There has been quite a bit of discussion lately about the classification of the current factory 4-stroke turbo sleds. In the interest of creating some clarity, we can offer the following:
ISR has never classified the current factory 4 stroke turbo charged sleds. There has been a lot of interest in these sleds though, as well as their predecessors including the 1100 turbo from Arctic Cat. In light of these sleds’ popularity, the SSRA created classes for them to compete in a number of seasons ago.
When classifying a sled, it is important to begin with the stock class. With the tuning allowed in stock classes, it was clear that these turbo sleds “should” outrun any other stock sled. Therefore in the interest of fair competition, a new stock class was added, Open Stock. This is the entry class for the current 4-stroke turbo sleds. 2 Stroke sleds can move up to this class as well if they so choose. As in all stock classes, tuning is allowed but OEM components must be used on the turbo sled including all induction and exhaust components.
Moving up to Improved Stock – if a class was needed to be created for a stock class sled, then one needed to be created for these sleds that are improved as well. Therefore, the Open Improved Stock class was added. Obviously the technology of a turbo charged 4 stroke sled is different from that of a 2 stroke sled, so the intake and exhaust modifications for the turbo sleds were looked at. The modifications that were settled on were mufflers, air intake (as long as it remains under-hood), charge tubes (as long as they are OEM diameter), and wastegate and blow-off valves. It is important to note that the engine components, turbo, and exhaust header must all remain stock OEM. It is also important to note that just like in other Improved Stock classes, engine stutter and launch control devices are not allowed.
Moving up to additional classes – Although it has a minimum track requirement, the Mountain Improved Stock class is a step up from the regular Improved Stock classes. This is because more modifications are allowed that can reduce weight and improve performance. For this reason, a sled that is Open Improved Stock qualified can move up to Mountain Improved if it meets the track requirements. If the 4 stroke turbo sled has modifications that do not qualify it for Open Improved, it will compete in Mountain Open, Open Mod 1000, or Outlaw, depending on the nature of the modifications.
We hope this brings some clarity to the discussion and we encourage anyone with further questions about a particular sled configuration to contact Dale for further information.