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ok... some of the stuff I'm about to say is in perspective... it in no way makes my car actually fast....
It's pretty obvious that VTEC works better under certain conditions... there are some times where you can barely notice anything, and other times where when it shifts, it sounds kinda pissed off, like it almost means business and is trying to do something. I've been trying to figure out if there was anything to set it off to do that (air temp, gas in the tank, driving time, speed, gear), and honestly I can't. The only thing I do notice is then it's "Happy" theres about 95 psi of oil pressure (from about 6000 up), and when it's not it usually hangs around 90. But something has to make it do this... I know the system works off oil lines, so I'm guessing the temperature of the oil has something to do with the little extra kick that sometimes happens. So does anyone know what temperature VTEC works best at? Just curious if there's a magic number and if there is... then I might just have to start looking for a way to keep it there.

 
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i've driven almost all Honda VTEC cars and cam switching is unnoticable, sometimes i can feel it when i step lightly on the throttle (maybe throttle position sensor). But if you wanna get most out of VTEC, go buy a new set of cams.

 
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This is going to sound stupid but, around what actual rpms does the vtec kick in at? Like yesterday, I wanted to really feel the vtec kick in, and between each shift i let the rpm's reach some 5500-6300 rpms and I didn't really feel much of a difference? Surely it would have kicked in by then. Anywho, does anyone know the actual rpm? thanx

 
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actual rpm varies, depending on controllers for v-tec but stock would be around 4500-5700

Injen

 
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It likes a lot of air. On most VTEC equipped cars you will not notice the VTEC, unless you pay attention to the Tach gauge. You will see the RPMs pic up faster on a steady throttle. On the higher horsepower VTEC cars, you will feel the difference. You see the difference in 2nd and 3rd gear on the tach. To see it 4th you will need a lot more horsepower. Adding a CAI to and RSX type-S motor brings it up to Type-R status. VTEC loves to breath and does not care too much about exhaling.

 
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My understanding is VTEC works off of oil pressure rather the oil temp. Once you reach a certain oil pressure the cams kick into VTEC.

 
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Yes, the solenoid does work off oil pressure, but it also will not turn on until the oil reaches a certain temperature. From there, the oil will continue to increase in temp. But somewhere between the VTEC activation temperature and the maximum that it can reach, there is some ideal oil temperature. The temperature has some effect on the pressure (higher temp usually gives higher pressure), but it gets a little messier than just that. Since the oil pump is tied to the engine speed, it will pump harder the faster the engine runs, which pushes the oil pressure up... but then the oil passage for VTEC opens, which increases the volume of the oil passages. I theory, the pressure should drop off... UNLESS, the oil expands faster than you can increase the volume, if this is the case then the pressure will increase. So, there has to be some value that causes the oil to flood the passageway almost instantaneously...
I think I dug myself in over my head on this one... it's getting a little bit more complicated that I think I can figure out. It started off fairly simple, but the more I think of all the factors that go into making VTEC work, the worse it gets, and the more I envy Honda engneering for getting it to work.

 
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Hrmm.. I wonder if what your referring to is a some sort of safety feature. Meaning that the VTEC solenoidwill only be used when the oil has reached a certain temp. Thats the only reason why I can fathom why oil temp would have anything to do with VTEC engagement.

To elaborate on my first post above, when the engine is not in VTEC its using only the primary valves and cam lobes. Once you increase throttle and the oil pressure reaches a certain amount, the VTEC solenoid kicks in and locks the secondary valves and lobes for VTEC mode. I dont recall ever hearing that there was additonal oil passages that opened up... not sure.

 
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The temperature is a safety feature... works differently in different cars. In ours, it just won't engage VTEC, in S2ks it puts a rev-limiter at 6K, it just won't let you rev any higher to protect the engine.
I may just be confused as to exactly how is activated... I'm under the impression the solenoid opens an oil passage in the head which fills and the pressure locks in the lifters for the Vtec lobes. I could be wrong and it's all electrically done.

 
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goota love the VTEC