Used by Takaaki Shimo and other drivers, OS Speed have their new .21 engine here called the 21XZ-R. Featuring all new crankcase internals, as well as new crankshaft and piston liner, they have created a motor with more torque and better fuel economy.
The fuel economy is proving an advantage as Shimo is inside the top 4, running only one stop. The engine also sports a lightweight cooling head which is lower than its predecessor, coming down over the crankcase. Its available from next month.