about vtec

[matt81]

I want to know about vtec in detail.how it works, the different between vtec and turbocharger and so forth.can someone help me?

[yougod10]

What VTec basically does it allow the valves on a car to open for longer periods of time during specific intervals. So during high revs allows more intake/exhaust to enter the engine block.
SOHC engines only have VTec on the intake side while DOHC engines have it on both intake and exhaust valves.
If I remember correcty, there's a VTec solenoid right by the distributor which controls a seperate camshaft. This shaft has the same 2 intake/exhaust lobes but has a 3rd one that has a larger and longer lift than the other 2. So during the higher rpm range the 1st and 2nd valves run off the 3rd (the 1st and 2nd dont contact there lobes until the 3rd is disabled).

There are many differences between turbo and vtec. So many that they usually can't be compared to one another. Turbo can be set to an unlimited amount until your engine explodes while VTec can be set to engage/disengage at different points. The VTec system will give you the extra torque/hp without sacrificing fuel economy.

Post if you have more specific questions because there is such a broad range of answers I just can't cover them all.

[matt81]

thanks.i have heard that the vtec has 2 categories refering to the colour of the engine cover colour whether red or black? isn't it right? can a vtec engine do the accelerate as the turbo one?

[civickiller]

vtec only adds about 15hp, turbos add like 50hp. turbo better

[hybridsol]

The Honda VTEC system actually uses two camshafts, one that is setup for low RPM operation, while the second operates at high RPMs. This allows the Honda engine to produce good low end torque, while also providing lots of breathing room and horsepower for high RPM operation. To tell you the truth VTEC in in constant study and advancement, soon it will be up to turbo hp maybe even further.
Traditionally in the North American marketplace, engines have been built for torque, rather than horsepower. As a rule, larger bore equals more horsepower, while a longer stroke equals more torque. A long stroke allows the engine to produce power for a longer period of time, and subsequently more torque. There is a drawback to a long stroke however. Because the piston must travel a longer distance, there is a physical limit to how many RPM the engine can achieve. On the opposite end of the spectrum, an engine with a large bore and short stroke will produce less overall torque, but has the ability to reach much higher revolutions per minute, and subsequently more horsepower.
While the domestic manufacturers have traditionally built engines with lots of torque, the German and Japanese manufacturers have been building engines with less torque, but the ability to rev much higher. This typically means that import cars don't accelerate as quickly right off the line as their domestic counterparts, but they are able to accelerate for longer in the same gear. In the near future VTEC will be replacement of displacement. BMW also has a VAMOS system that is very simular to the vtec system still in advancement. Dont know if your farmiliar with VAMOS?

There is no Holy Grail of engine design. The engine builder's creed used to be "There is no replacement for displacement". Perhaps now a more appropriate phrase is "There is no replacement for displacement, except technology".

[matt81]

thanks for the explainations. what is VAMOS? can you explain to me technically? is VAMOS is new technology? can vtec engine equipped with turbo kit? has someone try it before?

[hybridsol]

misspelled its vanos, sorry bout that. in reply to your post. In 1993, BMW first released an engine utilizing VANOS in the M50 2.5 L model. Initially, the incorporation of VANOS was limited to the intake valve. VANOS (as it is now known) is infinitely variable cam timing on the intake valve. With VANOS, the camshaft has the ability, through complex gearing, to open the intake valves earlier into the intake stroke, allowing the engine to breathe in more air during high RPM operation, and thus produce more high RPM power. In the Beginning of 1996 with the 3.2L Euro motor, BMW offered Double-VANOS, which simply duplicated the VANOS system on the exhaust valves. last year and this year BMW upped the stakes and introduced Valvetronic. Valvetronic takes the previous idea of infinitely variable valve timing, and adds in infinitely variable valve LIFT. In other words, Valvetronic controls how far the valve opens depending upon how hard the driver is squeezing the throttle. A standard camshaft and rocker arm are still in place, but there is now an intermediary arm in between. This intermediary arm pivots based on throttle input, allowing the camshaft to open the intake valves steplessly as little or as much as the system demands. One of the major benefits of this system is the total elimination of the throttle butterfly. This means that the valves themselves are the only things controlling the amount of air flowing into each cylinder. With this system the intake manifold remains full of air the whole time, allowing much faster throttle response. In short displacement is slowly being replaced by technology. Also yes it is possible to equip a honda with vtec with a turbo..... a turbo uses exaust gases to spool a turbine to force air into the intake, vtec is completely different, Vtec is all valve timeing.
good luck.

[higgimonster]

Just to clear up some stuff. vtec does not switch to a new cam shaft it just activates a new cam on the shaft already. This pic should help explain.
BTW, this pic is from herre: http://integra.vtec.net/geeser/vtec.html

[hybridsol]

Originally posted by higgimonster
Just to clear up some stuff. vtec does not switch to a new cam shaft it just activates a new cam on the shaft already. This pic should help explain.
BTW, this pic is from herre: http://integra.vtec.net/geeser/vtec.html

I probably just missed something but who said that it switches?

[higgimonster]

Quote:
The Honda VTEC system actually uses two camshafts, one that is setup for low RPM operation, while the second operates at high RPMs.

Ok, nobody ever said switch. But I just wanted to clear up the thing about a seperate shaft. No biggie.

That valvetronic thing sounds pretty cool. I knew they had a sytem like that but I wasn't sure how it worked. I am waiting for the next generation of camless valves to come out. Using electromagnets and stuff. That will make things crazy (my uber-technical terminology must be astounding you :licker: )

One of the other really interesting developments in engine-tech coming soon will be in Saab's variable compression engine. With a displacement of something like 1.3L and producing 225hp (don't quote me but I am pretty sure those numbers are mostly accurate). It is a really interesting design.

[delsolsi]

As higgimonster's pic shows there is not a seperate cam for VTEC. At lower RPM's the valves run off the primary lobe and the secondary lobe. When you get to higher RPM's usually around 5000, the valves switch over the the VTEC lobe in the middle. I'm not 100% sure what this switch involves, but I think when you hit your VTEC RPM the VTEC selenoid locks the rocker arms for the valves into a position to run off the VTEC lobe instead of the primary and secondary lobes. The VTEC activation point can be adjusted with VTEC controllers. The idea of VTEC is to have the best of both worlds with your cams. Normaly the cams that come stock on cars idle nice and make good emissions, but they dont perform very well at high RPM. When you put a higher lift and duration cam in your car, your idle sucks and your emissions suck, but your car now makes alot more power at the top of the RPM range. VTEC allows you to have both a good idle and good emissions at low RPM and make lots of power at the top of the RPM range. The best of both worlds.

Also I'm not sure but I think the system Toyota uses in the Celica GTS is very similar to VTEC. And I think Mitsubishi has a similar system on some of their JDM stuff, because when I bought a Field VTEC controller a five years ago it had directions for both Honda and Mitsubishi.

[hybridsol]

Originally posted by higgimonster
Quote:
The Honda VTEC system actually uses two camshafts, one that is setup for low RPM operation, while the second operates at high RPMs.

Ok, nobody ever said switch. But I just wanted to clear up the thing about a seperate shaft. No biggie.

That valvetronic thing sounds pretty cool. I knew they had a sytem like that but I wasn't sure how it worked. I am waiting for the next generation of camless valves to come out. Using electromagnets and stuff. That will make things crazy (my uber-technical terminology must be astounding you :licker: )

One of the other really interesting developments in engine-tech coming soon will be in Saab's variable compression engine. With a displacement of something like 1.3L and producing 225hp (don't quote me but I am pretty sure those numbers are mostly accurate). It is a really interesting design.

im actually very farmiliar with (EVT) Electromechanical Valve Train
and yes the saab motor does kickass the SVC is a motor built to improve fuel efficiency by up to 30 percent, reduces tailpipe emissions, and doesn't negatively impact overall performance. (Saab Variable Compression) (SVC). The SVC engine first introduced at Geneva in 2000 was a supercharged, 1.6-liter, inline five-cylinder engine. With dual-overhead camshafts and four valves-per-cylinder, it looks pretty much like your average internal combustion engine. In fact, an objective in the development work on the SVC was to retain as many of the basic components of a conventional engine as possible. The crankshaft, connecting rods, pistons and valves are all of the same type as those of today's engines. What distinguishes the SVC engine is the way it is split into upper and lower parts. Instead of having the cylinders located in the block like all modern vehicle engines, the SVC engine's cylinders are located in the upper section. This upper part is known as the monohead. You heard me right -- [the cylinders are built into the head] crazy stuff. For those of you who may not know it, this is a very unconventional design. Traditional engine architecture places the cylinders below the head (or heads if the engine is of a V or flat configuration), between the valves and the block. Everything else is pretty "normal" inside the Saab engine. The lower portion of the SVC engine -- the block -- contains the crankshaft, camshaft and pistons. But here's the kickass part. Since the cylinders are built into the heads, the monohead can be adjusted (moved) relative to the block without affecting engine or valve timing. On the SVC engine, the monohead tilts at up to a 4-degree angle. Rubber bellows seal the monohead to the block. By adjusting the "slope" of the upper part of the motor in relation to the lower part by the use of hydraulic actuators, the Saab engine can vary the volume of the combustion chambers. This, in turn, changes the compression ratio. Compression ratio for those here who arent farmiliar???? refers to the ratio between the combined volume of a cylinder and a combustion chamber when the piston is at the bottom of its stroke, and the volume when the piston is at the top of its stroke. The higher the compression ratio, the more mechanical energy an engine can squeeze from its air-fuel mixture. Higher compression ratios, however, also make detonation more likely. In all modern engines, the compression ratio is fixed and cannot be altered unless different engine components are installed. Saab's SVC technology allows a variable compression ratio from a low of 8:1 to a maximum of 14:1. Although variable compression is what makes the SVC engine unique, Saab claims the fuel efficiency of a conventional, normally aspirated engine would only improve by 4 percent if it were equipped solely with SVC. The potential of variable compression is most effective when combined with a smaller engine design (for better efficiency) and high supercharging pressure. the engine measures up at 1.6-liter SVC generating 225 horsepower and 224 foot-pounds of torque. Maximum boost pressure from the supercharger is 40 psi. These horsepower and torque figures are comparable to a na engine of similar displacement (like a 3.0-liter V6 from a Nissan Maxima, for instance). Additionally, the SVC engine is more fuel efficient at light loads than a standard 1.6-liter normally aspirated engine. Due to its variable compression ratio, the SVC engine can run at an optimum compression ratio of 14:1 at low engine loads to maximize fuel efficiency and lower harmful tailpipe emissions. Increased supercharger pressure at such a high compression ratio would cause detonation, so the compression ratio is lowered to 8:1 at high engine loads to enable maximum engine performance. The SVC engine continuously varies the compression ratio according to driving conditions. This would not be possible, however, without an advanced engine management system or (Trionic engine management system) is put to making the whole thing work. The current system, which Saab has been using since 1991 to manage their turbocharged engines, served as the basis for the specially designed SVC system......now that ive just bored you all to death let me apolagize......sorry I did a paper on it last year..... and the car is no longer a concept.

[SmoovSol]

[quote]Originally posted by hybridsol
[b]The Honda VTEC system actually uses two camshafts, one that is setup for low RPM operation, while the second operates at high RPMs.

DONT WORRY, I know u meant cam lobe and not cam shaft honda uses to achieve that oh so great vtec, problem is not just honda has it, toyota's patent is actually a nicer one. VVTL-i works on the same basis but turns the cam over to suck in more air when full acceleration is underwent, lol everyone has vtec, ford zetec, honda vtec, chrysler Gtech, toyota vvtl-i, and bmw with there more advanced vanos.....Lol, I can guarentee there are only about 12-18 real mechanics on here, I know some people read a couple articles and have some honda books and think they know. Another cam? SO they have 4 cams? they would need 4 cams in order to switch to a better one at higher rpms, oh u must mean it turns over to a larger cam lobe, right right. Type-o... Mechanics get payed to work on these marvelous machines and are disrespected everyday by people who come walkin in slinging all the techno babble they got out of the last issue of car and driver.. Please stop thats all i ask, thats one of the reasons i stopped coming on here. As for the people that do offer the advice and are confident in what there sayin is true, happy posting....

[SmoovSol]

sorry for flaming but a new kids walks in everyday that tried to tell one of us whats wrong with his car or how he knows this. It gets agravating so I vent my anger on here. Lol, but i still mean what i said about those people who know who they are.......... yah!

[SmoovSol]

Originally posted by higgimonster
Just to clear up some stuff. vtec does not switch to a new cam shaft it just activates a new cam on the shaft already. This pic should help explain.
BTW, this pic is from herre: http://integra.vtec.net/geeser/vtec.html

I am going to blow that freakin picture up and bring that thing to work so whenever anyone comes in askin about vtec I will just point to tha sign. Thanks higgi, this should help alot....