Well, not really. If you wanna have a way to think of it, think of it like having a one cam for gas mileage while cruiseing, and one cam for power mid-range and up. We have DOHC, and we can phase them relative to each other so we dont have to rip the motor apart to put in our "agressive" cam. The VTC does it for us. Its pretty complicate for the uninitated, but I can help.Niss200SXGTR said:think of it as a cheap ass supercharger..
The VTC has nothing to do with ignition timming. Only cam phasing. Like I said before its all about cam overlap. Lets define the term cam overlap in simple terms.V i V i D 200sx said:VTC only varies cam timing. its like the "i" in "i-VTEC" it allows the intake and exhaust cam to stay open variable amounts of time, relative to eachother: for better efficiency(overlap, like the previous post stated). there are 3 VTC phases. (these are off the top of my head) 3400, 5000, and 6700. at 3400, VTC retards timing, b/c @ lower RPM, you dont need highly-advanced timing. at 5000, VTC advances timing, b/c @ higher RPM, the engine is moving so fast, that advancing ignition helps in getting a complete burn. @ 6700, VTC retards again, so that it degrades power slightly (ga16 doesnt even make great power anyway) and encourages an upshift, just before redline. JWT can alter these VTC shift points or get rid of the last one, b/c there is no good in it being there.
BTW VTEC stands for variable valve timing w/ electronic lift control. this is how you get a "big cam and a little cam on one camshaft" it has 2 lobes: one for low-rpm and one for high-rpm. the low-rpm lobes have lower valve lift, and they stay open for a shorter amount of time... (lower demand for fuel) the high-rpm lobes allow for longer valve lift and they stay open slightly longer, due to higher fuel demand. but VTEC is like a step, not progressive... which is why you get that "VTEC kick." i think most of the german variable valve timing systems and the newer-generation ones like VVT-I (toyota) and i-VTEC (honda) are more progressive, (almost infinately so) so you dont get a nice kick anymore.
VTC does not have the ability to vary valve timing and lift. i believe the new Q-series nissan motors do (qr25, qg35) or in japan, i think the NEO VVL motors do this.