Well I'm sure we've all seen the windshield banners, stickers, emblems, tattoos, and just about anything else you could possibly put on display bearing the word VTEC. It's just one of those things you know. Oh let's listen in on the typical VTEC conversation.

"Hey bro check out my Civic EX, I got big massive "VTEC" logo painted on both sides yo!"
"Daaayam! That's tight bro!"
"Hellz yeah biaatch! Now everyone will KNOW what's up!"
"How fast you runnin?"
"Shiiat, I don't know, prolly 14s. I'll be hittin 13s after my next mod tho."
"That'd be down bro, what's it gonna be?"
"I be gettin this new thing, where I can have my VTEC turned on ALL THE TIME!! HAHA!! No more waitin for that shiznit I'll be able to bust it out non stop yo!!"
"WHOA!!! That's crazy yo, how you gonna control that"
"Whatch you talkin about I can handle it, just cuz you don't got a 13 second demon don't mean you got to be hatin!"
"What?! I didn't say nothin! You too big to talk your bros now that you got this all time VTEC?"
"Pshh, you don't even know, once I start up that monster and hit VTEC at 2000 RPM I'll waste yo ayass, yo mama's ayass, shiaat, EVEEBODIES AYASS!!!"

After that, the guy with the fancy paintjob lost the next race...and the next one...and every race he ever raced again. A paintjob and a load of stupidity strangely didn't get him as far as he wanted to go.

VTEC, as most of us know, was a way to attack the compromise of low end power vs. high end power. It was pretty much impossible to make an engine with high output in the upper RPM range without sacrificing drivability in the lower RPM range. The physics of it work in a way such that a slower moving engine cycle responds better to low lifting valves with almost no overlap. However as the engine cycle speeds up and demand for air increases, the engine will need higher lifting valves with more overlap to meet the demand.

If you have high lift/overlapping valves at slow engine speed, the engine won't be able to expel waste gases fast enough before it breathes in again. So instead of the nice breath of combustible oxygen air your engine was expecting to get, it gets a load of its already burnt carbon monoxide gas. You'll notice this happening with a loss in low end torque as well as shaking, sputtering, and crackling when the engine is at idle.

On the other side, if you run low lift valves you'll get your nice idle and smooth response in the beginning. However as the engine spins faster, it can't circulate the air quick enough and the valves end up closing before the engine has completed breathing in all the air it needed. You'll notice this when your engine is pushed harder, and your acceleration seems to get weaker rather than stronger.

Every cam has only a single RPM in which the engine speed perfectly match with the cam lobe profile. You can usually tell how a cam was designed by looking at where the engine's torque peak occurs. The solution to that was to change the valve lift and timing on the fly, giving the driver excellent response at both ends of the RPM spectrum. Honda's solution was VTEC. An acronym that loosely stands for Variable valve Timing and lift with Electronic Control. Yeah I know they missed some letters, but VTEC just sounds cool so I guess they just picked the letters they felt like using for marketing sake.

There were a couple ways that Honda implemented VTEC, most of them actually for fuel economy believe it or not. However the DOHC VTEC system that we Integra owners are familiar was quite the opposite and created solely for performance. The Integra was lucky enough actually to be the first Honda ever to receive the DOHC VTEC engine in Japan back in 1989. The next year, the DOHC VTEC engine made it's debut in the U.S. inside the Acura NSX. Two years later in 1992 the Integra GS-R was born in the U.S. and the rest is history.

What you're looking at right now is a simplified 2-D representation of a look inside the head onto one of the 8 pairs of valves (lets say the intake valves) in a DOHC VTEC engine. The valves are in the closed position and currently there is no air being sucked into the combustion chamber Red = Camshaft Blue = Valve rockers Green = Valves White = Cylinder
As the cams spin around, the valves are then pushed into the open position and air is let into the combustion chamber Notice that the two smaller cam lobes actuate each valve individually while the large center lobe just actuates a rocker (lost motion assembly) which seems to be attached to nothing. The center cam lobe serves no purpose right now and just spins along with the camshaft . This is pretty much the normal operation of the valvetrain, and this cycle will continue until it is directed to do otherwise.
In order for the ECU to initiate the VTEC system, 5 engine conditions must be met. Temperature: The engine must have reached normal operating temperature. Throttle Position: The throttle must be open far enough to allow for increased airflow in VTEC. Vehicle Speed: The car must be in motion (wheels spinning). RPM: Engine must spin to it's target value. The GS-R will send it's "GO" signal for VTEC at 4400 RPM while the Type R sends it's signal at 5700 RPM. Oil Pressure: The engine must be operating with normal and safe levels of oil pressure determined by the VTEC pressure switch. The ECU will send a signal for a spool valve to open. When this valve opens, oil is allowed into the pivot shaft inside the valve rockers and directed into the center rocker. Inside the center rocker, a set of pins are forced outward by the oil pressure and lock inside the rockers to both sides. This entire process occurs in 1/10 of a second.
The valve rockers are now locked together and when the cams spin back around, the valves will be actuated by the single lobe in the center rather than being individually actuated by the smaller lobes. You can see from this picture that the valves now have much more lift when actuated by the center lobe compared to the smaller outer lobes. Not only have the valves increased in lift, they have also increased in duration, successfully altering the valve timing.
Once the engine decelerates, the oil pressure holding the pins outward will be cut off and a return spring will pull the pins back into the center rocker where they will lay in wait for the next trip into VTEC. The smaller cams will then take over and the engine will return to normal operation.

So that's it, not very complicated actually but an ingenious idea from a design standpoint. There was skepticism about all the small parts involved in the VTEC engine and most manufacturers believed Honda's new engines were going to be full of problems down the road with errors occurring during the VTEC engagement process. However it turned out to be quite the opposite as DOHC VTEC engines have proved to be some of the most reliable engines ever built because of their precision.

Now that you know about the basic VTEC system, check out the i-VTEC article at the Temple of VTEC for information on the newer i-VTEC system used in the Gen4 Integra (RSX) motor. The next page will show the GS-R's dual stage intake manifold and how it relates to VTEC.

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