VTEC can use both RPM ranges. At low RPM, the so-called “low-speed cam” allows for better fuel economy and more efficient power consumption. As the RPMs rise, the “high speed cams” take over and allow more fuel and air to be pumped into the combustion chamber, increasing power. The main idea behind VTEC engines from the start is to get more power from a smaller engine. After all, the original VTEC engine was limited to 1.6 liters, but still produced 160 horsepower. This was magic in the late 80s, especially since it wasn’t turbocharged.
Toyota says that three different technologies work together to make VVT-i possible. First, there is the “i” or “intelligent” part. It’s the electronic control unit that makes the whole thing so confusing. Then, the electronic control unit uses a fuel control valve that controls a valve that controls the valves at the top of each cylinder. Compared to Honda’s first iteration of VTEC, Toyota’s system is just as familiar, if not as exciting as VTEC. However, Toyota reported that the system resulted in 6% better fuel economy and more than 10% better performance, thus improving performance.