The enlarged cover also provides more power at low throttle and in the low-midrange, where most riders need it most! It's ideal for trail and hard enduro riders who want smooth power delivery and maximum torque at low RPMs before the power valve opens. The cover works with both stock and aftermarket exhaust systems.
The TBI Oversize Power Valve Cover isn't just for show! It's been meticulously designed and tested to deliver noticeable improvements in the low-midrange. It's most effective between 3000 and 5000 RPM and at low throttle, giving the power delivery a more torquey feel.
Check out the dyno results of our 2024 KTM 300 EXC TBI workshop bike. This bike runs with a TSP medium compression cylinder head and TSP ECU tune. Adding the oversized power valve cover resulted in even more noticeable low-end horsepower and torque gains.
Don't be fooled by the cheap, flashy covers on the market. They are not the same product as the TSP Oversize Powervalve Cover!
How does it work?
At high RPMs, the pressure waves that travel back and forth through the expansion chamber help supercharge the cylinder, filling it with more fresh fuel/air than it would otherwise receive. This supercharging effect and the resulting extra power are often what riders feel when they say a two-stroke engine is "running at full throttle" at higher RPMs.
The downside of this phenomenon is that the same pressure waves that help supercharge the cylinder at high RPMs actually make it harder for fresh charge to enter the cylinder at lower RPMs. This results in a drop in power at low/mid-range RPMs. To counteract this, some power valve systems incorporate a "torque chamber." A torque chamber is a chamber on the side or top of the cylinder that is opened and closed by the action of the power valve. When the power valve is closed or down, the chamber is open to the exhaust gases. When the power valve opens at high RPMs, the chamber closes to the exhaust gases.
At low engine speeds, when the chamber is open, the pressure waves passing through the expansion chamber enter the torque chamber and are partially diverted, losing some of their force in the process. Reducing the force of these waves helps improve cylinder filling with fresh charge. Therefore, the torque chamber provides additional power at lower engine speeds by mitigating the negative effects of the exhaust pipe in this range. By adjusting the volume of the torque chamber, we can further reduce the negative effects of the exhaust pipe at low engine speeds and increase power even more. In this way, the TSP Oversize Powervalve cover contributes to increased power at low engine speeds (approximately 3000–5000 rpm).
To find the ideal chamber volume, we spent months testing various designs on the dynamometer and on the racetrack until we settled on a design that delivered a noticeable improvement in the low-mid-range torque.
To find the ideal chamber volume, we spent months testing various designs on the dynamometer and on the racetrack until we settled on one that provided a noticeable improvement in the low-end torque range.
Fits:
- KTM EXC TBI 250 300 2024-2025
- Husqvarne TE 250 300 2024-2025
- Gas Gas EC 250 300 2024-2025
Not compatible with 2026 models!
