Once the engine is started, the propellers spin to create a maximum turbulence in the incoming airstreamWith simple installation steps, you can enjoy going faster and furtherer whilst saving gasoline all at the same timeIt has shipping options to quickly meet every need, including same-day shipping for orders placed as late as 8 p mOnce the engine is started, the propellers spin to create a maximum turbulence in the incoming airstream. With simple installation steps, you can enjoy going faster and furtherer whilst saving gasoline all at the same time. It has shipping options to quickly meet every need, including same-day shipping for orders placed as late as 8 p.m.