2005 Ski-Doo Racing Handbook, Page 132Get this manual
SECTION 05ENGINE PREPARATION
To the outside of the return spring is red plastic adjustment knob (item 5)Turning the adjustment in or out changes the preload on the return spring which, in turn, will change the RPM at which the RAVE valve opens and closesThe exhaust port height changes total of mm to mm (depending on engine type) from the RAVE valve fully closed to fully open
Operation
The RAVE valve does not allow an engine to make higher peak horsepower than an engine not so equipped, it can make moving the peak higher practical because of its effect on the rest of the power curveItem in following illustration is the power curve of an engine with the RAVE valve held fully open through its entire RPM rangeItem notes the peak power producedThat peak will not change if the exhaust port time of similar engine without RAVE valve was the same (with all other features equal)P1 P2 6