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How does VTEC Work?


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I know that most of us already know this stuff, but thought this might be a good sticky for all the noobs to read when they join.

 

First a quick video of how vtec works

33AFEA46-D732-479C-A4AB-22E74118BB4A.jpgClick here to see Video

 

 

WHAT DOES THE VTEC SYSTEM IN A HONDA DO?

 

If you have read How Car Engines Work, you know about the valves that let air into the engine and let exhaust out of the engine. You also know about the camshaft that controls the valves. The camshaft uses rotating lobes that push against the valves to open and close them. This animation from How Camshafts Work can help you understand how the camshaft opens and closes the valves:

 

engine-cam.gif

 

It turns out that there is significant relationship between the way the lobes are ground on the camshaft and the way the engine performs in different rpm (rotations per minute) ranges. To understand why this is the case, imagine that we are running an engine extremely slowly -- at just 10 or 20 rpm, so it takes the piston seconds to complete a cycle. It would be impossible to actually run a normal engine this slowly, but imagine that we could. We would want to grind the camshaft so that, just as the piston starts moving downward in the intake stroke, the intake valve would open. The intake valve would close right as the piston bottoms out. Then the exhaust valve would open right as the piston bottoms out at the end of the combustion stroke and would close as the piston completes the exhaust stroke. That would work great for the engine as long as it ran at this very slow speed.

 

When you increase the rpm, however, this configuration for the camshaft does not work well. If the engine is running at 4,000 rpm, the valves are opening and closing 2,000 times every minute, or thirty to fourty times every second. When the intake valve opens right at the top of the intake stroke, it turns out that the piston has a lot of trouble getting the air moving into the cylinder in the short time available (a fraction of a second). Therefore, at higher rpm ranges you want the intake valve to open prior to the intake stroke -- actually back in the exhaust stroke -- so that by the time the piston starts moving downward in the intake stroke, the valve is open and air moves freely into the cylinder during the entire intake stroke. This is something of a simplification, but you get the idea. For maximum engine performance at low engine speeds, the valves need to open and close differently than they do at higher engine speeds. If you put in a good low-speed camshaft, it hurts the engine's performance at high speeds, and if you put in a good high-speed camshaft it hurts the engine's performance at low speeds (and in extreme cases can make it very hard to start the engine!).

 

VTEC (which stands for Variable Valve Timing and Lift Electronic Control) is an electronic and mechanical system in some Honda engines that allows the engine to effectively have multiple camshafts. As the engine moves into different rpm ranges, the engine's computer can activate alternate lobes on the camshaft and change the cam's timing. In this way, the engine gets the best features of low-speed and high-speed camshafts in the same engine. Several of the links below go into the actual mechanics of the VTEC system if you are interested.

 

Several engine manufacturers are experimenting with systems that would allow infinite variability in valve timing. For example, imagine that each valve had a solenoid on it that could open and close the valve under computer control rather than relying on a camshaft. With this type of system, you would get maximum engine performance at every rpm range. Something to look forward to in the future...

 

NOTE: All text below "WHAT DOES THE VTEC SYSTEM IN A HONDA DO?" courtesy of www.howstuffworks.com. Video courtesy of www.streetfire.net

Edited by HungGSR
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And also another explanation

 

WHAT IS VTEC?

 

VTEC is an acronym for Variable valve Timing and lift Electronic Control. It is a mechanism for optimizing air/fuel mixture flow through the engine.

 

An internal combustion engine converts the chemical energy stored in fuel into thermal energy. The increased thermal energy within a cylinder causes the pressure to build. This pressure acts on the pistons and the result is a mechanical force rotating the crankshaft. This mechanical force is measured as crank torque. The ability for the engine to sustain a certain level of crank torque at a certain RPM is measured as Power. Power is the rate at which the engine can do work. This conversion process is not 100% efficient. In fact, only about 30% of the energy stored in the fuel is actually converted into mechanical energy.

 

Physics says that for a given efficiency level, a higher rate of fuel consumption is needed for the engine to generate power. So it becomes obvious that if you want more power, you need to increase the rate of fuel combustion. One way to achive this goal is to have a bigger engine. A bigger engine with larger cylinders will be able to combust more fuel per rotation than a smaller engine. Another method is to pre-presurize the fuel/air mixture and cram it into an existing engine size. Thus even though the cylinder size stays the same, more fuel is combusted per rotation. This second method is referred to as forced induction.

 

Honda chose to explore another method: keep the engine size the same, but turn the engine faster to consume more fuel. Here is an analogy: You want to move foam peanuts from one bucket to another with a cup. You can increase the size of your cup, compress/cram as much peanuts as possible into the cup each time, or you can just move the cup faster. All three methods moves more peanuts. Honda uses the last method. And again, more fuel combusted equals more power generated by the engine.

 

As the engine speed is increased, more air/fuel mixture needs to be "inhaled" and "exhaled" by the engine. Thus to sustain high engine speeds, the intake and exhaust valves needs to open nice and wide. Otherwise you have what is akin to athsma: can't get enough air/fuel due to restrictions.

 

If high speed operation is all we have to worry about, Honda wouldn't need to implement VTEC. Indeed, race engines that operate mostly at high rpms do not utilize any mechanism like VTEC. But street cars used for daily driving spend most of their time with the engine at low RPMs. Valves that open wide for high RPM operation contributes to rough operation and poor fuel economy at low RPMs. These undesirable traits are directly against Honda's design goals.

 

The solution that Honda came up with is the VTEC mechanism: open the valves nice and wide at high RPMs, but open them not as much at low RPMs. So now you have a engine with smooth operation at low RPMs, and high power output at high RPMs.

 

And that is basically what VTEC is. It's nothing magical. The idea has been around for a long time. Honda's VTEC is just a very simple, elegant and efficient implementation that is extremely effective at achiving its design goal. Honda automobiles are the first among modern automobiles to utilize this mechanism in such a large scale of distribution.

 

NOTE: All text below "WHAT IS VTEC?" courtesy of www.howstuffworks.com

Edited by B16Vtec
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I have just one question about VTEC though..

 

I was talking to someone about certain GSR ECU's having a dual-stage VTEC setup? Is this something I should just shrug off or is it something Honda actually put into effect? He mentioned something about stage one engaging at 4500 and another a little after 5500 or 5600?

 

ANyone know?

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I have just one question about VTEC though..

 

I was talking to someone about certain GSR ECU's having a dual-stage VTEC setup? Is this something I should just shrug off or is it something Honda actually put into effect? He mentioned something about stage one engaging at 4500 and another a little after 5500 or 5600?

 

ANyone know?

 

just some extra vids from honda.

 

http://world.honda.com/HDTV/news/2003-4031127a/index.html

http://world.honda.com/HDTV/news/2005-4050705a/

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I have just one question about VTEC though..

 

I was talking to someone about certain GSR ECU's having a dual-stage VTEC setup? Is this something I should just shrug off or is it something Honda actually put into effect? He mentioned something about stage one engaging at 4500 and another a little after 5500 or 5600?

 

ANyone know?

 

A GSR does not have a dual stage VTEC. If you watch that video, you'll see that that's kind of impossible with the way vtec works. He's referring to the butterfly setup in the intake manifold on a GSR. A GSR's VTEC engages at around 4500 rpms. At around 6500 the butterfly setup opens the runners in the intake manifold making the runners longer. It closes them off into shorter runners under 6500 which helps midrange power. It opens them up into longer runners after 6500 which helps higher reving power. That's probably what your friend is confusing with a "dual stage" VTEC setup.

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That's why I originally said around 4500. When I'm driving the rev's go by too fast to tell if it's 4500 or 4600. Either way it's around 4500.

 

Yea I'm running around with a GSR ECU..sucks for me, but I know now for damn sure what it engages at.

Edited by civic cee exx
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That will look sick. I remember seeing one on ebay about 5 years ago with a 98+ integra front end with the type r lip. The thing looked like it came that way it was done so clean.

 

You should put your car back in your sig, just size it down a bit.

 

 

Eh, too many people have told me it looks like a steaming pile o' shat as it is so I figure I'll just wait until it's done to put it up..

 

If I had the money it'd be a JDM Integra front end on the front but..well, can't have everything.

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  • 2 months later...

On the topic of VTEC, anyone know what's up with the new "i-VTEC" on the new Si? It seems like a fad to name things i-whatever nowadays, but I hope there's more to it than that...

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  • 7 months later...
On the topic of VTEC, anyone know what's up with the new "i-VTEC" on the new Si? It seems like a fad to name things i-whatever nowadays, but I hope there's more to it than that...

 

Under low load conditions, only one intake valve opens up. This creates a swirling effect that helps achieve more complete combustion. This basically just helps with the fuel economy.

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Honda reveals the Advanced VTEC engine

 

advancedvtec3lc2.jpg

 

Honda's engineers have been busily figuring out how to make their VTEC engine better, and today the auto giant released the first details about the next-generation powerplant, which they're calling Advanced VTEC. Honda says it plans to have the new engine in a production car within the next three years.

 

Torquier at all speeds, the engine also sets the valves for low lift and early closure at lower load levels, which boosts fuel economy to the tune of 13% over the current 2.4L i-VTEC when the engine is equipped with the proper intake bits. In addition to being punchier and more economical, the engine is cleaner-burning as well, garnering a LEV2-ULEV emissions rating.

 

This is good news. While research and implementation of the various alternative fuel and propulsion solutions is most welcome, there's a lot to be said for the regular, economical four-cylinder gasoline engine. If Honda is on the verge of producing a four with power, more torque (hooray!), better fuel economy and cleaner emissions, the Advanced VTEC is going to be a highly attractive alternative to the alternatives.

 

(Additional photos, press release after the jump)

 

[source: Honda]

 

Honda Advanced VTEC Research Vehicle:

 

advtec01dv8.jpg

advancedvtec1ib8.jpg

advtec02dw4.jpg

 

 

PRESS RELEASE:

Honda Develops Advanced VTEC Engine Combining High Power and Environmental Performance

 

September 25, 2006–Honda Motor Co., Ltd. has further advanced its VTEC (Variable Valve Timing and Lift Electronic Control System) technology with the development of the Advanced VTEC engine, which achieves high performance along with outstanding fuel economy and lower emissions. The new engine combines continuously variable valve lift and timing control with the continuously variable phase control of VTC (Variable Timing Control). Honda plans to release a production vehicle equipped with the new engine within three years.

 

This new system permits optimum control over intake valve lift and phase in response to driving conditions, achieving improved charging efficiency for a significant increase in torque at all engine speeds. Under low to medium load levels, the valves are set for low lift and early closure to reduce pumping losses and improve fuel economy.

 

In combination with optimized intake components, these advances in control technology result in world-class dynamic performance along with approximately 13%* improvement in fuel economy. The new engine is also exceptionally clean, with exhaust emissions that meet both U.S. Environmental Protection Agency LEV2-ULEV regulations and Japanese Ministry of Land, Infrastructure and Transport requirements for Low-Emission Vehicles, with emission levels 75% lower than those required by the 2005 standards (based on Honda calculations).

* Engine only, as compared to production 2.4-liter i-VTEC engine (Honda calculations)

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