Alfa Romeo Twin Spark engine
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| Alfa Romeo TwinSpark engine | |
|---|---|
| Manufacturer | Alfa Romeo |
| Production | 1986– |
| Predecessor | Alfa Romeo Twin Cam |
| Class | DOHC 2/4-valve I4 |
| Engine | 1.4 L 1.6 L 1.7 L 1.8 L 2.0 L |
Alfa Romeo Twin Spark (TS) technology was used first time in Alfa Romeo racing cars in 1923 . In the early 1960s it was used their race cars (GTA, TZ) to enable it to achieve a higher power output from its engines. And in the early and middle 1980s, Alfa Romeo incorporated this technology into their road cars to enhance their performance and to comply with stricter emission controls.
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[edit] The 'Twin Spark'
Twin Spark name refers usually engines made after 1986 when the 164 Twin Spark was introduced. The TS series engines are all '4 cylinder inline' with twin cam (DOHC) shafts, and are developed first with 8 valves (an all alloy wet-liner engine, chain driven) and later with 16 valves (a modern iron block engine with alloy head, belt driven). All cars featuring the Twin Spark engines since the Alfa Romeo 155 (which originally also came with the 8V unit) use the 16 valve models over the 8V ones. The Twin Spark name comes from the fact that there are two spark plugs per cylinder. The two sparks on the early Alfa twin spark engines fired on the power stroke to help create a larger flame front ensuring less unburnt fuel in the exhaust as well as a higher thermodynamic efficiency. The 8V units have 8 identical spark plugs, while the 16V ones have a larger and a smaller plug in each cylinder. On the later 16v TS engines the smaller plug ignites on the exhaust stroke to reduce emissions. The common TS 16V engines, 1.6, 1.8 and 2.0, all use a 10 mm diameter and a 14 mm diameter plug per cylinder.
The engines also incorporate two devices to improve the performance under normal operation, the Camshaft Phase Variator and the air intake Variable Inlet Control on the 1.8 and 2.0 litre versions.
[edit] Variable Inlet Control
The Variable Inlet Control causes the air intake (plenum) to shorten its path from the intake trumpet to the valve bores, again when the engine reaches a pre-defined RPM. This works on the principle that the air intake length is a tuned pipe that when operating at its ideal frequency-in tune with the valves, will allow a smooth and even air flow, and will assist with filling the cylinders efficiently. This works in a similar method to the tuned exhaust system on all modern cars, where the exhaust system creates back pressure to pull spent gasses from the cylinder bores. Modifying this tuned system in any way and failing to re-tune it will create performance drops..........
The notable effect that these two devices have is that the engine will surge powerfully forward on hitting the ~4300 rpm mark, right up to the RPM limiter.
[edit] Other Applications
The 4 cylinder T series Toyota engine utilized Alfa Romeo's Twin spark design for its World Rally Championship engine, the 4t-gte. It was also applied in the consumer version of that engine, the 3t-gte, and is a relatively sought after design in semi-classic Toyota tuning circles.
The 1.9 litre 6 cylinder inline Porsche engine set in the racing-only 911R (of which twenty were produced) utilized the twin spark design in a souped up engine from the 911T. Production ran from 1967 to 1969 and the change to twin spark helped boost the engine's output from 130hp to 210.
