Oversized Powervalve Cover for KTM/HQV/GG 250/300 TBI by Two Stroke Performance

How does it work?

How does it work?

At high revs the pressure waves travelling back and forth through the expansion chamber help to supercharge the cylinder, filling it with more fresh fuel/air than it would otherwise receive. This supercharging effect, and the extra power that results, is often what riders feel when they say a 2 stroke is “on the pipe” at higher revs.

The downside of this phenomenon is that the same pressure waves that help to supercharge the cylinder at high revs actually make it harder for fresh charge to enter the cylinder at lower revs. This causes a drop in power at low/mid revs. To combat this some powervalve systems incorporate a ‘Torque Chamber’. A Torque Chamber is a chamber on the side or top of the cylinder which is opened and closed by the action of the powervalve. When the powervalve is closed or down, the chamber is open to the exhaust gasses. When the powervalve opens at high revs the chamber becomes closed to the exhaust gasses.

At low revs, when the chamber is open, the pressure waves travelling through the expansion chamber enter the Torque Chamber and are dissipated somewhat, losing some of their strength. The reduction in the strength of these waves helps to improve the filling of the cylinder with fresh charge. Therefore, the Torque Chamber adds extra power down low by reducing the negative impact of the pipe in this rpm range. By adjusting the volume of the Torque Chamber it can further reduce the negative impact of the pipe at low revs, and increase power even more. This is how the TSP Oversize Powervalve cover helps to increase power at low revs (approx 3000-5000rpm).

In order to find the ideal volume of the chamber TSP spent months on the dyno and track testing various designs until they settled on a design that made a noticeable improvement in low/mid torque.