What is vtec?

[The underachiever]

A lot of magazines and people talk about VTEC and how good it is but can someone tell me what it exactly is or does? I know that it increases performance and reduces emissions but it would be a great deal of help if someone explained how it works. Thanx.  

[0verb00st]

it's honda's form of variable valve timing....

[PlastikPaul]

VTEC:Variable Valve Timing and Emission Control

Cars without VTEC runs well at low RPM.

Cars with VTEC runs well at low RPM and high RPM.

 

 

So when driving at city street speed VTEC stays idle, the valves doesnt open as far and stays open 4 a short time. The reason 4 this is to save gas and perform more effectively at low RPM.

 

 

When driving fast VTEC kicks in, the valves open wide and stay open longer. This is 2 give the engine all the fuel-air mixture it needs.

[theachiever]

VTEC:Variable Valve Timing and Emission Control

vtec stands for variable valve timing and electronic lift control

[0verb00st]

the acura RSX type S has the new ivtec engine (intelligent vtec). it has a much broader powerband and and makes adjustments to the cam, crank, and timing while driving. this makes it more efficient and brings a lot more power to the low rpms (and higher rpms too).

[TrueSi]

yup thats VTEC

[XScarAudio]

the type s rsx is nothing special....i test drove one a month ago looking to buy one......wasnt that impressed for the $

[Drew]

Hopefully, they will be bringing the Type-R here for 2003.  That would be pretty sweet...

[XScarAudio]

vtec is those people that make the phones right??? :worry:  jfwy.......(its electronic lift control btw)  

 

i once heard some kids ask someone if their car had vtec....they playfully responded "yup, i have 2 of them" and the kids were like, "woah, that must be mad fast!  how much boost?"  lol.......vtec is great for what it is, but what it is, is a way to make a small displacement engine have a more agressive intake cam at higher RPM's....nice, but not by anymeans a turbocharger!

[TrueSi]

Hahaha  :chops:  :chops:  I would have laugh my a** off if someone tells me that. But you'll be surprise of some of the things I've heard at my shop one of the greatest of them is this guy that came to my shop he wanted to buy stainless steel valves because someone had told him that they would increase Horse Power    I try to thought him out of that Idea but he insisted so I sold him the valves he went home and 3 days later he came back because he couldnt find where the valves were. LOL

[alf]

i read somewhere vtec is Valve Timing Electronic Control. but they gave the same description

[XScarAudio]

yeah...only difference, is the variable in there....bc valve timing is set by the timing belt!

[Toda Party]

i wrote this a while back in another forum but...should do the job

 

 

VTEC - Variable valve Timing and lift Electronic Control

 

To fully understand VTEC, you first have to know basically how a traditional 4-stroke piston engine makes power. For that, refer here:

 

http://www.howstuffworks.com/engine.htm

 

 

On top of that, you must know how a camshaft works: http://www.howstuffworks.com/camshaft.htm

 

 

After you have read these links, or if u already know basically how an engine and camshaft function, continue...

 

Traditionally, on DOHC non-vtec motors, a typical camshaft looks like the following:

that's a VW cam, but a Honda non-vtec cam looks pretty much the same.

 

2 Lobes per cylinder, a primary and secondary lobe. Each lobe acts upon the rocker arm (pushes down on it). When the rocker arm is pushed down, the other end of it, where the valve is connected to, the valve opens up a certain distance from its resting position. This is called Valve Lift

 

Along with a valve lift specification, cam lobes are also measured in what is called Duration which is, basically how long the lobe keeps the valve open over a 360 degree range, since the cam rotates, they measure it in a circular style, like this: And so the degree measurement is of the blue. EDIT I just realized the pic is wrong...the red is the time when the lobes are not acting on the rocker arms...thats why they stay closed...not because some additional lobe is keeping them closed. Sorry bout that.

 

 

 

So here's what a normal VTEC cam looks like. I think these are b16 cams, but I can't tell from this pic.

 

here's a normal picture:

 

Notice the BIG cam lobe that is sandwhiched between the primary and secondary smaller lobes. That big meaty cam lobe is the VTEC lobe.

 

Now think about it. Normally, the primary and secondary lobes just rotate and open valves, and there's no middle lobe to complicate things. But now, you have a middle lobe...but how does that lobe take control over the non-vtec lobes?

 

This is where you hear the term VTEC crossover...the point at which the VTEC lobe is engaged.

 

This is achieved by the ECU reading a variety of different sensors, most importantly, Oil Pressure, Water Temperature, Engine Speed, Throttle Position, and some others. When all these systems show ready, a PIN is pushed through all three of the Rocker Arms per cylinder, so that it is now in reality one BIG rocker arm. And since the VTEC lobe is much bigger than either the primary or secondary lobes, its like there is only one single cam lobe instead of the previous two.

 

This brings me to some side points that I'd like to address:

 

 

- Overlap - When you have aggressive cams geared towards making power w/o the aid of Forced induction, they tend to have high lift and long duration. Along with the long duration, you have a long overlap - the amount of time both the intake AND exhaust valves are open. Long overlap tends to make the motor lose a bit of compression, since the exhaust valves are still open when the piston begins its compression stroke, some air/fuel mixture is lost out the exhaust valves. Hence, when upgrading to aggressive cams, increasing the compression ratio to make up for this loss is a good idea, or else you won't be taking full advantage of those cams.

 

- Upgrading the Valvesprings - When you upgrade to a cam with higher lift characteristics, you obviously want the valve train to handle it..otherwise, the springs bind and you don't achieve the maximum lift of that cam.

 

- Setting VTEC Crossover point -

 

VTEC engagement on a stock car is OPTIMIZED. Do NOT f*ck with it because all you are really doing is taking away power, depsite what it "feels" like

 

Now that we have that cleared up...YES, i know that bringing the VTEC crossover up or down around 500 or even 1000 rpm up or down may indeed improve your power curves. Again, this is something u can only really prove if you are on a dyno and u can see the immediate results.

 

So, why do you need a vtec controller? U dont, really. Unless you are using aftermarket cams, or have upped the compression, or some other internal modification that demands a shift in the VTEC x-over to again be optimized. AGAIN, something you should really be doing on the dyno, as every motor is different, not to mention weather conditions, grade of gasoiline, general condition of the motor, etc....

 

So when you hear people say "I got a vtec controller and i set vtec to 3,000 rpm so im maddddd fast now son" u know they're a f*cking idiot.

 

Why? This leads into my explanation on how vtec works but basically....

 

on a vtec motor there is a vtec cam lobe and non vtec primary & secondary cam lobes. Those non vtec lobes are optimized for low end power delivery. However, @ upper RPM, the small lobes cannot deliver enough air nor keep the valves open long enough to continue to let the motor make power.

 

Hence, the VTEC crossover...where the VTEC cam lobe takes over duties in opening and closing the valves from the seconary and primary lobes. Since the vtec cam lobe is much taller, it can now provide more air and duration the motor needs to keep making power @ higher RPM.

 

Now think about it. What does setting VTEC at 3,000 rpm do? It makes a cam lobe designed to work well at HIGH rpm to work at LOW rpm. Conversely, setting VTEC too high will cause the motor to start dying out, then JUMP foward when the VTEC lobes take over.

 

Its like asking allen iverson to play center against shaq. it doesnt make sense, and therefore, people shouldnt do it cuz its pointless.

 

If u have or do get a vtec controller, try it one day.

 

Set vtec to 3,000 and see how much of a pig the car is down low. Then set vtec to say 7,500 rpm or something. See how the car accelerates, slows down, then springs foward again at vtec x-over.

 

you may think that is the car making more power, but if you were to look at dyno graphs, you would see the torque curve fall off, then rise back up @ your specified vtec cross over point.

 

the above is also a good way to determine a starting point for an optimal vtec x-over when you have done some internal mods and u would like to set vtec @ a certain point. Take a dyno pull with vtec set low, then another pull with vtec set really high.

 

Overlap the graphs and where the curves intersect where power falls off and where power comes up is where you should start to f*ck around with a crossover point

 

 

 

 

 

Now, I-VTEC is VTEC, with a twist. Toyota's VVTL-i is the same thing as i-VTEC. Basically, in addition to VTEC, the ECU reads and modifies both intake and exhaust cam timing to an optimal point at every point on the RPM band. This ensures the most efficient cam timing to achieve optimal hp and torque. Infinitely Variable valve Timing and lift Electronic Control. This is why the new RSX-S motors, although only making 5 more hp than the old Type-R motors, are making around 12 more lb-ft of torque - because of i-vtec.

 

Also realize that VTEC and i-VTEC, altho refined and marketed by Honda, is nothing THAT new. I think some mercedes models first used variable valve timing back in the 50's or 60's...and in today's market, Ferrari, BMW, Toyota, Nissan, Honda, and many other manufacturers use some variation of variable valve timing. If you think about it, although complex and expensive both to reasearch and develop, a variable valve and cam timing system has no competition from a fixed valve timing and fixed cam timing system. Pretty soon, all cars in the market will have variable valve and cam timing, not only does it help with making power, as I'm sure you're all concerned, but since it is more efficient, it cuts down on pollution and smog as well.

[Trepid]

wow! that's pretty cool, a lot of good info there

 

I'm impressed

[EGRacer]

lol that hurts my eyes. to much to read

[Drew]

I'm sure you already know it all ZC

[XScarAudio]

lots o good info!

[ek9]

very informative. make it a sticky.

[EGRacer]

o yea right. me know it all hahaha funny. i wish i did. cause then i would have to buy honda in 40 years after i become a billionaire selling information on hondas

[cranny]

actually vtech is electronic , and it constantly sets your timing through your rpm. If anyone has ever worked on an older car like a 302 ford for instance inside the distributor , which newer hondas do not have anymore, as the engine turns faster rpm the centrifugal action of the distributor turning adjusts the timing to run more efficient at that higher rpm. Vtech sort of the same thing but electronic , the vacuum days are OVER!!! SO for a runup the spark timing of an engine at idle to 3000 rpm is not as effective when revs higher, thus the japs though of somin else ingenious.

[BigBirdSucks]

actually vtech is electronic , and it constantly sets your timing through your rpm. If anyone has ever worked on an older car like a 302 ford for instance inside the distributor , which newer hondas do not have anymore, as the engine turns faster rpm the centrifugal action of the distributor turning adjusts the timing to run more efficient at that higher rpm. Vtech sort of the same thing but electronic , the vacuum days are OVER!!! SO for a runup the spark timing of an engine at idle to 3000 rpm is not as effective when revs higher, thus the japs though of somin else ingenious.

it's VTEC

[optional187]

lol...someone's a retard for bringing back a thread thats about 3 years old.

[cranny]

i dont hear anyone disputin my views just my spelling, ???? are you kiddin me, just tryin to help people my man keep people informed, half you guys prolly never picked up a ratchet in your life.By the way toda awsome writeup man very imformitive.

[SexyH22]

i dont hear anyone disputin my views just my spelling, ???? are you kiddin me, just tryin to help people my man keep people informed, half you guys prolly never picked up a ratchet in your life.By the way toda awsome writeup man very imformitive.

whats a ratchet, and why would i want to pick one up?

[optional187]

i dont hear anyone disputin my views just my spelling, ???? are you kiddin me, just tryin to help people my man keep people informed, half you guys prolly never picked up a ratchet in your life.By the way toda awsome writeup man very imformitive.

toda hasn't posted on this board in years. thats YEARS.

 

do us all a favor, if the thread is older than a month old...leave it alone.