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Originally Posted by bmussatti
I don't think it is just the VarioCam. Since the VarioCam varies the timing of the intake camshafts to optimize performance at any engine speed or load. The camshaft angle is continuously varied by the twin rotary valve vane adjusters.
On the 987, at about 4500 RMP, the torque curve is at about optimum- 191 lb.ft. (Max being 199)
And for the 987S, at about 4500 RPM, the torque curve maxes out at 236 lb.ft.
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Hi,
VarioCam's job is to increase/decrease
Valve Overlap to maximize Torque and Power. In the past, selecting a Cam was always a compromize between these two.
By Advancing/Retarding the Valve timing, you can increase Torque, Power, and lessen Emmisions. Retarding the V Timing in the Low-Mid Ranges increases Torque, while Advancing the V Timing at Idle and Low RPM Range increases Power and reduces HC Emissions.
There are 2 versions of VarioCam on the Boxster. Only on the Latter version is the adjustment
Continuously Variable.
The 1st version - '97-'02 used an Electric Solenoid which Advances the Intake Cam 13°, the limit of this system is that it is either ON or OFF at a pre-set RPM controlled by the DME.
The 2nd version - '03-'06 eliminates the Solenoids and uses an Oil-filled Stator. This allows for infinitly variable V Timing within a 40° Range. This is where much of the HP/Torque gains are had over previous MY. Also, a Synchronizing chain between pairs of Cams is eliminated probably eliminating a 1-2 HP Parasitic Loss.
Happy Motoring!... Jim'99
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