How A Basic VTEC System Works

Hi guys, i happen to stumble upon an old Japanese video of the B16A engine with a nice long section showing how a basic VTEC system works for those still new or have little idea of how it actually does. You'll be amazed at how simple it really is.

[After video is finished loading, fast forward to 1:22. The section starts there until 4:20]

[1:22~2:25] Typically, a VTEC system has 3 rocker arm & locking pin assembly and 3 camshaft profiles with the middle one being the performance high-lift profile. During low speed operation (below VTEC switchover point), all the rocker arms move independently according to their own profile thus maximizing low-end torque and improving fuel economy. 

[2:26~4:20] On high speed operation (VTEC switchover point), the VTEC control module operates a hydraulic control valve which increases the oil pressure inside the rocker arm assembly, pushing the locking pins and locks all the 3 rocker arm together now moving on a single high-lift camshaft profile. When returning back to normal low speed operation, oil pressure decreases and the springs in the locking pin assembly pushes back the pins into its original position and unlocks all 3 rocker arm returning it to its own individual cam profile movement.

SOHC VTEC = VTEC mechanism is only on the intake valves

DOHC VTEC = VTEC mechanism on BOTH intake and exhaust valves