system; as the spark ignites nothing and so is 'wasted'. Wasted spark systems are generally used as a production economy as half the number of coils are required (which consequently have to fire twice as many times), e.g.

736-546: Is to give redundancy rather than improved combustion. Richard W. Dilworth of the Electo-Motive Corporation devised a system, using four spark plugs and one carburettor per cylinder, in order to burn "distillate" fuel in train car engines. Because such heavy, but cheap, fuel was hard to ignite, a quadruple system of ignition was used in order to burn fuel roughly equivalent to kerosene or home heating fuel. By using this distillate fuel, that cost as little as one-fifth

782-619: The Nissan NAPS-Z engine, with Ford introducing it on the 1989 Ford Ranger and 1991 Ford Mustang four-cylinder models. Several modern Mercedes-Benz engines also have two spark plugs per cylinder, such as the M112 and M113 engines. Some motorcycles, such as the Honda VT500 and the Ducati Multistrada , also have dual ignition. The 2012 Ducati Multistrada was upgraded with "twin-plug cylinder heads for smoother, more efficient combustion",

828-582: The World War I years, when such engines as the Hispano-Suiza 8 and Mercedes D.III , and even rotary engines as the later Gnome Monosoupape model 9N 160 hp (119 kW) versions featured twin spark plugs per cylinder. The Hewland AE75 , an inline three cylinder aero-engine created for the ARV Super2 , had three ignition circuits, each circuit serving a plug in two different cylinders. If just one of

874-701: The ability to advance and retard ignition timing in individual cylinders, which would be impossible in the CF1 and CF2 configurations as each cylinder is serviced by two coils, but could be used in the CF3 setup. The engines also incorporate two other devices to enhance the performance under operation, the Camshaft Phase Variator and the Variable Intake Length Control (or Modular Inlet Manifold in Alfaspeak) on

920-484: The case for later 16v versions used in the Alfa Romeo 156 and the 147 where the weak variator was addressed. applications: Applications: Dual ignition Dual Ignition is a system for spark-ignition engines, whereby critical ignition components, such as spark plugs and magnetos , are duplicated. Dual ignition is most commonly employed on aero engines , and is sometimes found on cars and motorcycles. Dual ignition provides two advantages: redundancy in

966-527: The change contributing to a 5% increase in torque and a 10% improvement in fuel consumption. Early BMW R1100S bikes had a single spark plug per cylinder, but after 2003 they were upgraded to dual ignition to meet emission law requirements. Dual ignition in aero-engines should enable the aircraft to continue to fly safely after an ignition system failure. Operation of aero engines on one magneto (rather than both) typically results in an rpm drop of around 75 rpm. Its existence on aviation powerplants dates back to

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1012-504: The closing of the exhaust valves, the valve overlap (the period both inlet and exhaust valves are simultaneously open) is also increased at this mode. This promotes the scavenging effect of the exiting exhaust which causes a partial vacuum in the cylinder to further assist in filling the cylinder with a fresh charge. Also this increased overlap, may cause part of the exhaust gases to re-enter in this way make it function like internal EGR. As with similar inlet cam phasing systems like BMW VANOS

1058-499: The control unit sets the "open" phase: cam advanced by 25°, inlet casing long ducts (Only 1.8/2.0 TS). At the maximum power speed the control unit sets the "closed" phase: cam in normal position, inlet box short ducts. At idle speed the control unit sets the "closed" phase: cam in normal position and inlet box short ducts. In the other engine operating conditions, the control unit selects the most suitable configuration to optimise performance - consumption - emissions. During overrunning,

1104-413: The device is termed variatore di fase . The Alfa Romeo Twin Spark engine , introduced in the 1987 Alfa Romeo 75 , also uses variable valve timing. The Alfa system varies the phase (not the duration) of the cam timing and operates on the inlet camshaft. Alfa Romeo's variator is a cylindrical chamber that contains a pressure chamber and piston along with helical splines. Engine oil pressure, moves

1150-588: The earlier internals of the variator. The same variator system is also used in many Fiat / Lancia engines like one used in Lancia Kappa 5-cylinder engine, some Fiat Bravo / Fiat Marea engines, Fiat Barchetta , Fiat Coupe , Fiat Stilo etc. models. The Alfa Romeo Modular Inlet Manifold is a variable intake system fitted to the later CF2 1.8 and 2.0 litre Twin Spark engines. It operates by switching between two separate air intake runners of different lengths (one pair for each cylinder) to either shorten or lengthen

1196-507: The engine is able to idle smoothly in very lean conditions (up to 18:1 AFR), this suggests the addition plug is here to improve combustion efficiency under light loads. The next generation Alfa fours, the JTS engines lost the second plugs gained direct injection and increased performance. The TS 16V engines, 1.6, 1.8 and 2.0, all use a 10 mm diameter and a 14 mm diameter long life platinum electrode spark plug per cylinder. The spark plugs have

1242-429: The engine will have at least two ignition circuits, such as duplicate magnetos or ignition coils . Dual ignition promotes engine efficiency by initiating twin flame fronts, giving faster and more complete burning and thereby increasing power. Although a dual ignition system is a method of achieving optimum combustion and better fuel consumption, it remains rare in cars and motorcycles because of difficulties in siting

1288-439: The event of in-flight failure of one ignition system; and more efficient burning of the fuel-air mixture within the combustion chamber. In aircraft and gasoline-powered fire fighting equipment, redundancy is the prime consideration, but in other vehicles the main targets are efficient combustion and meeting emission law requirements. A dual ignition system will typically provide that each cylinder has twin spark plugs , and that

1334-493: The four coils fire both spark plugs in one cylinder (so not 1 & 4 and 2 & 3 as pairs), and may not be a wasted spark system. The potential benefits of each coil being associated with one cylinder being: halving the firing frequency - the coil is only required to fire every 720° crankshaft rotation rather than every 360° crankshaft rotation. This would double coil saturation time, reducing coil load and improving spark quality at high rpm. Some Bosch engine management system have

1380-428: The gases can begin only after the closure of the inlet valves so by varying the intake valve closure moment (with the variator) the effective compression ratio can be reduced in not-advanced position. This has benefits as a way to reduce the effective compression ratio but still keep the expansion ratio as before so to lower the compression phase mechanical losses. When the intake valve is also opened earlier in relation to

1426-437: The inlet ducts of the box are always short. " The advancing of the inlet camshaft opens and closes the intake valves earlier in the inlet cycle. This allows the filling of the cylinders with air/fuel mix to begin and end earlier when in advanced position thus starting to compress the mix earlier. Or the compression phase to begin later (when in not advanced cam state) by delaying the intake valve closure. The actual compression of

Alfa Romeo Twin Spark engine - Misplaced Pages Continue

1472-415: The intake tube). There is much discussion on about improving performance by removing the trumpet or 'de-coning' as it is often referred to, as the trumpet is thought by some to restrict air flow due to its small inlet cross-section. While "de-coning" results improvement in inlet cross-section any benefit is likely to be off set by the 'pinch effect' of an unradiused inlet, which is 0.6 - 0.5 the efficiency of

1518-479: The internal piston which rotates slightly due to the helical splines and advances the inlet valve timing by 25 degrees. Oil flow to the variator is controlled by a solenoid valve . When engine speed reaches a certain speed, normally 1500-2000 rpm in the Twin Spark application, the solenoid energises, causing pressurised oil to be directed through the inlet camshaft into the variator. The inlet camshaft position

1564-616: The later (plastic cam cover) 1.8- and 2.0-litre versions. Where both these variable systems are deployed they are controlled in tandem by the Bosch Motronic Engine Management ECU in response to rpm, load, and throttle position. According to Fiat Auto S.p.A. DTE electronic service documentation for the 156 Twin Spark (1.8/2.0): " To optimise the quantity of air drawn into the engine the control unit checks: inlet timing on two angle positions (and) geometry of inlet ducts at two lengths (only 1.8/2.0 TS). At maximum torque speed

1610-421: The path from the end of the intake runner (within the plenum) to the inlet valves. The system is manifold vacuum-assisted servo-operated, and controlled directly by the Bosch engine management system, as described above. Tuned-length inlet runners operate by using the harmonics created by within the inlet tract/runner by the opening and closing of the inlet valves and flow of gas during the inlet cycle. Each runner

1656-435: The phasing is returned to the retarded state at higher rpm to improve power and efficiency as inlet gas dynamics change with rpm. The short inlet ducts being tuned to the higher frequency and thus shorter inlet duct pressure wave. On the 16V engines the camshaft variator is used to enhance the performance/emissions but also might be the source to the common 'diesel noise' problem often seen on high mileage used models which used

1702-416: The piston crowns. The two sparks plugs on the 8V Alfa Twin Spark engines fire at the same time and are symmetrically placed around the vertical line passing through the intake and exhaust valve centers. The flame front travels less distance which allows less ignition advance to be used. Also, leaner mixtures can also be tolerated for better fuel economy. The 8V engine also has 8 identical spark plugs. There

1748-547: The price of gasoline before the Great Depression , a railroad could save substantially on fuel costs. However, this patented ignition system saw little commercial use. Variator (variable valve timing) Variable valve timing (VVT) is a system for varying the valve opening of an internal combustion engine . This allows the engine to deliver high power, but also to work tractably and efficiently at low power. There are many systems for VVT, which involve changing either

1794-415: The relative timing, duration or opening of the engine's inlet and exhaust valves. One of the first practical VVT systems used a variator to change the phase of the camshaft and valves. This simple system cannot change the duration of the valve opening, or their lift. Later VVT systems, such as the helical camshaft or the movable fulcrum systems, could change these factors too. Despite this limitation,

1840-449: The second plug within the cylinder head (thus, many dual ignition systems found on production automobiles typically were of a two valve design rather than a four valve). The Nash Ambassador for 1932-1948 used twin sparkplugs on the straight eight engine, while later Alfa Romeo Twin Spark cars use dual ignition, as do Honda cars with the i-DSI series engines , and Chrysler's Modern Hemi engine . In 1980 Nissan installed twin sparkplugs on

1886-481: The three circuits failed, all three cylinders still received sparks, and even if two circuits were to fail, the remaining circuit would keep the engine running on two cylinders. While true dual ignition uses completely separate and redundant systems, some certified engines, such as the Lycoming O-320-H2AD use a single engine magneto drive-shaft turning two separate magnetos. Whilst saving weight, this creates

Alfa Romeo Twin Spark engine - Misplaced Pages Continue

1932-496: The tuned inlet runners are achieved, leading to a flatter torque curve and consequently more power across the rev range. In addition air-flow within the stock intake tubing between the throttle plate and airbox has also been maximised. This includes an 'inlet trumpet' at the end of the intake pipe within the airbox (often referred to as the "cone" by Alfisti) which is designed to improve airflow and fuel metering by reducing turbulence, (and may reflect positive pressure waves back down

1978-425: The variator is a relatively simple device to add to an existing engine and so they remain in service today. As the benefit of the variator relies on changing the relative timing between inlet and exhaust, variator systems are only applied to double overhead camshaft engines. A variator system that moved a single camshaft for both inlet and exhaust would be possible, but would have no performance benefit. Alfa Romeo

2024-413: Was 360° crankshaft rotation out of phase (i.e. one coil would fire a spark plug in the cylinder nearing the top of the compression stroke, and also the a spark plug in the cylinder nearing the top of the exhaust stroke (in a 4-cylinder 4-stroke engine with a 180° crank pistons 1 & 4 and pistons 2 & 3 rise and fall as pairs). So in this configuration each coil services two spark plugs and each cylinder

2070-512: Was derived from Alfa's Twin Cam family, and featured a light alloy (silicon enhanced aluminium alloy) block + head, wet-cooled iron cylinder liners , and the camshafts were driven by a single duplex timing chain. So, similar design to the earlier and famous Alfa Romeo Twin Cam engines , but with narrower valve angle and double ignition on this model. The later 16-valve engines were part of Fiat's " Pratola Serra " (B family) modular engine series, and had

2116-558: Was the first manufacturer to use a variable valve timing system in production cars (US Patent 4,231,330). The 1980 Alfa Romeo Spider 2.0 L had a mechanical VVT system in SPICA fuel injected cars sold in the US. Later this was also used in the 1983 Alfetta 2.0 Quadrifoglio Oro models as well as other cars. The technique derives from work carried in the 1970s by Alfa Romeo engineer Giampaolo Garcea and in Italian

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