How VTEC works: Why Hondas have that sudden burst of speed

Honda developed its Variable Valve Timing & Lift Electronic Control (VTEC) technology to make its cars quicker, more efficient, and more enjoyable to drive overall. The technology’s frequent appearance in Fast and Furious movies has turned it into a widely known meme. Many have heard the phrase “VTEC just kicked in, yo!” but few know how it works. Here’s what you need to know about the system.

Engine basics

Gasoline-powered engines require four things to generate horsepower: Air, fuel, compression, and spark. For the purposes of understanding the VTEC system, we’ll focus mainly on the air part of that equation. A part of the engine known as the camshaft controls when and how much the valves open and close, and therefore how much air goes into the engine. On this camshaft are raised points known as lobes, which, as the camshaft rotates, will push the valves open and then closed via rocker arms. Larger lobes will open the valves further than smaller ones.

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Unless you’re familiar with engine internals, you might have gotten a bit lost in that last paragraph, so let’s define both what camshafts and valves are, and give you a crash course on how an engine works.

In an engine, the camshaft is a long rod that normally sits above the cylinder and the piston, and that operates the valves which plug up both an intake channel and an exhaust channel. One rotation opens the intake channel, allowing fuel and air into your engine’s cylinders. Your spark plug discharges, allowing the fuel inside to combust, and another rotation opens the exhaust channel as the intake channel is closed, pushing out the exhaust gasses.

During this process, the pistons move up and down in the cylinders. Engines can use either one or two camshafts, and they’re driven either by a timing chain or a timing belt.

The below video explains what we just talked about (start at about 49 seconds).

Quite a few variables control how an engine produces the power needed to make a car move. More air into the engine means more power, since the combustion process is accelerated, but too much of it isn’t necessarily a good thing. The process of opening and closing the valves that we just described works well at low revolutions per minute (rpm), but the valves open and close so quickly as the engine builds up speed that performance ultimately starts suffering.

How VTEC is different

Honda’s Australian division published the video below to explain how its VTEC technology works. We suggest you watch it before reading the rest, because it will help our explanation make a whole lot more sense.

In a traditional engine, the camshaft opens and closes the valves, and its lobes are all the same size. In Honda’s VTEC engine, the camshaft has two different lobe sizes: Two standard-sized outer lobes and a larger center lobe. At lower rpm, only the outer lobes are controlling the valves. As the engine begins to spin more quickly, the center lobe takes over and the valves open sooner and closer later, which results in a sudden burst of speed and better performance.

This change also causes the engine to have a sudden change in pitch — that’s “VTEC kicking in.”

Does VTEC really do anything?

Yes and no; it depends on how you drive. Honda cars equipped with VTEC technology tend to be more efficient across a wider rpm range than many comparable vehicles, and they’re a lot of fun to drive in the right conditions, but most motorists won’t notice their VTEC kicking in. It’s active when the engine is operating relatively high in the rev range, and you rarely get there in normal driving conditions, especially if your car has an automatic transmission. But, if you’re the shift-your-own-gears type and you like twisty roads, VTEC makes a noticeable difference.

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