- Variator
A variator is a device that can change its parameters, or can change parameters of other devices. Often a variator is a mechanical
power transmission device that can change itsgear ratio continuously (rather than in steps)."See also:"
continuously variable transmission Alfa Romeo/FIAT Variator
Variator is the name for the
Alfa Romeo andFIAT variable valve timing device. It is a cylindrical chamber which contains a pressure chamber and piston along with helical gears. It is situated on the inlet camshaft of theTwinSpark generation enngines. Engine oil pressure, moves the internal piston which rotates slightly due to the helical gears and advances the inlet valve timing by 25 degrees. Oil flow to the variator is controlled by asolenoid . When engine speed reaches a certain speed, normally 1500-200rpm in theAlfa Twinspark application, thesolenoid energises, causing pressurised oil to be directed through the inlet camshaft into the variator. The inlet camshaft position is advanced 25 degrees, thus increasing valve overlap. It remains in this advanced state until about 5000rpm when the solenoid switches off, and the variator piston returns the valve timing to it's natural state. It increases the engine's mid-range flexibility and reduces emissions. Exact changeover points are dependant on version. TheFiat Stilo with the 1.8l or 2.4l engines andAlfa Romeo 1.6l, 1.8l and 2.0l use a variator with the only exception being theAlfa 147 Junior. This has a 105BHP engine, not the 120BHP version.If the petrol engine sounds like a diesel briefly after starting, it means that the variator is worn and should be replaced. When significantly worn, the noise remains until about 1500rpm. Variators are best replaced at the same time as the timing belt. They will only cause noise, and not fail completely.
The variable valve timing was first commercially used in the
Alfa Romeo Alfetta Gold Cloverleaf in 1985. The next engine to employ a variator was the75 Twinspark of 1988. These engines had 8 valve heads on the classic all alloy block and not the 1990sFiat /Alfa cast iron block engine which is the subject here.
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