Honda's VTEC system allows the engine to have two cam timing profiles, for different RPM ranges.The low-RPM profile maximizes fuel economy while providing enough torque for the engine to idle smoothly. The normal cam profile would limit high-end power, so above a certain RPM, the engine switches to...The high-RPM profile features increased intake and exhaust valve duration and overlap, giving the engine a higher air flow rate, and thus, more power. A performance cam profile that is good at high RPM will cause the engine to idle poorly.An engine with a single, fixed valve profile (not to be confused with a single overhead cam engine) must be designed as a compromise. It won't idle quite as efficiently, it won't have quite as much low-end torque, and it won't have quite as much top-end power.