If you're a car enthusiast, you've probably heard the term "VTEC" before, but you might not know what it means. If you don't, here's an explainer.
VTEC is a type of variable valve-timing system developed and used by Honda. It stands for Variable Valve Timing & Lift Electronic Control. Like most other variable-valve timing systems, VTEC varies oil pressure to shift between different cam profiles. At higher engine speeds, the cam profile allows greater valve lift, which allows more air into the cylinder. This helps generate more horsepower. Since its introduction in the late 1980s, VTEC has been used in many of Honda's best performance cars including the NSX, Integra Type R, S2000, and Civic Type R.
But the way VTEC goes about switching cam profiles is totally distinct. Most variable valve-timing systems use increased oil pressure to shift the timing of the camshaft, opening the valves earlier; VTEC uses an entirely different set of cams at high RPMs.
Explaining the process with words alone doesn't do it justice. Jason Fenske at Engineering Explained put together a video showing exactly how VTEC works, using real Honda engines and visual diagrams. If you want to know what happens inside the engine, definitely give this clip a watch.
As Fenske explains, VTEC-equipped engines have two rocker arms with their own low-profile cams for each cylinder, and a central rocker arm with its own high-profile cam, which is unused at low RPMs. As engine speeds rise, a piston inside the rockers is pressurized with oil, locking all three cams together to increase valve lift. This is where that signature "VTEC kicking in" sound comes from.
Now next time you "get into VTEC" while driving your Honda, you'll know exactly what's happening inside your engine.