I am a member of a university rocketry club and we are in the process of designing a liquid rocket engine. One of the previous propulsion leads did the primary conceptual design of this engine in RPA. Since he graduated, we have switched propellants from N2O/Jet-A to LOX/Jet-A. Because of this, we obviously need to modify some of our design parameters. I am asking here about the characteristic length, L*. This previous lead used an L* value of 2 m. According to this page, the L* for a LOX/RP-1 engine should be 102-127 cm. What would be the consequence of continuing to use the 2 m value?
In my rough understanding of what L* is, I would guess that no major problems will occur, but we may be designing the engine larger than is needed.