Alfa Romeo Twin Spark engine
|Alfa Romeo TwinSpark engine|
|Class:||DOHC 2/4-valve I4|
|Predecessor:||Alfa Romeo Twin Cam|
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'
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 Alfa twin spark engines fire one after the other on the power stroke causing higher compression as the flame front travels across the combustion chamber. The second spark firs in the extra compressed mix, ensuring a cleaner burn and 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 there are 4 independent 8-ampere coils, connected to plugs; 1a and 4a, 1b and 4b, 2a and 3a, 2b and 3b. This arrangement facilitates the separate firing of the spark plugs in each combustion chamber, and also saves parts by utilising a "wasted spark" system, where - between the exhaust and inlet stroke of each pistons "partner" - a useless spark occurs, this may improve emissions very slightly, but the intention is to reduce cost. The common TS 16V engines, 1.6, 1.8 and 2.0, all use a 10 mm diameter and a 14 mm diameter platinum electrode spark 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.
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.
|1954–1994||Twin Cam||1290, 1570, 1750, 1779, 1962|
|1992–present||TwinSpark||1.4, 1.6, 1.7, 1.8, 2.0|
|1971–1995||Flat-4||1186, 1286, 1350, 1490, 1712|
|1979–2006||V6||2.0, 2.5, 3.0, 3.2|
|2006–present||GM based V6||3.2|
2 valve Twin Spark engines
- 1.7 L 1749 cc 84 kW (115 PS) @6000 rpm, 146 N·m (108 ft·lbf) @3500 rpm
- 1.8 L 1773 cc 98 kW (129 PS) @6000 rpm, 165 N·m (122 ft·lbf) @5000 rpm
- 2.0 L 1962 cc 109 kW (148 PS)@5800 rpm, 186 N·m (137 ft·lbf) @3000 rpm
- 2.0 L 1995 cc 104 kW (143 PS) @6000 rpm, 187 N·m (138 ft·lbf) @5000 rpm (cat.)
4 valve Twin Spark engines
- 1.4 L 1370 cc 76 kW (103 PS) 6300 rpm, 124 N·m (91 ft·lbf) @4600 rpm
- 1.6 L 1598 cc 77-88 kW (105-120 PS) @5600-6200 rpm, 140-146 N·m (103-108 ft·lbf) @4200-4500 rpm
- 1.8 L 1747 cc 103-106 kW (140-144 PS) @6500 rpm, 163-169 N·m (120-125 ft·lbf) @3500-3900 rpm
- 2.0 L 1970 cc 110-114 kW (150-155 PS) @6400 rpm, 181-187 N·m (133-138 ft·lbf) @3500-3800 rpm
- Alfa Romeo 145
- Alfa Romeo 146
- Alfa Romeo 155
- Alfa Romeo 164
- Alfa Romeo GTV (Type 916)
- Alfa Romeo Spider (Type 916)
- Alfa Romeo 156
- Alfa Romeo 147
- Alfa Romeo 166