Difference between revisions of "Alfa Romeo Twin Spark engine"
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Revision as of 17:44, 22 February 2007
| Alfa Romeo TwinSpark engine | |
|---|---|
| Manufacturer: | Alfa Romeo |
| Production: | 1992– |
| Class: | DOHC 2/4-valve I4 |
| Predecessor: | Alfa Romeo Twin Cam |
| Engine: | 1.4 L 1.6 L 1.7 L 1.8 L 2.0 L |
The Alfa Romeo Twin Spark (TS) technology was originally developed by Alfa in the early 1960s in 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.
The 'Twin Spark'
The TS series engines are all '4 cylinder inline' with twin cam (DOHC) shafts, and are developed first with 8 and later with 16 valves. 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 help create a larger flamefront 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. 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 two litre version.
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.