Status: Hardware. Date: 2006-2008. Thrust: 6.67 kN (1,499 lbf).
The 4K14 was built specifically for the Rocket Racing League's first X-Racer. The rocket engine was sized for the best compromise between acceleration and endurance for the airframe that was used with the engine.
XCOR's proprietary fuel pump demonstrated the ability to pump from unpressurized wing tanks, which improved air vehicle performance significantly compared to a pressure-fed system. Conventional rocket pumps required relatively high tank pressures (4-7 bar) to force the propellant into the pump. XCOR's piston pump design was able to draw propellant at a much lower inlet pressure, with no fuel tank pressurization system required.
The 4K14 engine used a regulated helium pressurization system for the LOX tank that was very similar to that on the EZ-Rocket.