phaser would be locked at low rpm then unlocked as engine rpm approached 2500 rpm 12 then locked again when the engine reached 2800 rpm 15 as engine speed increases the phaser would once again be unlocked above a selected rpm of approximately 4500 rpm where the minimum 11 and maximum 10 tension curves begin to diverge 0028 fig2 a and 2 b show resonance effects in another very different example engine u2014 a four cylinder engine equipped with a vct system this engine shows effects which require the method of the invention to choose the opposite at high rpm of the v6 in this example it can be seen that the minimum 23 and maximum 22 tension lines with the phaser unlocked fig2 b diverge widely as the engine rpm exceeds about 5000 rpm 24 with the phaser locked fig2 a however the minimum 21 and maximum 20 torques remain much closer together as the rpm increases thus in the engine of fig2 a and 2 b the phaser would be unlocked at lower rpm then locked as the rpm passes a selected point above approximately 5000 rpm 24 where the resonance effects change thus it can be seen that the method of the invention is performed by 1 recording the timing drive forces over a range of engine rpm both with the phaser locked and with the phaser unlocked 2 analyzing the recorded timing drive forces to identify resonance effects 3 while the engine is operating choosing the locked or unlocked status of the phaser at a given rpm to minimize effects of resonance identified in step 2 accordingly it is to be understood that the embodiments of the invention herein described.