Vtec: How It Works | Science Garage


Tech just kicked in yo, oh god in the late 90s and early 2000s. The import scene was super hot, and it seemed like civic s2000 and integral GSR drivers. All wanted to make sure everybody knew that their cars had the tech. So what are they even talking about, and what's kicking in when TEC stands for variable valve timing and lift electronic control? It was invented by Honda engineer, into Pakistani in the late 80s, and it's an ingenious way to make an engine, more fuel efficient and more powerful. But. Those are opposites, how does v-tech do that let's brush up on some engine?

Basics about how air gets in and out of the cylinders, so there's a head sitting on top of the engine block and all the air needs to flow through it as the piston goes up and down. It sucks air in and pushes it out through intake and exhaust ports in the head there's. These valves opening and closing those ports like tiny lids constantly popping off and slamming back down again in an engine running at 4000 rpm, the valves.

Open and close 2, 000 times a minute, a spinning camshaft controls the action and timing of the valve there's cam lobes all along the length of the shaft. When we say cams, what we're really talking about are the load as the shaft rotates, the cams bump into things that bump into the valve different engines use different things for that sometimes push rods rocker arms or hydraulic lifters. Some engines use a single camshaft to control all the intake and exhaust valves while others use separate. Camshafts for each set of valves, single cam versus dual, can the exact shape of the cam determines when the valves open, how much they open.

And when they close for lots of complicated reasons that camshaft can totally change the personality of an engine. Imagine we're running an engine, extremely slowly like 10 or 20 revolutions a minute, that's impossible. But at this slow speed, we'd want cam lobes shaped so that just as the piston starts moving downward in the intake, stroke, the intake valve would.

Open then the intake valve would close right as the piston bottoms out when the cylinder is full of air, the compression stroke would happen. And at the end of this, the exhaust valve would open with the piston at bottom dead center, and it would close after the exhaust stroke, but that's, not what happens in an engine because the rpm are in the thousands, the air's got momentum and there are a lot of other things going on that screw with the air coming in and getting out that help the engine run. Leaving valves open longer helps them maximize the intake of fresh air. And the expulsion of exhaust in earlier days, there's, really only one possible cam profile. They threw in a camshaft with a certain size cam lobes on it that got driven by the crankshaft, and that was that. But the cams that make the best valve timing and lift for slow speed, driving and good fuel economy.

Well, they're horrible for making horsepower and going fast specially designed racing cams are big. And they open these valves. Sooner close them later than small cams would we saw in the turbo and nitrous episodes that getting more oxygen into the engine makes more power that little of extra hang time gets in as much air as possible and allows the cylinders to burn more gas and make more power. So big cams work really well at high rpm, but they run like crap at slow speed, the tricks used to shove lots of air and fuel in at high rpm are counterproductive at low rpm that causes messy inconsistent air and fuel delivery. You know that Lopez idle that you hear from cool cars that's, because that car's got big cams fuel efficient engine has small cans. So the valves open just long enough to get adequate power to get the car going that sounds disgusting they're limiting, the amount of air into the cylinder. So they also limit how much gas it needs to burn.

This is all fine at low red. But when the rpm start to rise you're, not able to get a lot of air. So that's, why cars built for good fuel?

Economy are slow, whoa. Most people aren't racing anyway. So carmakers, usually settle on cam sizes somewhere in the middle. You could call that a camp promoter.

This is where TEC kicks in Honda figured out how to run a second cam load profile, basically it's a fancy set of cams that gives you the best of both worlds fuel, efficiency and power from the same engine. If cams determine an engine's personality, TEC has a multiple personality disorder. The Japanese market integral came out with v-tech in 1989. And it first appeared. In the US in 1991 on the Acura NSW, Japan, taxes engines based on displacement. So it made sense in Japan for automakers to think of new ways to make efficient little engines that could still pack horsepower here's how it works. Honda uses dual overhead cams.

And in a TEC engine. Larger cam lobes, sit between the normal-sized ones on the intake, camshaft rocker arms are the middlemen between the cams and the valve as the camshaft rotates. All the cans are bumping up the rocker arms at low and mid-range. Rpm the rockers that pair with the standard cams are the only ones actually moving the valve. The bigger cams rockers aren't connected to any valves, they're, basically, flapping in the wind.

So as you're cruising at 25 in a school zone, the engine runs frugally using the moderate valve timing set by standard can when you hit the freeway on ramp and your right foot starts feeling heavy. You want bigger cams and more horsepower. The car's computer has been keeping tabs on everything when it sees the. Right combination of engine, oil pressure, engine, temperature, engine, speed and throttle position. It decides to grant.

Your wish TEC is gone. The ecu shoots a signal to a solenoid control valve that pushes the hydraulic pin through normal cam's rockers and into the big cams' rocker. This locks those previously independent rockers together.

And when the big cams hit, they push all the rockers down and take over the valve control. Now, the normal cams are the do nothing slackers while the bigger cams start. Opening the intake valve sooner opening them further and closing them later, suddenly you've got more air and more power when you let off the gas a bit.

And the computer decides you don't need the extra grunt anymore, the hydraulic pins retract to let the rockers uncouple. And the engine goes back to running on the small cam and just sipping fuel. And now they have iv tech, which combines multiple cam sizes with continuously, variable valve timing for even more performance. Amazing. I was sleeping down. There, I'm, a bunny guy, dudes guys, dudes, smash, the subscribe button.

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An annual subscription is less than ten dollars a month. I've got that right here in my pants and what's, even better is that the first thousand people to sign up with the link in the description, get the first two months for free so go to skl.sh sciencegarage2 or click on the link in the description, go get skilled. Skillshare the more people who subscribe to donut, the more cool videos we get to do. You can follow me at bidsbarto. You can follow donut media. Furthermore, you want to learn more about getting air in an engine check out this video on turbos. Furthermore, you like TEC check out the up to speed on the s2000 don't, tell my wife about cam, timing.

Dated : 09-May-2022

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