Originally posted by ContourZetec:
VCT doesn't give you HP it is strictly an EMISSION CONTROL unit.


This is not entirely correct. The VCT enables Ford to use longer duration cams, still meet emissions requirments and provide a stable idle.

(ZX2 with VCT) Intake: 214 deg @0.050, 0.367" lift Exhaust: 211-2 deg @0.050, 0.338" lift
(Focus w/o VCT) Intake: 206 deg @0.050, 0.353: lift Exhaust: 205 deg @0.050, 0.343" lift

The exhaust VCT advances the exhaust cam 30 crank deg under PCM control. Advancing the exhaust cam reduces the intake-exhaust overlap by the same amount. At low rpm this results in a better idle and more torque using longer duration cams. The European tuners have learned how to use VCT to their advantage with longer duration cams.

In the Focus engine, Ford used a better intake and exhaust manifold and better flowing cat to compensate for the shorter duration cams while meeting emissions.

For a high rpm race engine that does not have to meet emissions or streetabilty requirements you are correct. VCT does not provide any performance benefits.

However, if you need to meet emissions and want a stable idle, then VCT does allow the use of higher performance cams. People have reported passing emissions tests using cams with durations greater than 220 deg and lifts above 0.390, if the VCT and catalyst were operating.

Having VCT on both intake and exhaust cams (similar to the BMW dual VANOS system) would be ideal, but we have to make do with what we have.

People have talked about a adding a centrifugal mechanism to retard the intake cam with increasing rpm (similar to what Mercedes did on the twin cam 6 over 30 years ago) in conjuction with the exhaust VCT. Due to the complexity no one has acted on this idea. It might be possible to add a centrifugal mechanism to an adjustable cam gear.