Gear Motor PT. SARANA TEKNIK Terlengkap

MOTOVARIO Variator is the name for the Alfa Romeo and FIAT variable valve timing (VVT) device. Alfa Romeo first applied VVT in 1980 to the long-established Twin Cam engine used in the Alfa Romeo Spider.[1] It is best known for its use throughout the Twin Spark engine introduced with the Alfa 75. The technique derives from work carried in the 1970s by Ing. Giampaolo Garcea.[1] In Italian the device is termed variatore de fase.[1] Unlike systems that vary the duration of valve opening, the Alfa system varies the phase relationship between a camshaft and crankshaft (i.e. piston position). The Alfa system, on their twin cam engine, is only applied to the inlet camshaft, the exhaust camshaft being unaffected. It is a cylindrical chamber which contains a pressure chamber and piston along with helical splines. Engine oil pressure, moves the internal piston which rotates slightly due to the helical splines and advances the inlet valve timing by 25 degrees. Oil flow to the variator is controlled by a solenoid. When engine speed reaches a certain speed, normally 1500-2000rpm in the Alfa Twinspark application, the solenoid 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 its natural state. It increases the engine's mid-range flexibility and reduces emissions. Exact changeover points depend on version. It is notable that this relatively early system only has two settings: unchanged and fully advanced. The Fiat Stilo with the 1.8l or 2.4l engines and Alfa Romeo 1.6l, 1.8l and 2.0l use a variator with the only exception being the Alfa Romeo 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 splines are worn and should be replaced. This was a regular occurrence for the 16 valve Twin Spark. When worn, the noise remains until about 1500rpm - the variator is usually quieter when in the advanced position. 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.[citation needed] The next engine to employ a variator was the 75 Twinspark of 1988. These engines had 8 valve heads on the classic all alloy block and not the 1990s Fiat/Alfa cast iron block engine which is the subject here