Power Valve Cylinder

[Blown 331]

Can someone explain what this is and how it works. I've seen them but I have no idea how it makes more power. Thanks.

[airheadedduner]

If you search it has been talked about a lot. The PV don't make more power, it produces a wider power curve. Most of them are operated by exhaust pressure. There is a slide in the exhuast port that has a spring. The spring can be set up to open earlier or later to produce desired power characteristics. Higher RPM's produce a higher pressure and it moves up a slide in the exhuast port increasing exhaust duration. When there is low pressure the spring pushes the slide down decreasing exhaust duration. Now why PV?? Because with a pv the exhaust duration changes to match RPM via the slide you can port the motor for max power while retaining good low mid. When you port the motor for max power at low RPM's intake charge is lost out the exhaust port. To get back low-mid you can either" A. Lower exhaust duration, decreasing top end power. B. Lower transfer duration, decreasing top end power. C. Run a PV with variable Exhaust duration and have both.

[Chanman420q]

from my understading it "blocks flow" to make better bottom end at lower RPMS but as the RPMS go up, it opens up to make more flow which creates more top end.

[INFANTRY RACING]

basically a short exhaust port make more bottom end while a taller makes more top end. it's basically a valve that opens up to make more top end power as you get higher into the rpm range.