2022 Stihl, RB400, comm_handh, , RB 400 DIRT BOSS When you need a power washer that delivers top performance and can stand up to daily use, choose the STIHL RB 400 DIRT BOSS® pressure washer. It features a powerful 196 cc (6.5 hp) engine that can output 2,700 psi of water pressure at 2.7 gallons per minute. It also features the durability STIHL products are known for, with a brass manifold pump design, stainless steel valves, and ceramic-coated pistons.