The star-forming efficiency of dense gas is thought to be set within cores by outflow and radiative feedback .
We use magneto-hydrodynamic simulations to investigate the relation between protostellar outflow evolution , turbulence and star formation efficiency .
We model the collapse and evolution of isolated dense cores for \gtrsim 0.5 Myr including the effects of turbulence , radiation transfer , and both radiation and outflow feedback from forming protostars .
We show that outflows drive and maintain turbulence in the core environment even with strong initial fields .
The star-formation efficiency decreases with increasing field strength , and the final efficiencies are 15 - 40 % .
The Stage 0 lifetime , during which the protostellar mass is less than the dense envelope , increases proportionally with the initial magnetic field strength and ranges from \sim 0.1 - 0.4 Myr .
The average accretion rate is well-represented by a tapered turbulent core model , which is a function of the final protostellar mass and is independent of the magnetic field strength .
By tagging material launched in the outflow , we demonstrate that the outflow entrains about 3 times the actual launched gas mass , a ratio that remains roughly constant in time regardless of the initial magnetic field strength .
However , turbulent driving increases for stronger fields since momentum is more efficiently imparted to non-outflow material .
The protostellar outflow momentum is highest during the first 0.1 Myr and declines thereafter by a factor of \gtrsim 10 as the accretion rate diminishes .