The microwave power and the critical current of spin torque oscillator (STO) devices with a built-in hard axis polarizer have been studied. This design allows for an external-field-free STO. The time domain oscillation signals give direct evidence of higher output from the hard axis polarizer STO, which agrees with spectroscopic results. The hard axis polarizer STO generates a higher power because of the larger slope of the magnetoresistance-angle curve at the lowest energy potential. Furthermore, the hard axis polarizer STO shows a low critical current indicating the large spin torque effect when two magnetic layers are in the 90 configuration.