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How VTEC Works

Old 02-19-2006, 04:42 PM
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Default RE: THIS is how V-TEC works!!

[sm=icon_rofl.gif] lol, that is the best hting i have heard all day
your a ****in retarted dude.
Old 02-20-2006, 10:16 AM
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Old 02-21-2006, 03:13 PM
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^Unnecessary, Lets try and act like adults here, mmmmmkay?
yes mr macky.

"mara-juwanna is bad mmmmmmmbien"
Old 02-27-2006, 03:06 PM
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Old 03-08-2006, 01:57 PM
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Default RE: THIS is how V-TEC works!!

Good video.

Here's some more info from

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.

VTEC, like most things in life, is not for everyone. To decide whether VTEC is for you or not, here are the pros and cons.


The main benefit of VTEC is that the resulting engine is very versatile. The torque curve is very flat: among the flatest of all the engines on the market. Thus where other engines are running out of breath, a VTEC engine maintains a nice and steady output of torque, making the whole RPM range usable for acceleration. So when you are just driving around at a reasonable pace, the car is very smooth and fuel consumption is similar to other engines of the same displacement. When you need more power for passing, all you have to do is down shift and take advantage of the extra power available at the higher RPMs. So you get the smoothness and fuel efficiency of a small economical engine when you drive a low RPMs, and the power output of a much larger engine at high RPMs.

Due to the greater range of usable RPMs, shorter gears can be used. Thus for any given speed or engine RPM, a VTEC engine will allow for a larger ratio multiplier, resulting in more wheel torque. Thus the benefit of the VTEC technology in terms of acceleration improvement also affects low RPM operation.

Since VTEC creates more power without increasing displacement, the engine is likely to be smaller and lighter.


A vehicle achives its greatest acceleration by keeping the engine RPM as close to the HP peak as possible. And for DOHC VTEC engines, this means keeping the needle at some rather lofty RPMs, and more frequent shifts to keep the RPMs up. To some people, including yours truely, this is a desirable trait: lots of driver involvement in the process of extracting excellent performance. To others, especially those accustomed to the Kansas-flat HP curves of muscle cars, the high RPM and frequent shifts become bothersome.

For a good launch off the line, such as at the start of a drag race, a certain amount of tire spin is desired. Muscle cars have torque peaks at low RPMs, and then taper off as the RPM builds. This is perfect for drag racing as the initial torque peak generates the desired tire spin, and then the lower torque at higher RPMs allow the tire to find and maintain grip. But DOHC VTEC's torque curve is very flat, so the initial tire slip is much harder to generate. And once the tire looses traction, the flat torque curve makes it hard for the spinning wheels to find traction. So to properly launch a DOHC VTEC car, the driver must slip the clutch at high RPMs to generate the initial tire spin, and then carefully modulate the clutch and gas to regain drive wheel traction while maintaining maximum acceleration.

Even though Honda's VTEC engines has lived up to the legendary reliability of Honda products, the fact remains that having the VTEC mechanism adds complexity and cost.

US-spec Honda automobiles that have VTEC engines:

Preliminary list, not yet accurate.

# 1996-Current Honda Civic EX coupe and sedan: 1.6L SOHC VTEC I4
# 1999-Current Honda Civic Si coupe: 1.6L DOHC VTEC I4
# 1996-Current Honda Civic HX: 1.6L SOHC VTEC-E I4
# 1998-Current Honda Accord LX/EX I4 coupe and sedan: 2.3L SOHC VTEC I4
# 1998-Current Honda Accord LX/EX V6 coupe and sedan: 3.0L SOHC VTEC V6
# 1997-Current Honda Prelude Base/Type-SH: 2.2L DOHC VTEC I4
# 1993-Current Acura Integra GS-R coupe and sedan: 1.8L DOHC VTEC I4
# 1999-Current Acura TL: 3.2L SOHC VTEC V6
# 2001-Current Acura CL: 3.2L SOHC VTEC V6
# 1991-Current Acura NSX: 3.2L DOHC VTEC V6
Old 03-08-2006, 01:58 PM
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Default RE: THIS is how V-TEC works!!

All the work Honda has done on the VTEC mechanism are combined to make the 3-Stage VTEC system. It is not a rumor, the engine exists: D15B. The engine is used in Honda Civics in Europe and Japan. In short, it combines VTEC-E and SOHC VTEC to get both extraordinarily good RPM fuel economy, and excellent high RPM power. The D15B is a 1.5L engine that is capable of about 54mpg and is rated for about 128HP. There is no other engine that can boast such combination of good fuel economy and power output. To understand how it works, it is recommended that the reader becomes familiar with the DOHC VTEC, SOHC VTEC, and SOHC VTEC-E mechanisms. This article assumes as such.

Looking at Stage 1 above, we see that both intake valve rockers operate independently. And at this low RPM, only one intake valve opens and closes since the other intake valve follows an almost-round cam profile. The almost-round cam profile is designed to open the valve just tall enough to avoid pooling of fuel above the valve. This mechanism is just like the low-RPM operation of the VTEC-E mechanism, resulting in great low-RPM fuel economy.

Stage 2 in the illustration shows the mid-RPM range operation. Starting at about 2500 RPM, the first oil pressure is applied, pusing a pin to lock the two intake valve rocker arms together. Both valves now follow the same low RPM cam profile in their operation. Thus far the operation has just been like a normal VTEC-E mechanism.

In Stage 2 above, the second oil pressure is applied at about 4500 RPM. The second oil pressure pushes another pin through the valve rocker arms and a cam follower that is between the two valve rocker arms. The cam follower operates from the high RPM cam lobe so now both intake valves follow the high RPM cam profile. This is like the high RPM section of an SOHC VTEC engine.

As seen from the power curve graph, each of the three stages has a distinct curve. And by choosing the switch-over points correctly, the optimal portions for the three stages can be combined into one curve. This level of low and high RPM optimization is unavailable from any other mass produced commercial engine.

It seems that combination of VTEC technologies is where the future lies for Honda engines. Already we are seeing this in mass produced US-spec Hondas: the J30A1 V6 used in Honda Accord V6s has a hybrid VTEC-E and SOHC VTEC system, though not a three-stage system like above. In this system, Stage 2 is not implemented. Only Stage 1 and Stage 3 are used: one intake valves open at low RPM, both intake valves open taller and for longer duration at high RPM.
Old 03-09-2006, 05:49 PM
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This is agood link to Honda as well... It explains all the specs on the new motors and transmisions
Old 03-30-2006, 10:12 AM
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Default RE: THIS is how V-TEC works!!

Here is more information on HOW V-TEC WORKS.
Old 06-06-2006, 10:07 PM
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Default RE: THIS is how V-TEC works!!

thanks everyone for the info...its alot easier to understand the vtec with the video
Old 06-07-2006, 08:10 AM
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Default RE: THIS is how V-TEC works!!

LOVE MY VTEC may be the single best invention since gasoline. If you dont have one, you want one

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