What is Variable value Timing [VVT]? Here at Scott's Motor Werks we are sometimes asked about VVT. In this article, I'll explain what VVT is, what it does for your mini cooper, and symptoms that your VVT may be demonstrating that require a mechanic's attention.
The variable “valve” timing that we most often see is actually variable “camshaft” timing that improves the low and high-speed torque by advancing or reducing the camshaft timing on single overhead camshaft (SOHC) engine applications. Oppositely, some double-overhead camshaft (DOHC) applications perform those same functions by separately advancing or reducing the intake and exhaust camshafts. Full variable valve timing can be achieved only by using computer-operated solenoids to precisely control the intake and exhaust valve opening and closing actions. Variable camshaft timing on early single-overhead camshaft (SOHC) engines was achieved by using a camshaft “phaser” consisting of a spring-loaded hydraulic piston forcing a beveled drive gear against a similar beveled drive gear mounted on the camshaft.
Variable valve timing can dramatically increase low and high speed engine torque, increase fuel economy and reduce exhaust emissions with tuned intake and exhaust systems. Precise camshaft timing can be achieved by using the Powertrain Control Module (PCM) to apply oil pressure to the piston by pulsing an oil control valve. Since the piston incorporates an orifice to bleed away oil pressure, cam timing can be changed by increasing the pulse width applied to the oil control valve. If the electronics fail, a phaser return spring will push the piston to its default timing position.
VVT requires a good flow of oil to operate the system. When the oil is not changed, or is low, sludge builds up and blocks the small passages. If this happens, we suggest changing the oil and let the detergent in the oil clean the supply passages. Preventing the problem in the first place, by changing the oil as soon as it gets dirty. If the passages are not blocked completely, the detergent may solve the problem. That's why SMW likes to change oil at 5,000 to 6,000 miles.
In closing, it's not important that you know every aspect of VVT because here at Scott's Motor Werks, we have the experience to quickly identify, diagnose, isolate, and repair any of your Mini Cooper servicing needs at a cost often significantly less than the Dealership.
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