[alfa] some VVT observations

["Hans@ ItalianMotorWorks" <hans@xxxxxxxxxxxx>]

First, all VVTs are hydraulically operated. It requires oil under pressure to
advance the intake cam, and the oil comes from the #6 cam journal.
The early VVTs were centrifugally actuated, by a little anchor shaped weight
on the front of the sprocket, whereas from 1984 on up they were actuated by a
solenoid sitting on the front of the cam cover, and controlled by the ECU.
USA spec VVTs advance the cam 10 degrees, Euro spec VVTs advance 16 degrees.
Having the intake cam retarded at idle makes for a smoother, cleaner idle
because it reduces overlap and that makes it run cleaner at low rpm.
Above 1650 rpm the cam advances, we get more overlap and more power.
I've had some performance cams modified to use the early VVT to make the cams
more streetable, and the idle improvement is noticeable.
IAP sells a mild performance cam that uses the VVT.
end of sermon.
Hans
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