Bwhahahhaha, nah. VarioCam Plus > VTECOriginally Posted by imbosile
I give credit where credit is due.
VarioCam Plus uses a combination of variable valve timing and variable valve lift on the intake side to improve power, torque and fuel consumption across the entire engine-speed range. Essentially, the system offers two engines in one: the first for low-speed and urban use, the second for optimum high-speed performance. Despite the enormous differences between these two states, VarioCam Plus makes a seamless transition using the latest in electronic engine management. The variable valve lift mechanism consists of a two-stage tappet which is operated via an electro-hydraulic switching valve. Each tappet is made up of two main components: a central pin-like element and a cylindrical outer sleeve. When required, these elements can be brought together using a hydraulically actuated shaft. The central pin is actuated by a small-profile lobe on the camshaft, while the outer sleeve remains in continuous contact with two larger profiles on either side. Since there are effectively two cam contours on each intake camshaft, it is possible to apply two different valve-lift curves. The phase angle, or timing, on each of the cams can be advanced or retarded using an electro-hydraulically actuated adjuster.
VarioCam Plus offers a number of benefits when starting the engine from cold. Combustion is improved during the warm-up process, thereby reducing emissions. The system also provides smoother idling while enhancing fuel economy.
Under low throttle loads, VarioCam Plus uses a long positive overlap – i.e., increases the period during which both valves are open simultaneously – as a means of maximising fuel efficiency. Since a relatively high proportion of exhaust gas is present during combustion, there is also a significant reduction in NOx emissions.
In full-throttle mode, the valve gear is adjusted for optimum power and torque. The valve lift is switched to the high cam setting, enabling maximum torque output of 560 Nm on the 911 Turbo from as low as 2,700 rpm. The curve remains flat all the way to 4,600 rpm, covering a significant portion of the engine speed range.
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