Variator (variable valve timing)

[1] There are many systems for VVT, which involve changing either the relative timing, duration or opening of the engine's inlet and exhaust valves.

Despite this limitation, the variator is a relatively simple device to add to an existing engine and so they remain in service today.

The 1980 Alfa Romeo Spider 2.0 L had a mechanical VVT system in SPICA fuel injected cars sold in the US.

The technique derives from work carried in the 1970s by Alfa Romeo engineer Giampaolo Garcea and in Italian the device is termed variatore di fase.

Engine oil pressure, moves the internal piston which rotates slightly due to the helical splines and advances the inlet valve timing by 25 degrees.

Like the Alfa Romeo system, these are electrically-controlled hydraulic units, mounted in the camshaft's timing belt pulley.