Better understanding variable valve timing

A relatively modern innovation in the world of automotive engineering (though it’s been around the block for more than a few decades now), variable valve timing gives automotive engineers the opportunity to improve power, performance, and fuel efficiency. It can do these all at the exact same time! It can produce impressive results across the board.

Almost all major automobile manufacturers take advantage of variable valve timing in some way or another, with Honda and Ferrari leading the charge interestingly enough. Both of these legendary automobile manufacturers take advantage of variable valve timing in a different way than the other. They produce different results and desired outcomes, but each of them use technology built on the back of the same science, the same reasoning, and the same logic.

If you’d like to learn a little bit more about how variable valve timing impacts your automotive performance, and why it is such a big part of modern automobiles, you’ll want to pay close attention to all of the details we have for you below.

vvt vanos

What exactly is variable valve timing, anyway?

Internal combustion engines rely on a number of moving parts (each of which are connected to the camshaft and play off of one another). All of these parts need to be working in concert to produce the energy and force necessary to propel a multi-thousand pound vehicle down the road at 60 miles an hour or more.

Valves in each cylinder are going to contain the internal “explosions” that make internal combustion possible in the first place. They need to be appropriately timed to open and close at just the right moment to supply air for the fuel/air mixture that makes combustion possible as well as allowing force from the explosion to escape and be transferred to the drivetrain.

It is a lot of moving parts that all need to be perfectly timed for optimal efficiency. This is why so many automobile manufacturers out there have tried to perfect variable valve timing so that everything works as smoothly as can be.

vtec variable timing

The Honda approach to variable valve timing

Honda has been leveraging variable valve timing technology for decades now. Some would say that they have perfected the technology. That is, at least as far as consumer focused vehicles are concerned.

Sure, they use similar technology in the supercars and race cars that they produce as well, but the bulk of the vehicles that they produce use the “civilian” variable valve timing system known as VTEC.

Standing for Variable Valve Timing and Lift Electronic Control (talk about a mouthful), VTEC engine are designed to leverage multiple camshafts all working in concert with one another to produce impressive performance, speed, torque, and power without decreasing fuel efficiency across the board. Honestly, the engineering behind VTEC engines is nothing short of spectacular. This is why Honda vehicles are able to enjoy such a sterling silver reputation all over the world.

These VTEC engines have extra intake cams that run off of their own rockers (following the cam) that operate independently. At low speed, this rocker isn’t connected to any of the valves in the engine while at high speed a piston locks into the extra rocker and intake valves help supply more fuel to increase efficiency and performance.


The Ferrari approach to variable valve timing

Manufacturers of some of the most impressive (and legendary) supercars on the planet, Ferrari engineers are always looking for ways to squeeze even just a bit more power and performance out of their vehicles to give them the competitive edge they are known for.

The variable valve technology used in all Ferrari vehicles manufactured today leverage three-dimensional profile cuts along the length of each cam lobe. On one end of the lobe the three-dimensional profile cut is a lot less aggressive, but it becomes more and more aggressive as you move to the opposite end.

This allows these cam lobes to match up like gloves at both low and high speeds, adjusting how the valve timing syncs up depend entirely upon how quickly you’re moving and the demands of the engine through the camshafts that are hooked up. It’s an ingenious approach perfect for supercars, though it may not be quite as ideally suited to Honda Civic-esque vehicles!

variable valve timing

Why was variable valve timing invented?

Variable valve timing is the result of a lot of vehicle testing. The part that opens and closes the valves is called a camshaft. A camshaft has ground lobes on it that rotate. You can only grind one cam profile for each valve. After decades of testing gasoline engines, it became apparent that one cam profile was not ideal for all RPMs. There is one optimum cam profile for low RPM fuel efficiency. There is a different Cam profile that is best for high RPM power output. For an engine to be efficient while also making a lot of power and torque, it needs more than one cam profile. That’s why variable valve timing was invented.

In actuality, most variable valve setups have the same cam lobe profile. The way that they vary the opening and closing of the valves is to change the point of the crank shaft rotation where the cams start to open the valves. The cam profile itself remains the same throughout the RPM range. It just starts earlier or later in relation to the crank and the ignition timing.

Filed in: Gasoline Engines
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