Owners of Ski-Doos know how sweet it is to be able to adjust the shift RPM using their TRA clicker adjusters on the primary clutch. This varies the geometry of the cam arms and rollers so the loading effect of the engine is varied to better match the load of the transmission to the power of the engine, helping to keep the engine spinning at the desired shift RPM.
But, TRA clickers can only do so much. Often times, you want to set the clickers as low as possible to load the engine, get the pipe hot and make all the power you can. Using the TRA clickers isn’t really the ideal way to compensate for changing snow conditions, either. That’s where the ability to vary the helix angle comes into play.
Clutch tuners have long understood the relationship between the primary clutch and the secondary clutch. The primary clutch on the engine controls the engine speed and is RPM sensitive, where the secondary clutch controls the shift ratio and senses the torque from the track. They must both work together, and to some degree each one can be used to “tune” the transmission system. Changing the helix angle changes the systems responsiveness to the load being presented by the track. The secondary must balance the pull from the track with the pull (power) from the engine and let the system operate in the proper ratio, while the primary keeps the engine operating at the right speed, dependent on the throttle position.
So if we can have an adjustable primary component, why not an adjustable secondary component? That’s where Shockwave Performance has made their name, providing sled tuners with easily adjustable helix components so you can adjust the helix ramp angle, instead of replace your helix.
We’ve been using Shockwave adjustable helix components for years on various Yamaha and Arctic Cat models. As the snow gets deeper, or as it gets wetter or as the temperature changes, the load from the track changes and so does the ideal requirement of torque sensing in the secondary. Tuners for years have disassembled their clutches and installed a helix with a different ramp angle to vary both the upshift and backshift characteristics. A steeper helix angle lets the clutches upshift, or open up faster, during acceleration. However, it also makes the system less responsive to an increase in load from the track, so it slows the backshift (downshift). This tends to also reduce the engine RPM.
A flatter or more shallow helix angle slows down the upshift, but lets the system become more responsive to the load from the track, so backshifting is improved. This also tends to increase the engine RPM.
So you come to a lake, hard packed, flat and fast, where a steeper helix angle would benefit your performance. With the Shockwave Adjustable-Ramp Helix, you can quickly dial in a steeper helix angle to let the system upshift harder and faster. Simply open the side panel and turn the dial with an allen wrench. There is no disassembly required. The clutch and the Adjustable Ramp Helix stay assembled in the snowmobile. The allen wrench fits into an adjuster ring. Each full rotation of the adjuster ring is approximately 4 degrees of helix ramp angle change. Thus, each 1/4 rotation is approximately 1 degree. Turn the adjuster ring counter clockwise to let the sytem upshift harder and faster, which will also lower the operating RPM.
Or the next day, it snows six inches of wet heavy snow and your sled isn’t pulling the full shift RPM; the system is being loaded too hard, too fast. Again, open the side panel and turn the adjuster ring clockwise for a flatter helix angle, which will also raise the engine operating RPM. Backshifting response is greatly improved and your engine spins at the right RPM.
New for 2009 is the Shockwave adjustable helix for the Ski-Doo REV XP models fitted with the new QRS secondary clutch. Like the other Shockwave adjustable helixes, you can quickly and easily vary the helix angle in a matter of a minute or two. The ramp angles can be varied by 16 degrees! We really like the adjustability and tenability they provide, and wish that every sled had this feature. Helixes are offered in straight and variable ramp angles, great for trail sleds and a must-have for mountain sleds that experience a greater range of operating conditions within a matter of minutes.
The Shockwave Adjustable Ramp Helix for the Ski-Doo QRS secondary retails for $249. To get yours, contact Shockwave Performance at 763-493-2076 or visit www.shockwaveperformance.com