VTEC is NOT about Variable Valve Timing - its about valve lift!

[e30pwr]

STOP mixing VTEC with VVT!

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.

[I]It's true that the engine's valve timing changes, but that's a secondary to the primary objective of VTEC - which is valve lift.

wait a minute, VTEC by their definition does change the valve timing? Even if its a secondary function it still performs it correct? excuse the lack of knowledge on the topic.

[5speed]

wait a minute, VTEC by their definition does change the valve timing? Even if its a secondary function it still performs it correct? excuse the lack of knowledge on the topic.

Yes, it is a secondary function. It is only done in order to cause the primary function.

[Atlblkz06]

wait a minute, VTEC by their definition does change the valve timing? Even if its a secondary function it still performs it correct? excuse the lack of knowledge on the topic.

Well, it does not "change" valve timing. It pretty much swaps between two different and discrete cam profiles. Since its a completely different lobe, the timing happens to be different.

Thanks for the support! I'm just sick of people talking about VTEC like its just another system like VANOS (BMW) that simply changes the valve timing while completely ignoring the valve lift part which is what VTEC is about. Here are a few videos to illustrate:

How VTEC Works:
http://www.youtube.com/watch?v=AcT_ZyY3F0k

Toyota's Variable Valve Timing (does not modify valve lift, only timing):
http://www.youtube.com/watch?v=iKo28...eature=related
Another very similar system by Kawasaki:
http://www.youtube.com/watch?v=dSZXepU7Sks&feature=related


One crucial thing to understand is that "Engines with a fixed valve timing can only operate most efficiently and one specific speed". This is why V8 engines with aftermarket "high performance" cams lope at low speeds - they lope because they are tuned for high(er) speeds and are inefficient at idling since they do not employ VVT (First 3 gen Vipers, all Corvettes, Mustangs etc).

To have the ultimate engine that idles well, develops crazy power, and keeps emissions down - it will need ALL of the technologies out there working in sync: Direct Injection, Variable Valve Lift, Variable Valve Timing, and couple it with a pair of small turbos. Or if you're SAAB, you can throw money at Variable Compression as well (good try but..it failed )