what the hell is a Vtec?

[DarcSystems]

As far as I know, people with Vtec motors promote it as a performance feature. From what I read, all it really does is help with gas mileage at higher speeds.

I'm not 100% sure of the details of how it works, which is why I'm asking before jumping to conclusions. What I assume it is is at a certain RPM or speed, the cam uses a different lobe to control the intake or exhaust valves or something.

I dunno, if someone could clear it up, it would be appreciated.

Thanks
-Jay

[BlitzNuRspec]

Basically just hondas variable valve timing. At 4800rpm, the upper cam lobes open up, allowing more air into the engine.

[FatBastard]

yes, basically it allows both exhaust and intake valve to be open at higher RPMs.
(not much, but still...)

on lower RPMs this would only cause it to run bad, but on higher RPMs (that is, when the kinetic energy of the gas/air is high enough to "move by itself") you can leave the exhaust valve open (when the intake valve opens!) to let the cylinders fill up more freely.

this is how i understand it. not sure if i could explain it right though... :rolleyes:

[lude4life]

Variable valve Timing and lift Electronic Control

and no, Vtec SUCKS the gas. Doesnt help gas mileage.

This pretty much sums it up.
http://auto.howstuffworks.com/framed.htm?parent=question229.htm&url=http://www.leecao.com/honda/vtec/whatsvtec.html

[kms8489]

yes. they suck gas...this will explain EVERYTHING! http://www.streetracersonline.com/articles/camshafts/index.php

at the bottom of the page are links to more on VVT/camshafts/ whatever

[Biggentplayer]

Basicaly it is giving you a burst of speed at the high rpms. I have a civic si and if you do not have at least a quarter tank of gas (i heared) the VTEC will not kick in.

[pat99872]

Variable valve Timing and lift Electronic Control

and no, Vtec SUCKS the gas. Doesnt help gas mileage.

This pretty much sums it up.
http://auto.howstuffworks.com/framed.htm?parent=question229.htm&url=http://www.leecao.com/honda/vtec/whatsvtec.html
its only when vtec engages. if your easy on the gas your fine

[Biggentplayer]

I am sorry to get off subject here but i just bought my civic si last week. Today was the first time i have refueled it and realized that Si only takes Premium gas. Damn it cost 1.90 per gallon. :banghead:

[Zach]

I am sorry to get off subject here but i just bought my civic si last week. Today was the first time i have refueled it and realized that Si only takes Premium gas. Damn it cost 1.90 per gallon. :banghead:
DAMN! Where do you get your gas??? It costs like $2.10 at least here in Cincinnati.

[PimPmyRide]

i know for reals man normal gas here is 2.04 a gallon and premium is like 2.19a gallon

[Bartok]

Ah, the pleasure of living in one of the lowest cost-of-living cities in the USA...

87 octane is around $1.70 here.

[wataba]

yeah the camshafts have 2 lobes and at a certain rpm, depending on how much you're on the gas, it will engage the second lobe for higher lift. it used to be some pretty cool technology but everyone has it now. some manufacturers, at least ferrari and porsche that i know of, i think they have a slanted lobe so that they have continuous variable valve timing whereas vtec is more like an on/off switch

[T0626N]

i know for reals man normal gas here is 2.04 a gallon and premium is like 2.19a gallon

Hah! I haven't seen gas that cheap in a while. It's $2.47 here for Premium. BTW i live in Southern California, what a rip... :banghead:

[Kazimierz]

O'ahu is 2.40 to 2.60 depending where you are, for premium. I hear the other islands are pushing 2.80 and more.

[ramittinbawdeep]

oh you lucky buggers. moaning because petrol is only $2 a gallon or so :D
try paying at the current exchange levels and a gallon being 4.56 litres
we pay for super unleaded(premium) 90pence = £4.10 a gallon which in us money is $ 7.38 a bloody gallon think yourself lucky,

[Boostedpimp]

Hah! I haven't seen gas that cheap in a while. It's $2.47 here for Premium. BTW i live in Southern California, what a rip... :banghead:


LOL that does suck man.. isn't your highest octane rating out there only 91? that's lame.. I can get 94 at the pump here if i wanted to but it's priced high. I could simply get 115 octane for the same price at a few select pump stations for about the same price or two cents different a gallon.

[MrSlippyFist]

Ah, the pleasure of living in one of the lowest cost-of-living cities in the USA...

87 octane is around $1.70 here.


what city do u live in so i can live there when i move out? low gas prices=paradise

[kms8489]

when i was in the bahamas the gas was 5 bucks a gallon. here in winston-salem, nc its $2.15 for premium

[civictunerz]

As far as I know, people with Vtec motors promote it as a performance feature. From what I read, all it really does is help with gas mileage at higher speeds.

I'm not 100% sure of the details of how it works, which is why I'm asking before jumping to conclusions. What I assume it is is at a certain RPM or speed, the cam uses a different lobe to control the intake or exhaust valves or something.

I dunno, if someone could clear it up, it would be appreciated.

Thanks
-Jay
Main > Auto > ShortStuff

This is how a vtec works...






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:



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... I own a 2000 civic si, it's alright on gas, i fill it up every week, it takes about 20 dollars here in texas, gas is $1.93. Hope this info helped you better. Later.

[civictunerz]

I am sorry to get off subject here but i just bought my civic si last week. Today was the first time i have refueled it and realized that Si only takes Premium gas. Damn it cost 1.90 per gallon. :banghead:

Hey i own a 2000 civic si, i use the mid-grade gas, but i clean it once a week, to hell with paying $2.14 cents a galloon for premium! :banghead:

[oneloveevo]

what the hell does cleaning your car have to do with the gas you get!? :wtf:

[FatBastard]

Hey i own a 2000 civic si, i use the mid-grade gas, but i clean it once a week, to hell with paying $2.14 cents a galloon for premium! :banghead:

u clean it every week? like valves, exhaust and everything? that´s alot of work for running on lower octane...

isn´t the problem mostly the fact that running on too low octane => bad combustion => large amounts of crap in exhaust valves -> (arrow meaning, everything forward from it...)


P.S. dammit i hate it when i don´t know the names of parts in english... can´t get my questions right!! :banghead:

[Brad6510]

what city do u live in so i can live there when i move out? low gas prices=paradise
you want cheap gas?? come to alberta man, our premium is at 82.9 cents a liter

[civictunerz]

what the hell does cleaning your car have to do with the gas you get!? :wtf:


I clean my fuel tank you dumb ass.

[civictunerz]

you want cheap gas?? come to alberta man, our premium is at 82.9 cents a liter



Yea but put that in american money and that 2.12 or sumthing.

[FatBastard]

I clean my fuel tank you dumb ass.


why the hell, u dumbass?? :D

or do they put sand and crap in low-octane fuel in the states?

[Senor_Queso]

I feel special. Gas still costs about $1.50 here.

EDIT: Aww... My 100th post and I didn't use it telling someone off. :(

EDIT: civictunerz, learn to use the fucking edit button. You double-posted TWICE. You, sir, are a dumbass.

EDIT: My 100th post wasn't for nothing now! :)

[Biggentplayer]

Hey guys gas just droped to 1.73 a gallon for premium. :bang: