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

It’s what Honda enthusiasts point to as one of the brand’s main advantages, but to others it’s become somewhat of a pop culture enigma — and a meme to boot. It’s called VTEC – short for Variable valve Timing and lift Electronic Control, and it’s what gives you that sudden surge of acceleration moments after stepping on the gas in a Honda.

But why and how does this happen, and what about it makes the Honda VTEC engine different from others? In this explainer, we hope to give you a better understanding of the process so you can 1) educate yourself and 2) impress all of your friends.

Engine basics

For a combustion engine to work, it requires four things: air, fuel, compression, and spark. For the purposes of understanding the VTEC system, we’ll focus here mainly on the air part of that equation. A part of the engine known as the camshaft controls how much the valves open and then 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. Larger lobes will open the valves further than smaller ones.

How VTEC Works: Why Hondas have that sudden burst of speed
Bradley Iger/Digital Trends

Unless you’re familiar with engine internals, you might have gotten a bit lost in that last paragraph, so lets define both what a camshaft and a valve is, and give you a crash course on how an engine works.

In your engine, the camshaft is a long rod that sits above your cylinder and piston that operates the valves which plug up both an intake (for fuel) channel and a exhaust channel. One rotation opens the intake channel, allowing fuel and air into your engine’s cylinder. 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 any exhaust.

During this process, the piston moves up and down within the cylinder to both help draw in air, and push it out.

Engines can use either a single or dual camshaft to operate these valves. A single camshaft design operates both the intake and exhaust valves using the same camshaft, while others may employ separate ones. Regardless, as we mentioned before the size of these camshafts control how far those valves may open and close, and whether one or two, those lobes will all be the same size.

The below video explains what we just talked about a little better (start about 0:49 in).

As you can see, there is quite a bit of variables that control how your engine produces the power to make your car move. More air into the engine means more power, since the combustion process is accelerated. But too much isn’t necessarily a good thing.

The simplistic valve opening and closing process we described earlier works well throughout lower RPMs, as there is sufficient time for air to enter the engine to facilitate the combustion process. However, engines are designed to be efficient, so those camshaft lobes must be a size that balances both efficiency and power. At higher RPMs, your valves are opening and closing so quickly that it’s difficult for this process to occur, and thus your performance suffers considerably.

How VTEC is different

While a bit dated, this video from Honda’s Australian arm does a very good job of explaining VTEC in a visual way, which we think is better to understanding the process overall. Watch this before reading the rest, it will help our explanation make a whole lot more sense:

In the traditional engine, the camshaft controls valve opening and closing, and its lobes are all the same size. In Honda’s VTEC engine, as you saw in the video the camshaft has two different types of lobe sizes: two standard-sized outer lobes and a larger center lobe. This center lobe is attached to separate center rocker arms from the outer lobes, so at lower RPMs only the outer lobes are controlling the valves.

However, when the engine’s RPMs are suddenly increased, oil pressure causes the rocker arms attached to the center lobe to lock together, and allow the valves to open wider, resulting in increased performance and a sudden burst of speed as the engine suddenly is able to produce more power.

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

Does VTEC really do anything?

Haters will tell you absolutely not — thus why it’s become somewhat of a point of derision. However there are legitimate reasons for it. Hondas with VTEC engines are much more efficient across a wider RPM range than most other vehicles, and arguably are much more fun to drive for those of us who value pick up and go. But for a large majority of us, you’ll likely not “ride VTEC” in everyday driving.

That’s because the RPM threshold for VTEC is quite high — for most 4,500 rpm or so. In normal driving, you’ll be lucky to consistently stay above 3,000, maybe 3,500 rpm tops, especially with in automatic transmissions. But should you need performance suddenly, say during a spirited drive or to pass the Sunday driver ahead of you — you sure will enjoy those few seconds of VTEC bliss.

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