VTEC or Variable Valve Timing and Lift Electronic Control is a type of engine apparatus engineered by Honda. The Japanese auto maker has been including this type of engine in several of its models for the last few years. This type of engine offers enhanced performance through innovative camshaft design. Other manufacturers have also begun to offer their own versions of this technology.
In most vehicles, a camshaft spins a cam, or an outsized piece, that lifts valves according to its positioning. In single or double overhead cam engines, the camshaft may be driven by a chain or gear. When the camshaft spins, the cams, also called cam lobes, push the valves open at just the right instant of the "piston stroke" to help facilitate the right air/fuel mix for proper engine combustion. In other types of engines, called pushrod engines, the camshaft is also belt driven, but it is located inside the engine block. Long pushrods are displaced by the cam lobes and move the "rockers" that open and close the valves.
In a VTEC engine, the design uses multiple “camshaft profiles” to provide greater variance on how valves are controlled. The cam setup in a conventional engine uses designations of TDC (top dead center) and BDC (bottom dead center) to provide the right timing for opening and closing the valves to get the right fuel/air mix. In a VTEC engine, the valves are either held open for longer, or opened and closed later.
VTEC engines also take advantage of an "automation" not found in conventional engine models. An electronic signal can implement either a high RPM cam or a different cam for low RPM and fuel efficiency. This adds to engine versatility and performance.
The dual cam design of this type of engine is controlled by the ECU or engine computer. The ECU uses factors like oil pressure, engine temperature, vehicle speed, engine speed and throttle position to figure out when it’s time to switch from one cam to the other. The system also evaluates engine load, which has an effect on the “switch point” for the VTEC system.
Buyers of newer Honda models can get an engine equipped with i-VTEC or “intelligent-VTEC”, where there is even greater variability for switching between the two camshaft profiles. I-VTEC represents part of a general revolution in auto design, where more and more of the core processes of the engine are taken over by computerized parts and sensors. The general consensus is that these dynamic changes provide better fuel efficiency and overall performance. However, these changes can make it difficult for a traditional mechanic to fully troubleshoot and maintain a newer vehicle.
Buyers of the newest cars on the market can evaluate the benefit of a specific Honda engine by taking a look at manufacturer specs. Honda posts these on the web site, with details on miles per gallon, horsepower and more for each engine it ships. There's also a lot more on the Honda site for helping customers to choose the appropriate Honda technology for their ride.