[CleanGSR]

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
http://thumbs.streetfire.net/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:

http://static.howstuffworks.com/gif/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

This post has been edited by HungGSR: 02 April 2008 - 07:55 AM

[CleanGSR]

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

This post has been edited by B16Vtec: 24 February 2006 - 10:07 AM

[SolLesHonda]

Great post, and great job actually quoting where you got it.


TL or VR, Can you sticky this thread?

[blackdelsol]

yea I've read that too. very good info for newbs

[Ben.]

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?

[InfinitePrelude]

civic cee exx, on Feb 25 2006, 12:17 AM, said:

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.c...127a/index.html
http://world.honda.c.../2005-4050705a/

[VR17]

SolLesHonda, on Feb 24 2006, 08:44 AM, said:

Great post, and great job actually quoting where you got it.
TL or VR, Can you sticky this thread?

sure........... :ph34r:

[stetypeR]

Yo B16VTEC, top video i've always wondered exactly how it worked.:thumbsup: top post that :thumbsup:

[CleanGSR]

civic cee exx, on Feb 24 2006, 06:17 PM, said:

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.

[cranny]

gsr vtec engages at 5500 im pretty sure.

[CleanGSR]

No it's 4500 and you shouldn't argue with me on this one. I just drove my dad's GSR around all night last night so I'm 100% positive it's 4500.

This post has been edited by B16Vtec: 25 February 2006 - 02:29 PM

[Ben.]

cranny, on Feb 25 2006, 12:41 PM, said:

gsr vtec engages at 5500 im pretty sure.

No it's 4500.. Trust me, I found out the hard way. bleh

[SexyH22]

i think your wrong. its atleast 4600.

[CleanGSR]

B16Vtec, on Feb 25 2006, 08:39 AM, said:

A GSR's VTEC engages at around 4500 rpms.

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.

[Ben.]

B16Vtec, on Feb 25 2006, 03:41 PM, said:

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.

This post has been edited by civic cee exx: 25 February 2006 - 02:46 PM

[CleanGSR]

Your car would look 100 times better with a 98-01 teg front bumper. Still looks like it will be pretty nice though.

[xxscaxx]

yeah, i dont like front end swaps, but props for you for doing it.


oh, and btw, you should shrink your sig, before CRG rips ya a new one.


get that thing painted too.

[Ben.]

I plan on the 98 front end with an ITR lip..

Gotta figure out what I want for the Civic though.

[CleanGSR]

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.

[Ben.]

B16Vtec, on Feb 25 2006, 07:25 PM, said:

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.